Wedged Mortise-Tenon Structure for Fixed Connections in Additive Manufacturing Assemblies Using Fused Filament Fabrication

Wedged Mortise-Tenon Structure for Fixed Connections in Additive Manufacturing Assemblies Using Fused Filament Fabrication | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Wedged Mortise-Tenon Structure for Fixed Connections in Additive Manufacturing Assemblies Using Fused Filament Fabrication Weijun Shen, Pengyu Zhang, Hantang Qin This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8002151/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 24 Feb, 2026 Read the published version in Progress in Additive Manufacturing → Version 1 posted You are reading this latest preprint version Abstract This study investigates the feasibility and performance of wedged mortise–tenon (M–T) joints as fixed connection mechanisms for assemblies fabricated through fused filament fabrication (FFF). By integrating a traditional self-locking joint concept into additive manufacturing, this work aims to provide an alternative to adhesives and mechanical fasteners. This bridges the gap from fabrication to the next-step assembly. An L9 orthogonal experimental design was applied to optimize four geometric parameters of the M–T joint, and the resulting configurations were evaluated through finite element simulation, tensile and flexural mechanical testing, and dimensional accuracy analysis using high-resolution 3D scanning. The optimized design achieved a tensile strength of 5.16 ± 0.66 MPa and flexural strength of 8.13 ± 0.37 MPa, outperforming adhesive-bonded joints in both strength and energy absorption. A dimensional deviation of only 0.026 mm confirmed high printing precision and assembly quality. These results demonstrate that wedged M–T joints offer reliable, strong, and sustainable fixed connections suitable for applications in furniture, automotive, aerospace, and medical device manufacturing. wedged mortise-tenon fused filament fabrication joint design design for additive manufacturing assembly Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Figure 11 Figure 12 1. Introduction Additive manufacturing (AM), rapid prototyping or 3D printing, has transformed the manufacturing landscape by enabling the fabrication of geometrically intricate components with reduced material waste(Brahma et al., 2025 ; Shen, Zhang, et al., 2025 ). Among the various Additive Manufacturing techniques, FFF stands out due to its accessibility and cost-effectiveness. However, the layer-by-layer deposition process characteristic of FFF introduces several challenges, including anisotropy, surface roughness, and dimensional inaccuracies (Crockete et al. , n.d.; Gibson et al., 2021 ; Thompson et al., 2016 ; Xu et al., 2025 ). These inherent limitations significantly impact assembly design, particularly for fixed connections that rely on precise geometry and material properties. Assembly plays a fundamental role in manufacturing, facilitating the creation of complex systems through the integration of discrete components. Over the course of industrial development, a diverse range of fixed connection methods has been developed, including discrete fasteners (e.g., screws and rivets), adhesive bonding, and interlocking mechanisms (Oh et al., 2018 ). Among these, the mortise-tenon (M-T) joint has emerged as a cornerstone of traditional woodworking and mechanical engineering due to its ability to provide strong, durable, and aesthetically pleasing connections without the need for auxiliary hardware (Baptista et al., 2020 ; Hajdarevic et al., 2023 ; Li et al., 2020 ; Schlake et al., 2025 ). Its inherent simplicity and adaptability have rendered it a preferred choice in various applications, from furniture making to architectural frameworks. Despite its historical significance and widespread utility, the potential applications of M-T joints in Additive Manufacturing remain underexplored. The effective connection of parts is crucial for assembly design, influencing both performance and manufacturability. Traditionally, Design for Assembly (DFA) principles guide the choice of connection methods to minimize assembly time and cost while ensuring structural integrity and functionality (Kuo et al., 2001 ; Tuvayanond and Prasittisopin, 2023 ; Wang et al., 2021 ; Zha et al., 2001 ). Conventional methods include discrete fasteners, adhesives, energy bonding, and integral fits, each with specific application requirements and challenges. Discrete fasteners offer modularity and disassembly but increase costs and complexity. Adhesive bonding distributes stress uniformly and eliminates visible connectors but is limited by curing requirements and environmental factors. Energy bonding provides high-strength joints but requires specialized equipment and is constrained by material properties. Integral fits streamline assembly by integrating connection features into part designs, reducing assembly time and hardware needs, though they depend on precision manufacturing and material compatibility (Chaves et al., 2018 ; Cowley et al. , n.d.; Delzendehrooy et al., 2022 ; Lambiase et al., 2021 ; Maggiore et al., 2021 ; Mehta, 2017 ; Song, 2022 ). The rise of Additive Manufacturing introduces new opportunities and challenges, as AM’s ability to create complex geometries and layer materials with high precision demands a reevaluation and adaptation of traditional connection techniques to this new manufacturing paradigm (Liu et al., 2023 ; Mechter et al., 2022 ; Srivastava and Rathee, 2022 ). The use of adhesives in Additive Manufacturing has been extensively studied to address the limitations of mechanical connections and enhance the structural integrity of AM printed parts (Khosravani et al., 2023 ; Pradel et al., 2018 ; Wei et al., 2024 ). Golewski, Sadowski, and Nowicki highlighted the advantages of using 3M™ VHB™ 5925 double-sided adhesive tape for bonding additively manufactured AM polymer adherends, noting its ability to preserve structural integrity, conform to rough surfaces, simplify the joining of complex geometries, and distribute loads evenly. However, they also identified limitations such as insufficient shear strength for high-load applications and the viscoelastic nature of adhesives, which can impair joint longevity (Golewski et al., 2023 ). Similarly, Garcia and Prabhakar demonstrated that deposited adhesive layers could significantly enhance bond strength and stiffness in single-lap joints, although the effectiveness depended on proper surface preparation and material compatibility (Garcia and Prabhakar, 2017 ). The integration of effective joining methods in AM process is crucial for enhancing the structural integrity and functionality of AM components. The challenges in joining dissimilar fabricated parts and the limitations of conventional techniques for complex geometries have led researchers to explore new joining methods. Mechanical fasteners for AM printed parts are an emerging technique with distinct advantages and limitations. Unlike adhesive joining, mechanical fastening requires no surface preparation and allows for easy inspection and disassembly, except in the case of rivets. Additionally, mechanical fastening avoids thermal degradation issues associated with excessive heating in other joining methods. However, mechanical fasteners increase component weight and induce stress around the fastener holes, which can reduce strength and lead to corrosion. The process can also be labor-intensive, involving additional fixtures and stages such as heating and inserting fasteners, which may damage and weaken the surrounding structure. Despite its simplicity, there is limited research on joining AM parts using mechanical fasteners. Hybrid joints combining mechanical fasteners and adhesives have not yet been extensively studied or reported. Fahreddin Fatih Öngül, İlyas Kandemir, and Esma Pala Öngül conducted a study on adhesive and glue applications in Additive Manufacturing implements, specifically focusing on fasteners within the Fused Deposition Modeling (FDM). They investigated common fastener methods for FDM-manufactured parts, identifying factors influencing tensile and bending strengths using various design techniques and infill ratios, with Polylactic Acid (PLA) as the primary material. The study examined four fastening methods, including heat-set inserts and embedded square nuts, to enhance structural integrity and optimize assembly methodologies. Test samples with different infill ratios were designed to comprehensively test tensile, flexural, and tightening torque strengths. Findings revealed that the adhesion strength of heat-set inserts is significantly influenced by infill ratio, while embedded nut methods showed varying load responses, highlighting the importance of wall thickness. Despite advancements, the study acknowledged limitations of conventional adhesives in FDM, such as lower mechanical strength of plastics compared to metals and reduced strength due to surface roughness from the layer-by-layer nature of FDM. The research emphasizes the need for innovative materials and techniques to improve adhesive applications for high-stress applications. These insights advance understanding of adhesive applications in FDM and pave the way for optimized fastening techniques in specialized fields like aerospace and medical industries, highlighting the necessity for tailored solutions considering mechanical properties, production efficiency, and practical application needs (Öngül et al., 2024 ; Zhang et al., 2022 ). The exploration of M-T joints in Additive Manufacturing is particularly relevant to industries requiring lightweight, modular, and disassemblable structures. For example, in aerospace and automotive sectors, components often demand high strength-to-weight ratios and ease of assembly without adhesives or metal fasteners, which add weight and complexity. Similarly, in furniture design, M-T joints enable glue-free assembly of AM fabricated parts, aligning with sustainability goals by simplifying recycling and reducing material waste. Medical device manufacturing also benefits from such joints, where biocompatible materials like PLA can form sterilizable, snap-fit connections for prosthetics or surgical tools. These applications underscore the need for robust, printable joints that bypass traditional joining limitations while leveraging AM’s geometric flexibility. The advancement of Additive Manufacturing has revolutionized the design and assembly of complex structures, necessitating innovative connection and joining methods. Traditional techniques such as discrete fasteners, adhesive bonding, energy bonding, and integral fits have been foundational, but AM introduces new opportunities and challenges. Luo et al. developed the Chopper framework, which uses Binary Space Partitioning (BSP) trees to segment objects into smaller parts, ensuring effective alignment and interconnection through well-designed connectors (Luo et al., 2012 ). Song et al. introduced a voxelization-based method for creating interlocking 3D parts from complex shapes, facilitating robust connections through the development of connection graphs (Song et al., 2015 ). Xin et al. focused on generating multi-knot burr puzzles, employing a knot network framework and a greedy algorithm to construct intricate assemblies of interlocking pieces (Xin et al., 2011 ). Despite the advancements, challenges remain, such as optimizing for multiple conflicting goals, translating complex geometries into effective interlocking features, and achieving non-orthogonal connections. These studies highlight the critical balance between structural integrity and design complexity in generating functional AM assemblies. Interlocking mechanisms excel in AM environments because they eliminate the need for additional hardware or adhesives, reduce assembly time, and exploit the geometric complexity achievable. However, they require careful design consideration to ensure structural integrity and ease of assembly/disassembly. These traditional and emerging methods highlight the diverse approaches available for assembling AM fabrciated parts (see Fig. 1 ). By leveraging these techniques, designers can address the specific challenges posed by Additive Manufacturing processes, paving the way for more efficient and functional assemblies. The integration of interlocking designs, such as M-T joints, represents a promising avenue for enhancing fixed connections, combining strength, simplicity, and the unique design opportunities of Additive Manufacturing. The M-T joint, a centuries-old design, traditionally consists of a protruding tenon inserted into a corresponding mortise, forming a secure interlocking connection without external fasteners. This simplicity aligns with the goals of Additive Manufacturing to minimize material use and auxiliary components, making it an ideal candidate for exploration within the domain of FFF. The adaptability of M-T joints allows for customization to meet specific load-bearing and aesthetic requirements. This adaptability is further amplified by the geometric freedom inherent in AM, enabling the design of advanced features such as dovetail joints, cylindrical tenons, and reinforced mortises to optimize stress distribution and mechanical performance. However, adapting M-T joints for FFF introduces several challenges. The success of such joints in traditional manufacturing depends heavily on precise machining and consistent material properties. In FFF, the layer-by-layer process introduces surface imperfections, dimensional deviations, and internal defects, all of which can compromise the fit and structural integrity of the joint. Additionally, the anisotropic mechanical properties of FFF-printed parts can lead to uneven load distribution, further complicating the performance of these joints. Addressing these challenges requires a comprehensive investigation into the design and optimization of M-T joints specifically tailored for FFF. This research aims to explore the feasibility and performance of wedged M-T joints as a fixed connection method in Additive Manufacturing, with a particular emphasis on FFF. The primary objectives are to develop optimized designs that address challenges such as mechanical performance, dimensional precision, and printability; evaluate the mechanical performance of these joints under various loading conditions, including tensile and flexural forces; and provide practical guidelines for their implementation in Additive Manufacturing assemblies, considering factors such as material selection, joint geometry, and printing parameters. This study introduces innovative M-T designs compatible with FFF technology, experimentally validating their mechanical properties and feasibility. Figure 2 illustrates the flow of this proposed work, highlighting the formulation of design and manufacturing guidelines for broader adoption. These guidelines specifically address the unique challenges posed by FFF while harnessing its capabilities effectively. By overcoming the limitations of the build volume associated with commercially available 3D printers, this research significantly enhances the applicability and efficiency of AM process across various industrial contexts. The integration of these advancements aims to expand assembly design within Additive Manufacturing, paving the way for sustainable, efficient, and functional manufacturing solutions across diverse sectors, including furniture design, construction, automotive, and aerospace. By tackling the technical challenges inherent to FFF and its build volume constraints, this study broadens the practical applications of AM, positioning it as a more viable and efficient option for a wide range of industries. 2. Design and Methodology The design of M-T joints for FFF was developed with a primary focus on optimizing geometric parameters to achieve superior mechanical performance. These objectives were carefully balanced against the unique constraints of FFF processes, such as anisotropy in material properties, the layer-by-layer fabrication method, and the need for efficient material and time usage. The key considerations driving the design included maximizing joint strength, ensuring ease of manufacturability, and minimizing the use of support material to improve overall printability and reduce post-processing requirements. Drawing inspiration from traditional woodworking, the overall design adopts a wedged M-T structure, which provides enhanced mechanical interlocking through its self-locking capabilities under load. The wedged tenon, a hallmark of woodworking joints, was adapted for FFF by incorporating a kerf, or slit, into the tenon. This kerf allows for controlled deformation during assembly, enabling a tighter fit without inducing excessive stress on the joint or surrounding material. Additionally, the mortise incorporates a relief zone specifically designed to facilitate the slight deformation of the tenon structure. This deformation allows the tenon to interlock securely with the mortise through an interference fit, ensuring a robust and stable connection. 2.1 Mortise-Tenon Joint Design for FFF The geometry of the tenon in the wedged M-T joint was carefully designed to enhance self-locking behavior, thereby improving load-bearing capacity and assembly stability without the need for additional fasteners or adhesives (Baleanu et al., 2015 ). Key design parameters were considered, including the tenon width, length, thickness, and the angle of the mortise relief area, each of which plays a vital role in the mechanical performance and manufacturability of the joint (Abdelrahman et al., 2017 ). As shown in Fig. 3 Error! Reference source not found. , the tenon width (W) influences the overall strength of the joint by determining the contact area between the tenon and mortise. A wider tenon generally increases the surface area for load distribution, improving the joint’s strength, but it must be optimized to balance material usage and printability. The tenon length (L) is another critical parameter that governs the joint’s resistance to pull-out forces. A longer tenon enhances the joint’s strength, particularly under tension, by increasing the surface area over which forces are distributed. However, excessively long tenons can lead to challenges during the assembly process and may reduce printability due to the complexity of the geometry. The tenon thickness (T) directly impacts the joint’s ability to resist compression and tension. A thicker tenon is more robust under load, but if it is too thick, it can increase the potential for material deformation and failure during printing, especially in FFF processes where the layer-by-layer deposition method can introduce weak interfaces between layers. The mortise relief area angle (θ) is another essential parameter that impacts the fit between the mortise and tenon. The relief area reduces stress concentration during assembly, facilitating a tighter fit and improving the overall strength of the joint. The angle of this relief zone must be optimized to ensure the joint’s performance under mechanical loading while accounting for the dimensional variations inherent in FFF fabrication. Table 1 L9 orthogonal array for four geometric parameters at three levels. Run L [mm] W [mm] T [mm] θ [°] von Mises [MPa] 1 8 7.5 2.5 10 3.35 2 8 10 3.75 12.5 3.95 3 8 12.5 5 15 2.95 4 10 7.5 3.75 15 5.13 5 10 10 5 10 1.88 6 10 12.5 2.5 12.5 3.21 7 12 7.5 5 12.5 3.14 8 12 10 2.5 15 4.94 9 12 12.5 3.75 10 2.92 The design parameters of the M-T joints—width (W), length (L), thickness (T), and angle (θ)— were systematically determined and optimized using an orthogonal array experimental design, a robust method for efficiently evaluating multiple factors with minimal experimental runs (Ranjit K. Roy, 2001 ). This approach is widely used in additive manufacturing studies to balance parameter interactions, optimize performance metrics (Chohan et al., 2022 ; Khalid and Peng, 2021 ). The orthogonal array selected for this study, shown in Table 1 Error! Reference source not found. , encompasses nine experimental runs, each representing a unique combination of the design parameters at three levels. The parameter levels were chosen to reflect practical constraints and achievable dimensions within the capabilities of FFF while covering a sufficient range to identify meaningful trends. The orthogonal array enables a systematic evaluation of the effects of each parameter and their interactions on the mechanical performance of the joint, including strength, stiffness, and toughness. Each joint configuration will be fabricated using the same FFF process parameters to ensure consistency across tests. The finite element simulations were conducted using a linear elastic material model for PLA, assuming isotropic behavior to simplify the analysis. The PLA material properties were defined based on preliminary tensile tests and literature values. The model employed 3D solid tetrahedral elements (C3D10) to accurately capture the complex geometry of the mortise-tenon joints. Boundary conditions were applied by fully constraining the base of the mortise component, while a displacement-controlled load was applied to the tenon end to simulate tensile loading. Tensile properties were initially evaluated through finite element simulation for each parameter configuration. The simulation results, shown in Fig. 4 a, highlighted the regions of maximum stress concentration under tensile loading. Subsequent mechanical testing of the fabricated samples validated the simulation results. Images of the failure modes (Fig. 4 b) confirmed that the areas of failure during physical testing corresponded precisely with the high-stress regions identified in the simulation. This agreement between simulation and experimental observations demonstrates the effectiveness of the orthogonal array approach for optimizing the design parameters and highlights the reliability of the simulation tools in predicting mechanical behavior. The optimized design parameters (W = 12 mm, L = 7.5 mm, T = 3.75 mm, and θ = 15°) derived from simulation results (see Table 2 ) are expected to maximize the mechanical performance of the M-T joint while addressing the inherent constraints of FFF, including the layer-by-layer fabrication process and potential geometric deviations. Figure 5 and Fig. 6 illustrate the finalized design for the tensile and flexural samples, which were subsequently fabricated and subjected to mechanical testing for both tensile and flexural properties, further validating the optimization process. Table 2 Comparison of factors and levels to identify the optimized parameter combination. Factor L [mm] W [mm] T [mm] θ [°] Level 1 3.42 3.87 3.83 2.72 2 3.41 3.59 4.00 3.44 3 4 3.67 12 3.03 7.5 2.66 3.75 4.341 15 2.2 Material Selection and Printing Parameters The selection of materials is critical in determining the performance of the M-T joints. Preliminary tensile tests were conducted on samples printed using three commonly used FFF materials: ABS, PLA, and PETG. The tests carried out at a speed of 6 mm/min, revealed notable differences in tensile strength: PETG exhibited the highest tensile strength at 273 MPa, followed by PLA at 253 MPa and ABS at 107 MPa. Despite PETG’s superior tensile strength, PLA was chosen for the joint design due to its comparable strength, better printability, lower warping tendency, and ease of use in various printing conditions. PLA’s suitability is further supported by its widespread adoption in FFF research and industrial applications, where it balances stiffness and tensile strength comparable to engineering-grade polymers, making it ideal for structural joints(Gibson et al., 2021 ). Its low warping tendency and minimal shrinkage ensure dimensional stability, critical for precise interference fits in M-T joints (Alzyod and Ficzere, 2023 ; Shen et al., 2025 ). Environmentally, PLA’s biodegradability aligns with sustainable manufacturing goals, as emphasized in lifecycle assessments of AM materials (Rezvani Ghomi et al., 2021 ). In addition to tensile strength, ductility and toughness were evaluated based on elongation at break and energy absorption during tensile testing. PETG exhibited the highest elongation at break (12.4%), followed by ABS (8.7%) and PLA (4.3%), confirming its superior ductility. Toughness, estimated from the area under the stress-strain curve, also followed this trend. However, PETG was less favorable due to its complex printing characteristics and tendency to warp. ABS demonstrated moderate toughness and better thermal resistance but suffered from layer adhesion issues. PLA, while less ductile, provided the best dimensional stability and print consistency, making it the most suitable choice for the M-T joint application. Figure 7 compares the tensile strength performance of ABS, PLA, and PETG, providing a clear illustration of the material properties that influenced the selection process. These material properties—along with optimized printing parameters—were crucial factors in ensuring that the M-T joints would perform reliably under expected loading conditions while maintaining manufacturability in an FFF process. The performance of the M-T joints was influenced by the selection of key printing parameters, which were carefully optimized to balance joint strength and manufacturing feasibility. The prints were produced using the Original Prusa MK4S with a 0.4 mm nozzle, ensuring precision and reliability. These parameters ensured consistent mechanical properties, material efficiency, and ease of production within the constraints of FFF technology. A finer layer height and appropriate infill density contributed to smooth layer bonding and adequate internal structure, while standard extrusion settings for PLA maintained optimal material flow and adhesion. Preliminary testing confirmed that tensile speed had minimal influence on joint strength, validating the sufficiency of these standard settings for achieving high-quality prints. Table 3 summarizes the printing parameters used for all sample preparations. Table 3 Printing parameters for all sample preparation with PLA. Parameter Value Nozzle temperature [°C] 210 (215 for first layer) Bed temperature [°C] 60 Layer height [mm] 0.10 (0.15 for first layer) Infill pattern [-] Rectilinear Infill density [%] 20 2.3 Testing Procedures Mechanical Testing: All mechanical tests were conducted in accordance with relevant ASTM standards. Tensile and 3-point flexural tests were conducted to assess joint strength and stiffness. For tensile test, specimen is gripped firmly by each end of the testing machine and aligned so that there would not be bending forces during the test. For flexural test, specimen is placed on two parallel supports at a distance apart, the load would be applied at the center between the supports. Load would be increased until the specimen fractures in both tests. To examine the influence of testing speed on tensile performance, initial tests (see Fig. 8 ) were conducted at speeds of 6 mm/min, 30 mm/min, and 60 mm/min. The results showed no significant differences in joint performance across these speeds, confirming that testing speed had a negligible effect on strength. Based on these findings, a speed of 60 mm/min was selected for tensile testing. The flexural tests simulated real-world bending forces and were conducted at a speed of 10 mm/min with a span length of 3 inches to measure joint stiffness and bending resistance effectively. For comparison, all mechanically tested samples were evaluated against adhesive-bonded samples prepared using SUPER GLUE Instant Adhesive, which has a reported tensile strength of 17.2 Mpa (2500 psi) according to its datasheet. These adhesive-bonded samples were cured for at least 24 hours prior to testing, ensuring reliable baseline performance for comparison with the M-T joints. During tensile testing, the mortise and tenon components were aligned such that the applied load acted axially along the length of the tenon, simulating a direct pull-out scenario. This ensured that the joint experienced pure tensile stress without bending. For flexural testing, the assembled joint was positioned horizontally with the tenon spanning across the supports and the mortise located centrally under the loading nose, allowing the joint to experience bending stress perpendicular to the tenon axis. This setup was designed to evaluate the joint’s resistance to shear and bending forces under realistic loading conditions. Dimensional Accuracy: Dimensional accuracy was evaluated using the Revopoint POP2 3D scanner, featuring a resolution of 0.015 mm, to ensure the printed joints met required tolerances and assembly precision. Flexural test samples were chosen for scanning due to their larger surface area, which amplifies the impact of any discrepancies on the overall Cloud-to-Mesh (C2M) distance analysis. For each sample, the top, bottom, and two side surfaces were scanned to provide comprehensive geometric coverage. The scanned point cloud data was processed and reconstructed using Revo Studio, ensuring high-quality and accurate representations of the sample geometries. The C2M distance analysis was conducted with CloudCompare v2.12.4, which allowed for precise comparisons between the reconstructed point clouds and the nominal CAD mesh models. 3. Results and Discussion 3.1 Mechanical Performance Analysis The mechanical performance of the M-T (M-T) joints was evaluated through tensile and flexural testing to provide a comprehensive assessment of their strength, stiffness, and toughness in comparison to glued joints. These tests also served to examine the influence of the joint geometry and FFF parameters on mechanical behavior. The standard deviations for all mechanical properties were estimated using the Student’s t-distribution due to the limited sample size, ensuring statistical robustness. Tensile Testing Tensile tests were conducted to compare the load-bearing capacity and failure modes of glued and M-T joints under uniaxial loading. Table 4 summarizes the results, and the mechanical properties are further illustrated in Fig. 9 . Table 4 Tensile test results of adhesive and M-T joining, with standard deviation estimates using Student’s T-Distribution (95% confidence level). Strength [Mpa] Std. Dev. [±] Stiffness [N/mm] Std. Dev. [±] Toughness [J/cm3] Std. Dev. [±] Adhesive Joining 2.46 1.00 1033.25 176.47 69.19 32.33 M-T Joining 5.16 0.66 146.08 16.10 4429.02 556.33 The M-T joints exhibited a tensile strength of 5.16 ± 0.66 MPa, more than double that of the glued joints (2.46 ± 1.00 MPa), as shown in Fig. 9 a. The marked improvement can be attributed to the self-locking interlocking geometry of the M-T joints, which enables a more efficient transfer of tensile loads across the joint interface. In contrast, the glued joints depend on the adhesive’s shear strength, which becomes a limiting factor under tensile loading. The relatively small standard deviation for the M-T joints indicates consistent manufacturing quality and performance, whereas the higher variability observed for the glued joints suggests potential inconsistencies in adhesive application or bonding quality. These findings reinforce the reliability of the M-T design over traditional adhesive joints in tensile loading scenarios. In Fig. 9 b, the glued joints demonstrated a significantly higher tensile stiffness of 1033.25 ± 176.47 N/mm compared to 146.08 ± 16.10 N/mm for the M-T joints. This discrepancy highlights a trade-off inherent in the M-T design: while the glued joints provide rigidity, the M-T joints allow for controlled deformation, which can be beneficial in applications requiring flexibility or energy dissipation. The lower stiffness of the M-T joints could also be linked to the inherent anisotropy of FFF parts, particularly in layer bonding and the kerf slit design. Although this reduced stiffness may seem disadvantageous for static load-bearing applications, it enhances the joints’ toughness, as discussed below. The M-T joints outperformed the glued joints significantly in tensile toughness as depicted in Fig. 9 c, achieving 4429.02 ± 556.33 J/cm³ compared to the glued joints’ 69.19 ± 32.33 J/cm³. The high toughness reflects the M-T joints’ ability to absorb and dissipate energy, making them highly suitable for dynamic or impact loading conditions. This behavior is attributed to the joint’s ability to distribute stresses more evenly, reducing the likelihood of brittle failure observed in glued samples. The toughness advantage of M-T joints aligns with their observed failure modes. The M-T joints primarily failed through gradual layer delamination, providing a warning before ultimate failure, whereas the glued joints exhibited sudden adhesive failure, which is less desirable in practical applications. Flexural Testing Flexural tests were conducted to evaluate the bending performance of M-T joints compared to glued joints. The properties measured include flexural strength, modulus, toughness, and strain at failure. The results, summarized in Table 5 and depicted in Fig. 10 , reveal significant differences in the mechanical response of the two joint types, reflecting the distinct mechanisms through which they resist bending loads. Table 5 Flexural test results of adhesive and M-T joining, with standard deviation estimates using Student’s T-Distribution (95% confidence level). Flexural Strength [Mpa] Std. Dev. [±] Flexural Modulus[MPa] Std. Dev. [±] Flexural Strain [-] Std. Dev. [±] Toughness [J/cm 3 ] Std. Dev. [±] Adhesive Joining 5.157 1.408 374.64 80.37 0.012 0.003 103.81 54.44 M-T Joining 8.126 0.370 222.18 12.40 0.050 0.010 945.10 190.68 The M-T joints achieved a flexural strength of 8.126 ± 0.370 MPa, outperforming the glued joints, which reached only 5.157 ± 1.408 MPa. This represents a 57.5% increase in bending strength for the M-T joints. The lower variability in the M-T samples (standard deviation of 0.370 MPa) compared to the glued joints (1.408 MPa) suggests that the interlocking design of the M-T joints enhances repeatability and reliability. The superior strength of the M-T joints can be attributed to the wedged interlocking mechanism, which effectively distributes bending stresses along the joint interface. In glued joints, failure is localized at the adhesive bond, where stress concentration leads to abrupt failure, whereas the M-T design facilitates progressive load sharing across the tenon and mortise. The glued joints exhibited a flexural modulus of 374.641 ± 80.373 MPa, significantly higher than the M-T joints’ 222.181 ± 12.400 MPa, indicating that glued joints are stiffer under bending loads. However, the higher stiffness of the glued joints comes at the expense of energy absorption capacity, as discussed below. The reduced modulus of the M-T joints suggests greater flexibility, enabling them to deform more under bending stresses without immediate failure. This characteristic is particularly advantageous for applications requiring joints to withstand dynamic or repetitive loading, as it allows the M-T joints to accommodate minor displacements without significant loss of structural integrity. The toughness, representing the energy absorbed during bending, was substantially higher in the M-T joints (945.103 ± 190.680 J/cm³) than in the glued joints (103.813 ± 54.441 J/cm³). This indicates that the M-T joints absorbed 811% more energy before failure compared to the glued joints. The exceptional toughness of the M-T joints reflects their ability to undergo controlled deformation before failure. Observations during testing revealed gradual delamination and bending of the tenon in the M-T samples, which allowed them to sustain higher loads for longer durations. In contrast, the glued joints exhibited brittle failure, with abrupt adhesive bond separation leading to a catastrophic drop in load-bearing capacity. The maximum flexural strain for the M-T joints was 0.05 ± 0.01, significantly higher than the glued joints’ 0.012 ± 0.003. This represents a 316% increase in strain capacity, emphasizing the ductility of the M-T joints. The ability to accommodate greater strain without failure highlights the robustness of the M-T joints under bending stresses. The wedged design and relief zones likely contribute to this behavior by mitigating stress concentrations and allowing for controlled deformation. Conversely, the limited strain capacity of the glued joints is indicative of their brittle failure mechanism, where bond failure occurs at relatively small displacements. 3.2 Geometric Accuracy To evaluate the alignment and assembly accuracy of the M-T joints, the assembled surfaces were scanned using a high-resolution Revopoint POP2 3D scanner, and the resulting point cloud data was processed in CloudCompare v2.12.4. The C2M distance method(Lague et al., 2013 ) was employed to quantify geometric discrepancies by comparing the scanned assembly surfaces (target) to the nominal CAD surfaces (reference). The C2M analysis generated a distance map, highlighting deviations at each point on the reference surface and producing an average distance metric that quantified the overall alignment error. For this study, the average C2M distance was 0.026 ± 0.006 mm for the top and bottom surfaces and 0.025 ± 0.008 mm for the side faces, as shown in Fig. 11 . These results demonstrate a high degree of alignment precision, especially considering the limitations inherent to the FFF printing process, such as a nozzle diameter of 0.4 mm and a layer thickness of 0.1 mm. The observed alignment accuracy, well within the expected tolerance limits for FFF, underscores the effectiveness of the M-T design and the manufacturing parameters in achieving accurate fits. This precision is critical to ensuring both the mechanical performance and structural integrity of the assembled joints. 3.3 Discussion The mechanical testing results highlight significant performance differences between M-T joints and glued joints, showcasing the advantages of the M-T design in both tensile and flexural loading scenarios. Tensile tests indicate that M-T joints possess superior load-bearing capacity and energy absorption compared to their glued counterparts. Although glued joints may demonstrate greater stiffness, their brittleness hinders toughness, resulting in sudden failure when the adhesive bond is compromised. Conversely, M-T joints utilize their interlocking geometry to effectively distribute stresses, leading to controlled and progressive failure modes. This property makes them particularly suitable for applications where strength and reliability are crucial. Flexural testing further supports these findings, revealing that M-T joints can endure higher bending loads and greater deformations before failure. While glued joints exhibit higher stiffness, they lack the strain capacity and toughness that M-T joints provide. The wedged interlocking design of the M-T joints enhances stress distribution under bending forces, decreasing the likelihood of sudden failure and enabling greater energy absorption. Analyzing the failure modes (see Fig. 12 ) offers additional insights into these mechanical behaviors. Observations of M-T joint failures reveal a combination of delamination and material deformation in both tensile and flexural tests, indicative of a progressive and controlled failure mechanism. In contrast, glued joints primarily fail at the adhesive interface, resulting in sudden and catastrophic breakdowns. These contrasting failure patterns highlight the improved reliability and safety of the M-T design, which is better equipped to withstand dynamic or high-strain loading conditions. The surface comparison results further show that the M-T joints achieved notable dimensional accuracy, with average C2M distances of 0.026 mm for the top and bottom surfaces and 0.025 mm for the side faces—values that are well within the expected tolerance for FFF printing using a 0.4 mm nozzle and a 0.1 mm layer height. This suggests that the selected printing parameters, including layer height and infill density, effectively minimized distortions and ensured precise alignment. The small average C2M distances indicate a snug fit between the mortise and tenon components, which is critical for load distribution and overall joint strength. These results confirm the feasibility of employing FFF for creating mechanically reliable assemblies, as minimal misalignment reduces the risk of stress concentrations that could jeopardize performance. While the achieved accuracy is encouraging, minor surface irregularities typical of FFF printing may still impact assembly quality. Future studies could investigate additional process optimizations to further enhance dimensional precision. In summary, these findings demonstrate that M-T joints are a mechanically superior alternative to glued joints, especially in applications requiring strength, toughness, and controlled failure behavior. The results lay a strong groundwork for future investigations into M-T joint designs, including potential optimizations and material modifications, aimed at expanding their applicability in Additive Manufacturing and structural systems. Furthermore, the comparison of point clouds affirms that, with the right optimizations, FFF printing can yield precise and structurally robust mechanical joints. 4. Conclusion and Future Work This research has successfully demonstrated the viability and effectiveness of M-T joints as a fixed connection method in FFF, offering a robust alternative to traditional joining methods such as adhesive bonding and mechanical fasteners. The study directly addresses the critical challenges of overcoming build volume limitations and enhancing AM’s industrial applicability, while providing designers with an additional option for creating reliable assemblies in Additive Manufacturing. Through systematic optimization of joint geometry and careful consideration of FFF-specific constraints, the M-T design offers a balance of strength, precision, and manufacturability that makes it particularly well-suited for applications requiring both structural integrity and ease of assembly. Mechanical testing demonstrated the superior performance of M-T joints compared to traditional glued joints. M-T joints exhibited a tensile strength of 5.16 ± 0.66 MPa, more than double that of glued joints (2.46 ± 1.00 MPa). While glued joints showed higher tensile stiffness (1033.25 ± 176.47 N/mm vs 146.08 ± 16.10 N/mm), M-T joints demonstrated superior toughness and more controlled failure modes, making them more reliable for structural applications. The interlocking geometry effectively distributed stresses, resulting in progressive failure through delamination and material deformation rather than the sudden catastrophic failures observed in glued joints. Besides, alte rnative build orientations could significantly influence the mechanical performance of the joints. Printing the joint horizontally (with the tenon axis aligned in the XY plane) would align the layer lines with the loading direction, potentially improving tensile strength due to stronger in-layer bonding. However, this may introduce dimensional inaccuracies or require more support material. Similarly, changing the load alignment to act along the layer lines could reduce strength due to weaker interlayer adhesion. Dimensional accuracy analysis using high-resolution 3D scanning and C2M comparison revealed excellent precision, with average deviations of 0.026 mm for top/bottom surfaces and 0.025 mm for side faces. These results, achieved using a 0.4 mm nozzle and 0.1 mm layer height, demonstrate the capability of FFF to produce precise mechanical joints when properly optimized. However, this study has limitations that warrant acknowledgment: The focus on PLA material and specific printing parameters may not generalize to diverse industrial requirements. Mechanical testing was limited in sample size and loading/environmental conditions, which could affect real-world applicability. The resolution of 3D scanning equipment constrained dimensional accuracy assessments. Future research should prioritize: Developing design guidelines tailored to industrial applications (e.g., aerospace, construction). Integrating advanced post-processing techniques to enhance joint performance. Exploring hybrid methods combining M-T joints with adhesives or fasteners. Improving quality control protocols for dimensional accuracy. The practical implications of this work extend to several emerging fields. In sustainable architecture, M-T joints enable the assembly of large-scale AM fabricated structures (e.g., partitions, façades) without adhesives, simplifying material recovery and reuse. For consumer electronics, printed casings with integrated M-T connectors could eliminate screws, reducing part count and assembly time. Additionally, the medical industry could adopt these joints for patient-specific devices, such as orthotic braces, where PLA’s biocompatibility and the joints’ reconfigurability allow for customizable, hygienic solutions. By addressing the limitations of conventional joining methods in these domains, the study advances AM toward broader industrial adoption, ensuring that research outcomes translate into tangible societal and economic benefits. These findings advance Additive Manufacturing assembly methods by demonstrating the viability of M-T joints in FFF. Future research could build on this work by developing industry-specific design guidelines, integrating hybrid joining techniques, and refining quality control protocols to create more efficient, sustainable, and reliable solutions. The success of M-T joints in this study highlights their potential to address current limitations in AM technology, such as build volume constraints, and could enable more complex, large-scale manufacturing applications in sectors like aerospace and modular construction. 5. Data availability statement Data will be made available on request. 6. Disclosure statement No potential conflict of interest was reported by the author(s). Declarations Author Contribution Weijun Shen designed the structure and finished 70% of the experiment and testing. Pengyu Zhang finished the least part of the experiment. Weijun Shen and Pengyu Zhang wrote the main manuscript, all the figures, and tables. All the authors reviewed the manuscript. 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J Eng Des 1–16. 10.1080/09544828.2025.2576424 Zha XF, Du HJ, Qiu JH (2001) Knowledge-based approach and system for assembly oriented design, Part I: the approach. Eng Appl Artif Intell 14(1):61–75. 10.1016/S0952-1976(00)00060-9 Zhang J, Van Hooreweder B, Ferraris E (2022) Fused Filament Fabrication on the Moon, JOM , Springer, Vol. 74 No. 3, pp. 1111–1119. 10.1007/S11837-021-05031-Z/FIGURES/5 Additional Declarations No competing interests reported. Cite Share Download PDF Status: Published Journal Publication published 24 Feb, 2026 Read the published version in Progress in Additive Manufacturing → Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-8002151","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":550136936,"identity":"103282c5-566a-4156-8e40-95f0c4c0e628","order_by":0,"name":"Weijun Shen","email":"","orcid":"","institution":"University of Wisconsin–Madison","correspondingAuthor":false,"prefix":"","firstName":"Weijun","middleName":"","lastName":"Shen","suffix":""},{"id":550136938,"identity":"d868a5db-d41b-4745-be6e-29a7941f7069","order_by":1,"name":"Pengyu Zhang","email":"","orcid":"","institution":"University of 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1","display":"","copyAsset":false,"role":"figure","size":234842,"visible":true,"origin":"","legend":"\u003cp\u003eVarious methods for joining AM fabricated components.\u003c/p\u003e","description":"","filename":"Picture1.png","url":"https://assets-eu.researchsquare.com/files/rs-8002151/v1/b129dab6299a47107d3da641.png"},{"id":96824985,"identity":"3a07daa7-430b-4b60-84e4-b15326953e51","added_by":"auto","created_at":"2025-11-26 12:39:07","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":337680,"visible":true,"origin":"","legend":"\u003cp\u003eWorkflow of this proposed study.\u003c/p\u003e","description":"","filename":"Picture2.png","url":"https://assets-eu.researchsquare.com/files/rs-8002151/v1/07b2838a9f1ee19884b1946c.png"},{"id":96918966,"identity":"e5dbbe83-cda9-4d57-8413-9631ccfa833d","added_by":"auto","created_at":"2025-11-27 14:12:54","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":306663,"visible":true,"origin":"","legend":"\u003cp\u003eGeometric parameters of the M-T joint design.\u003c/p\u003e","description":"","filename":"Picture3.png","url":"https://assets-eu.researchsquare.com/files/rs-8002151/v1/09be88ca0c5028cf4bd63f60.png"},{"id":96824952,"identity":"39261f7b-b006-4f6b-9f04-1776b5dd72b5","added_by":"auto","created_at":"2025-11-26 12:39:06","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":292841,"visible":true,"origin":"","legend":"\u003cp\u003eSimulation results and failure modes under tensile loading: a) Simulation results showing regions of maximum stress concentration, and b) Tensile test results with failure modes matching high-stress regions from the simulation.\u003c/p\u003e","description":"","filename":"Picture4.png","url":"https://assets-eu.researchsquare.com/files/rs-8002151/v1/d0ceadc20b0612ea0322dcdf.png"},{"id":96825003,"identity":"03a812b6-7f8b-4a52-9b50-7017e5c12b62","added_by":"auto","created_at":"2025-11-26 12:39:08","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":241594,"visible":true,"origin":"","legend":"\u003cp\u003eSample design for the tensile test: a) Tenon member, b) Mortise member, and c) Sample for adhesive bonding test.\u003c/p\u003e","description":"","filename":"Picture5.png","url":"https://assets-eu.researchsquare.com/files/rs-8002151/v1/3322ea81aa80923904166f90.png"},{"id":96824981,"identity":"7ae4e248-e7e5-4cc6-ac8b-a8d971380d93","added_by":"auto","created_at":"2025-11-26 12:39:07","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":214841,"visible":true,"origin":"","legend":"\u003cp\u003eSample design for the flexural test: a) M-T members, and b) Sample for adhesive bonding test.\u003c/p\u003e","description":"","filename":"Picture6.png","url":"https://assets-eu.researchsquare.com/files/rs-8002151/v1/bc28e7937529e33e69ea1992.png"},{"id":96824970,"identity":"40d32109-0bb9-40b7-9322-982ee3513113","added_by":"auto","created_at":"2025-11-26 12:39:06","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":57640,"visible":true,"origin":"","legend":"\u003cp\u003eTensile strength comparison of ABS, PLA, and PETG.\u003c/p\u003e","description":"","filename":"Picture7.png","url":"https://assets-eu.researchsquare.com/files/rs-8002151/v1/48e7576fe627c6737f736809.png"},{"id":96918072,"identity":"dd061449-66f4-452d-b701-d9116d2fc76f","added_by":"auto","created_at":"2025-11-27 14:11:08","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":29209,"visible":true,"origin":"","legend":"\u003cp\u003eInitial test of speed rate on tensile performance of M-T joint samples.\u003c/p\u003e","description":"","filename":"Picture8.png","url":"https://assets-eu.researchsquare.com/files/rs-8002151/v1/9e697ea994658a0372b9b346.png"},{"id":96824953,"identity":"e62edbbf-aa4f-425e-9253-44b8221273aa","added_by":"auto","created_at":"2025-11-26 12:39:06","extension":"png","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":119619,"visible":true,"origin":"","legend":"\u003cp\u003eTensile results for adhesive glued and M-T jointed samples: a) tensile strength, b) tensile stiffness, and c) tensile toughness.\u003c/p\u003e","description":"","filename":"Picture9.png","url":"https://assets-eu.researchsquare.com/files/rs-8002151/v1/6235a06417f6c7c5c50784ab.png"},{"id":96824969,"identity":"91a35517-75ab-4994-9165-53f7d0713d7f","added_by":"auto","created_at":"2025-11-26 12:39:06","extension":"png","order_by":10,"title":"Figure 10","display":"","copyAsset":false,"role":"figure","size":108510,"visible":true,"origin":"","legend":"\u003cp\u003eFlexural test results for adhesive glued and M-T jointed samples: a) flexural strength, b) flexural modulus, c) flexural toughness, and d) flexural strain.\u003c/p\u003e","description":"","filename":"Picture10.png","url":"https://assets-eu.researchsquare.com/files/rs-8002151/v1/6767494283b4f2ea9c2f6093.png"},{"id":96824950,"identity":"3546077b-8bf0-4b88-ba80-577155ecb58b","added_by":"auto","created_at":"2025-11-26 12:39:06","extension":"png","order_by":11,"title":"Figure 11","display":"","copyAsset":false,"role":"figure","size":408779,"visible":true,"origin":"","legend":"\u003cp\u003eFlexural sample geometric accuracy analysis: a) photo of the flexural sample, b) 3D scanned point cloud data, and c) point cloud comparison results.\u003c/p\u003e","description":"","filename":"Picture11.png","url":"https://assets-eu.researchsquare.com/files/rs-8002151/v1/acbb792261299fa70104b9d9.png"},{"id":96824972,"identity":"5e5115c2-9be8-496c-a61b-6fabcee8d532","added_by":"auto","created_at":"2025-11-26 12:39:07","extension":"png","order_by":12,"title":"Figure 12","display":"","copyAsset":false,"role":"figure","size":630792,"visible":true,"origin":"","legend":"\u003cp\u003eFailure modes observed of samples under testing: a) tensile test, and b) flexural test.\u003c/p\u003e","description":"","filename":"Picture12.png","url":"https://assets-eu.researchsquare.com/files/rs-8002151/v1/cb4d04846f3235dd67c375dc.png"},{"id":103765648,"identity":"d5d447f3-1738-435a-88b7-c05e4a6410e4","added_by":"auto","created_at":"2026-03-02 16:06:33","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":3789453,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-8002151/v1/29d15c6c-d577-481a-9a54-d4b5d72cc542.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Wedged Mortise-Tenon Structure for Fixed Connections in Additive Manufacturing Assemblies Using Fused Filament Fabrication","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eAdditive manufacturing (AM), rapid prototyping or 3D printing, has transformed the manufacturing landscape by enabling the fabrication of geometrically intricate components with reduced material waste(Brahma et al., \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e2025\u003c/span\u003e; Shen, Zhang, et al., \u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e2025\u003c/span\u003e). Among the various Additive Manufacturing techniques, FFF stands out due to its accessibility and cost-effectiveness. However, the layer-by-layer deposition process characteristic of FFF introduces several challenges, including anisotropy, surface roughness, and dimensional inaccuracies (Crockete \u003cem\u003eet al.\u003c/em\u003e, n.d.; Gibson et al., \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e2021\u003c/span\u003e; Thompson et al., \u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e2016\u003c/span\u003e; Xu et al., \u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e2025\u003c/span\u003e). These inherent limitations significantly impact assembly design, particularly for fixed connections that rely on precise geometry and material properties.\u003c/p\u003e\u003cp\u003eAssembly plays a fundamental role in manufacturing, facilitating the creation of complex systems through the integration of discrete components. Over the course of industrial development, a diverse range of fixed connection methods has been developed, including discrete fasteners (e.g., screws and rivets), adhesive bonding, and interlocking mechanisms (Oh et al., \u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e2018\u003c/span\u003e). Among these, the mortise-tenon (M-T) joint has emerged as a cornerstone of traditional woodworking and mechanical engineering due to its ability to provide strong, durable, and aesthetically pleasing connections without the need for auxiliary hardware (Baptista et al., \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e2020\u003c/span\u003e; Hajdarevic et al., \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e2023\u003c/span\u003e; Li et al., \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e2020\u003c/span\u003e; Schlake et al., \u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e2025\u003c/span\u003e). Its inherent simplicity and adaptability have rendered it a preferred choice in various applications, from furniture making to architectural frameworks. Despite its historical significance and widespread utility, the potential applications of M-T joints in Additive Manufacturing remain underexplored.\u003c/p\u003e\u003cp\u003eThe effective connection of parts is crucial for assembly design, influencing both performance and manufacturability. Traditionally, Design for Assembly (DFA) principles guide the choice of connection methods to minimize assembly time and cost while ensuring structural integrity and functionality (Kuo et al., \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e2001\u003c/span\u003e; Tuvayanond and Prasittisopin, \u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e2023\u003c/span\u003e; Wang et al., \u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e2021\u003c/span\u003e; Zha et al., \u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e2001\u003c/span\u003e). Conventional methods include discrete fasteners, adhesives, energy bonding, and integral fits, each with specific application requirements and challenges. Discrete fasteners offer modularity and disassembly but increase costs and complexity. Adhesive bonding distributes stress uniformly and eliminates visible connectors but is limited by curing requirements and environmental factors. Energy bonding provides high-strength joints but requires specialized equipment and is constrained by material properties. Integral fits streamline assembly by integrating connection features into part designs, reducing assembly time and hardware needs, though they depend on precision manufacturing and material compatibility (Chaves et al., \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e2018\u003c/span\u003e; Cowley \u003cem\u003eet al.\u003c/em\u003e, n.d.; Delzendehrooy et al., \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e2022\u003c/span\u003e; Lambiase et al., \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e2021\u003c/span\u003e; Maggiore et al., \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e2021\u003c/span\u003e; Mehta, \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e2017\u003c/span\u003e; Song, \u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e2022\u003c/span\u003e). The rise of Additive Manufacturing introduces new opportunities and challenges, as AM\u0026rsquo;s ability to create complex geometries and layer materials with high precision demands a reevaluation and adaptation of traditional connection techniques to this new manufacturing paradigm (Liu et al., \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e2023\u003c/span\u003e; Mechter et al., \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e2022\u003c/span\u003e; Srivastava and Rathee, \u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e2022\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eThe use of adhesives in Additive Manufacturing has been extensively studied to address the limitations of mechanical connections and enhance the structural integrity of AM printed parts (Khosravani et al., \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e2023\u003c/span\u003e; Pradel et al., \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e2018\u003c/span\u003e; Wei et al., \u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e2024\u003c/span\u003e). Golewski, Sadowski, and Nowicki highlighted the advantages of using 3M\u0026trade; VHB\u0026trade; 5925 double-sided adhesive tape for bonding additively manufactured AM polymer adherends, noting its ability to preserve structural integrity, conform to rough surfaces, simplify the joining of complex geometries, and distribute loads evenly. However, they also identified limitations such as insufficient shear strength for high-load applications and the viscoelastic nature of adhesives, which can impair joint longevity (Golewski et al., \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). Similarly, Garcia and Prabhakar demonstrated that deposited adhesive layers could significantly enhance bond strength and stiffness in single-lap joints, although the effectiveness depended on proper surface preparation and material compatibility (Garcia and Prabhakar, \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e2017\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eThe integration of effective joining methods in AM process is crucial for enhancing the structural integrity and functionality of AM components. The challenges in joining dissimilar fabricated parts and the limitations of conventional techniques for complex geometries have led researchers to explore new joining methods. Mechanical fasteners for AM printed parts are an emerging technique with distinct advantages and limitations. Unlike adhesive joining, mechanical fastening requires no surface preparation and allows for easy inspection and disassembly, except in the case of rivets. Additionally, mechanical fastening avoids thermal degradation issues associated with excessive heating in other joining methods. However, mechanical fasteners increase component weight and induce stress around the fastener holes, which can reduce strength and lead to corrosion. The process can also be labor-intensive, involving additional fixtures and stages such as heating and inserting fasteners, which may damage and weaken the surrounding structure. Despite its simplicity, there is limited research on joining AM parts using mechanical fasteners. Hybrid joints combining mechanical fasteners and adhesives have not yet been extensively studied or reported. Fahreddin Fatih \u0026Ouml;ng\u0026uuml;l, İlyas Kandemir, and Esma Pala \u0026Ouml;ng\u0026uuml;l conducted a study on adhesive and glue applications in Additive Manufacturing implements, specifically focusing on fasteners within the Fused Deposition Modeling (FDM). They investigated common fastener methods for FDM-manufactured parts, identifying factors influencing tensile and bending strengths using various design techniques and infill ratios, with Polylactic Acid (PLA) as the primary material. The study examined four fastening methods, including heat-set inserts and embedded square nuts, to enhance structural integrity and optimize assembly methodologies. Test samples with different infill ratios were designed to comprehensively test tensile, flexural, and tightening torque strengths. Findings revealed that the adhesion strength of heat-set inserts is significantly influenced by infill ratio, while embedded nut methods showed varying load responses, highlighting the importance of wall thickness. Despite advancements, the study acknowledged limitations of conventional adhesives in FDM, such as lower mechanical strength of plastics compared to metals and reduced strength due to surface roughness from the layer-by-layer nature of FDM. The research emphasizes the need for innovative materials and techniques to improve adhesive applications for high-stress applications. These insights advance understanding of adhesive applications in FDM and pave the way for optimized fastening techniques in specialized fields like aerospace and medical industries, highlighting the necessity for tailored solutions considering mechanical properties, production efficiency, and practical application needs (\u0026Ouml;ng\u0026uuml;l et al., \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e2024\u003c/span\u003e; Zhang et al., \u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e2022\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eThe exploration of M-T joints in Additive Manufacturing is particularly relevant to industries requiring lightweight, modular, and disassemblable structures. For example, in aerospace and automotive sectors, components often demand high strength-to-weight ratios and ease of assembly without adhesives or metal fasteners, which add weight and complexity. Similarly, in furniture design, M-T joints enable glue-free assembly of AM fabricated parts, aligning with sustainability goals by simplifying recycling and reducing material waste. Medical device manufacturing also benefits from such joints, where biocompatible materials like PLA can form sterilizable, snap-fit connections for prosthetics or surgical tools. These applications underscore the need for robust, printable joints that bypass traditional joining limitations while leveraging AM\u0026rsquo;s geometric flexibility. The advancement of Additive Manufacturing has revolutionized the design and assembly of complex structures, necessitating innovative connection and joining methods. Traditional techniques such as discrete fasteners, adhesive bonding, energy bonding, and integral fits have been foundational, but AM introduces new opportunities and challenges. Luo et al. developed the Chopper framework, which uses Binary Space Partitioning (BSP) trees to segment objects into smaller parts, ensuring effective alignment and interconnection through well-designed connectors (Luo et al., \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e2012\u003c/span\u003e). Song et al. introduced a voxelization-based method for creating interlocking 3D parts from complex shapes, facilitating robust connections through the development of connection graphs (Song et al., \u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e2015\u003c/span\u003e). Xin et al. focused on generating multi-knot burr puzzles, employing a knot network framework and a greedy algorithm to construct intricate assemblies of interlocking pieces (Xin et al., \u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e2011\u003c/span\u003e). Despite the advancements, challenges remain, such as optimizing for multiple conflicting goals, translating complex geometries into effective interlocking features, and achieving non-orthogonal connections. These studies highlight the critical balance between structural integrity and design complexity in generating functional AM assemblies. Interlocking mechanisms excel in AM environments because they eliminate the need for additional hardware or adhesives, reduce assembly time, and exploit the geometric complexity achievable. However, they require careful design consideration to ensure structural integrity and ease of assembly/disassembly.\u003c/p\u003e\u003cp\u003eThese traditional and emerging methods highlight the diverse approaches available for assembling AM fabrciated parts (see Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). By leveraging these techniques, designers can address the specific challenges posed by Additive Manufacturing processes, paving the way for more efficient and functional assemblies. The integration of interlocking designs, such as M-T joints, represents a promising avenue for enhancing fixed connections, combining strength, simplicity, and the unique design opportunities of Additive Manufacturing. The M-T joint, a centuries-old design, traditionally consists of a protruding tenon inserted into a corresponding mortise, forming a secure interlocking connection without external fasteners. This simplicity aligns with the goals of Additive Manufacturing to minimize material use and auxiliary components, making it an ideal candidate for exploration within the domain of FFF. The adaptability of M-T joints allows for customization to meet specific load-bearing and aesthetic requirements. This adaptability is further amplified by the geometric freedom inherent in AM, enabling the design of advanced features such as dovetail joints, cylindrical tenons, and reinforced mortises to optimize stress distribution and mechanical performance.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eHowever, adapting M-T joints for FFF introduces several challenges. The success of such joints in traditional manufacturing depends heavily on precise machining and consistent material properties. In FFF, the layer-by-layer process introduces surface imperfections, dimensional deviations, and internal defects, all of which can compromise the fit and structural integrity of the joint. Additionally, the anisotropic mechanical properties of FFF-printed parts can lead to uneven load distribution, further complicating the performance of these joints. Addressing these challenges requires a comprehensive investigation into the design and optimization of M-T joints specifically tailored for FFF.\u003c/p\u003e\u003cp\u003eThis research aims to explore the feasibility and performance of wedged M-T joints as a fixed connection method in Additive Manufacturing, with a particular emphasis on FFF. The primary objectives are to develop optimized designs that address challenges such as mechanical performance, dimensional precision, and printability; evaluate the mechanical performance of these joints under various loading conditions, including tensile and flexural forces; and provide practical guidelines for their implementation in Additive Manufacturing assemblies, considering factors such as material selection, joint geometry, and printing parameters.\u003c/p\u003e\u003cp\u003eThis study introduces innovative M-T designs compatible with FFF technology, experimentally validating their mechanical properties and feasibility. Figure\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e illustrates the flow of this proposed work, highlighting the formulation of design and manufacturing guidelines for broader adoption. These guidelines specifically address the unique challenges posed by FFF while harnessing its capabilities effectively. By overcoming the limitations of the build volume associated with commercially available 3D printers, this research significantly enhances the applicability and efficiency of AM process across various industrial contexts.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eThe integration of these advancements aims to expand assembly design within Additive Manufacturing, paving the way for sustainable, efficient, and functional manufacturing solutions across diverse sectors, including furniture design, construction, automotive, and aerospace. By tackling the technical challenges inherent to FFF and its build volume constraints, this study broadens the practical applications of AM, positioning it as a more viable and efficient option for a wide range of industries.\u003c/p\u003e"},{"header":"2. Design and Methodology","content":"\u003cp\u003eThe design of M-T joints for FFF was developed with a primary focus on optimizing geometric parameters to achieve superior mechanical performance. These objectives were carefully balanced against the unique constraints of FFF processes, such as anisotropy in material properties, the layer-by-layer fabrication method, and the need for efficient material and time usage. The key considerations driving the design included maximizing joint strength, ensuring ease of manufacturability, and minimizing the use of support material to improve overall printability and reduce post-processing requirements.\u003c/p\u003e\u003cp\u003eDrawing inspiration from traditional woodworking, the overall design adopts a wedged M-T structure, which provides enhanced mechanical interlocking through its self-locking capabilities under load. The wedged tenon, a hallmark of woodworking joints, was adapted for FFF by incorporating a kerf, or slit, into the tenon. This kerf allows for controlled deformation during assembly, enabling a tighter fit without inducing excessive stress on the joint or surrounding material. Additionally, the mortise incorporates a relief zone specifically designed to facilitate the slight deformation of the tenon structure. This deformation allows the tenon to interlock securely with the mortise through an interference fit, ensuring a robust and stable connection.\u003c/p\u003e\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\u003ch2\u003e2.1 Mortise-Tenon Joint Design for FFF\u003c/h2\u003e\u003cp\u003eThe geometry of the tenon in the wedged M-T joint was carefully designed to enhance self-locking behavior, thereby improving load-bearing capacity and assembly stability without the need for additional fasteners or adhesives (Baleanu et al., \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2015\u003c/span\u003e). Key design parameters were considered, including the tenon width, length, thickness, and the angle of the mortise relief area, each of which plays a vital role in the mechanical performance and manufacturability of the joint (Abdelrahman et al., \u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e2017\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eAs shown in Fig.\u0026nbsp;3\u003cb\u003eError! Reference source not found.\u003c/b\u003e, the tenon width (W) influences the overall strength of the joint by determining the contact area between the tenon and mortise. A wider tenon generally increases the surface area for load distribution, improving the joint\u0026rsquo;s strength, but it must be optimized to balance material usage and printability. The tenon length (L) is another critical parameter that governs the joint\u0026rsquo;s resistance to pull-out forces. A longer tenon enhances the joint\u0026rsquo;s strength, particularly under tension, by increasing the surface area over which forces are distributed. However, excessively long tenons can lead to challenges during the assembly process and may reduce printability due to the complexity of the geometry. The tenon thickness (T) directly impacts the joint\u0026rsquo;s ability to resist compression and tension. A thicker tenon is more robust under load, but if it is too thick, it can increase the potential for material deformation and failure during printing, especially in FFF processes where the layer-by-layer deposition method can introduce weak interfaces between layers. The mortise relief area angle (θ) is another essential parameter that impacts the fit between the mortise and tenon. The relief area reduces stress concentration during assembly, facilitating a tighter fit and improving the overall strength of the joint. The angle of this relief zone must be optimized to ensure the joint\u0026rsquo;s performance under mechanical loading while accounting for the dimensional variations inherent in FFF fabrication.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eL9 orthogonal array for four geometric parameters at three levels.\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"6\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eRun\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eL [mm]\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eW [mm]\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eT [mm]\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u003cp\u003eθ [\u0026deg;]\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c6\"\u003e\u003cp\u003evon Mises [MPa]\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e8\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e7.5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e2.5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e10\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e3.35\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e8\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e10\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e3.75\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e12.5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e3.95\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e8\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e12.5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e15\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e2.95\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e4\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e10\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e7.5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e3.75\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e15\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e5.13\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e10\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e10\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e10\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e1.88\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e6\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e10\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e12.5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e2.5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e12.5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e3.21\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e7\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e12\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e7.5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e12.5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e3.14\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e8\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e12\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e10\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e2.5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e15\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e4.94\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e9\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e12\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e12.5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e3.75\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e10\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e2.92\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003eThe design parameters of the M-T joints\u0026mdash;width (W), length (L), thickness (T), and angle (θ)\u0026mdash; were systematically determined and optimized using an orthogonal array experimental design, a robust method for efficiently evaluating multiple factors with minimal experimental runs (Ranjit K. Roy, \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e2001\u003c/span\u003e). This approach is widely used in additive manufacturing studies to balance parameter interactions, optimize performance metrics (Chohan et al., \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e2022\u003c/span\u003e; Khalid and Peng, \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). The orthogonal array selected for this study, shown in Table\u0026nbsp;1\u003cb\u003eError! Reference source not found.\u003c/b\u003e, encompasses nine experimental runs, each representing a unique combination of the design parameters at three levels. The parameter levels were chosen to reflect practical constraints and achievable dimensions within the capabilities of FFF while covering a sufficient range to identify meaningful trends. The orthogonal array enables a systematic evaluation of the effects of each parameter and their interactions on the mechanical performance of the joint, including strength, stiffness, and toughness. Each joint configuration will be fabricated using the same FFF process parameters to ensure consistency across tests.\u003c/p\u003e\u003cp\u003eThe finite element simulations were conducted using a linear elastic material model for PLA, assuming isotropic behavior to simplify the analysis. The PLA material properties were defined based on preliminary tensile tests and literature values. The model employed 3D solid tetrahedral elements (C3D10) to accurately capture the complex geometry of the mortise-tenon joints. Boundary conditions were applied by fully constraining the base of the mortise component, while a displacement-controlled load was applied to the tenon end to simulate tensile loading.\u003c/p\u003e\u003cp\u003eTensile properties were initially evaluated through finite element simulation for each parameter configuration. The simulation results, shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ea, highlighted the regions of maximum stress concentration under tensile loading. Subsequent mechanical testing of the fabricated samples validated the simulation results. Images of the failure modes (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eb) confirmed that the areas of failure during physical testing corresponded precisely with the high-stress regions identified in the simulation. This agreement between simulation and experimental observations demonstrates the effectiveness of the orthogonal array approach for optimizing the design parameters and highlights the reliability of the simulation tools in predicting mechanical behavior.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eThe optimized design parameters (W\u0026thinsp;=\u0026thinsp;12 mm, L\u0026thinsp;=\u0026thinsp;7.5 mm, T\u0026thinsp;=\u0026thinsp;3.75 mm, and θ\u0026thinsp;=\u0026thinsp;15\u0026deg;) derived from simulation results (see Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e) are expected to maximize the mechanical performance of the M-T joint while addressing the inherent constraints of FFF, including the layer-by-layer fabrication process and potential geometric deviations. Figure\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e and Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e illustrate the finalized design for the tensile and flexural samples, which were subsequently fabricated and subjected to mechanical testing for both tensile and flexural properties, further validating the optimization process.\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eComparison of factors and levels to identify the optimized parameter combination.\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"6\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colspan=\"2\" morerows=\"1\" nameend=\"c2\" namest=\"c1\" rowspan=\"2\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colspan=\"4\" nameend=\"c6\" namest=\"c3\"\u003e\u003cp\u003eFactor\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eL [mm]\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eW [mm]\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003eT [mm]\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003eθ [\u0026deg;]\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\" morerows=\"2\" rowspan=\"3\"\u003e\u003cp\u003eLevel\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e3.42\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e3.87\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e3.83\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e2.72\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e3.41\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e3.59\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e4.00\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e3.44\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e3\u003c/p\u003e\u003cp\u003e4\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e3.67\u003c/p\u003e\u003cp\u003e12\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e3.03\u003c/p\u003e\u003cp\u003e7.5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e2.66\u003c/p\u003e\u003cp\u003e3.75\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e4.341\u003c/p\u003e\u003cp\u003e15\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec4\" class=\"Section2\"\u003e\u003ch2\u003e2.2 Material Selection and Printing Parameters\u003c/h2\u003e\u003cp\u003eThe selection of materials is critical in determining the performance of the M-T joints. Preliminary tensile tests were conducted on samples printed using three commonly used FFF materials: ABS, PLA, and PETG. The tests carried out at a speed of 6 mm/min, revealed notable differences in tensile strength: PETG exhibited the highest tensile strength at 273 MPa, followed by PLA at 253 MPa and ABS at 107 MPa. Despite PETG\u0026rsquo;s superior tensile strength, PLA was chosen for the joint design due to its comparable strength, better printability, lower warping tendency, and ease of use in various printing conditions. PLA\u0026rsquo;s suitability is further supported by its widespread adoption in FFF research and industrial applications, where it balances stiffness and tensile strength comparable to engineering-grade polymers, making it ideal for structural joints(Gibson et al., \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). Its low warping tendency and minimal shrinkage ensure dimensional stability, critical for precise interference fits in M-T joints (Alzyod and Ficzere, \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2023\u003c/span\u003e; Shen et al., \u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e2025\u003c/span\u003e). Environmentally, PLA\u0026rsquo;s biodegradability aligns with sustainable manufacturing goals, as emphasized in lifecycle assessments of AM materials (Rezvani Ghomi et al., \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). In addition to tensile strength, ductility and toughness were evaluated based on elongation at break and energy absorption during tensile testing. PETG exhibited the highest elongation at break (12.4%), followed by ABS (8.7%) and PLA (4.3%), confirming its superior ductility. Toughness, estimated from the area under the stress-strain curve, also followed this trend. However, PETG was less favorable due to its complex printing characteristics and tendency to warp. ABS demonstrated moderate toughness and better thermal resistance but suffered from layer adhesion issues. PLA, while less ductile, provided the best dimensional stability and print consistency, making it the most suitable choice for the M-T joint application.\u003c/p\u003e\u003cp\u003eFigure \u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e compares the tensile strength performance of ABS, PLA, and PETG, providing a clear illustration of the material properties that influenced the selection process. These material properties\u0026mdash;along with optimized printing parameters\u0026mdash;were crucial factors in ensuring that the M-T joints would perform reliably under expected loading conditions while maintaining manufacturability in an FFF process.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eThe performance of the M-T joints was influenced by the selection of key printing parameters, which were carefully optimized to balance joint strength and manufacturing feasibility. The prints were produced using the Original Prusa MK4S with a 0.4 mm nozzle, ensuring precision and reliability. These parameters ensured consistent mechanical properties, material efficiency, and ease of production within the constraints of FFF technology. A finer layer height and appropriate infill density contributed to smooth layer bonding and adequate internal structure, while standard extrusion settings for PLA maintained optimal material flow and adhesion. Preliminary testing confirmed that tensile speed had minimal influence on joint strength, validating the sufficiency of these standard settings for achieving high-quality prints. Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e summarizes the printing parameters used for all sample preparations.\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003ePrinting parameters for all sample preparation with PLA.\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"2\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eParameter\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eValue\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eNozzle temperature [\u0026deg;C]\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e210 (215 for first layer)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eBed temperature [\u0026deg;C]\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e60\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eLayer height [mm]\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0.10 (0.15 for first layer)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eInfill pattern [-]\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eRectilinear\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eInfill density [%]\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e20\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec5\" class=\"Section2\"\u003e\u003ch2\u003e2.3 Testing Procedures\u003c/h2\u003e\u003cp\u003eMechanical Testing: All mechanical tests were conducted in accordance with relevant ASTM standards. Tensile and 3-point flexural tests were conducted to assess joint strength and stiffness. For tensile test, specimen is gripped firmly by each end of the testing machine and aligned so that there would not be bending forces during the test. For flexural test, specimen is placed on two parallel supports at a distance apart, the load would be applied at the center between the supports. Load would be increased until the specimen fractures in both tests. To examine the influence of testing speed on tensile performance, initial tests (see Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e) were conducted at speeds of 6 mm/min, 30 mm/min, and 60 mm/min. The results showed no significant differences in joint performance across these speeds, confirming that testing speed had a negligible effect on strength. Based on these findings, a speed of 60 mm/min was selected for tensile testing. The flexural tests simulated real-world bending forces and were conducted at a speed of 10 mm/min with a span length of 3 inches to measure joint stiffness and bending resistance effectively. For comparison, all mechanically tested samples were evaluated against adhesive-bonded samples prepared using SUPER GLUE Instant Adhesive, which has a reported tensile strength of 17.2 Mpa (2500 psi) according to its datasheet. These adhesive-bonded samples were cured for at least 24 hours prior to testing, ensuring reliable baseline performance for comparison with the M-T joints. During tensile testing, the mortise and tenon components were aligned such that the applied load acted axially along the length of the tenon, simulating a direct pull-out scenario. This ensured that the joint experienced pure tensile stress without bending. For flexural testing, the assembled joint was positioned horizontally with the tenon spanning across the supports and the mortise located centrally under the loading nose, allowing the joint to experience bending stress perpendicular to the tenon axis. This setup was designed to evaluate the joint\u0026rsquo;s resistance to shear and bending forces under realistic loading conditions.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eDimensional Accuracy: Dimensional accuracy was evaluated using the Revopoint POP2 3D scanner, featuring a resolution of 0.015 mm, to ensure the printed joints met required tolerances and assembly precision. Flexural test samples were chosen for scanning due to their larger surface area, which amplifies the impact of any discrepancies on the overall Cloud-to-Mesh (C2M) distance analysis. For each sample, the top, bottom, and two side surfaces were scanned to provide comprehensive geometric coverage. The scanned point cloud data was processed and reconstructed using Revo Studio, ensuring high-quality and accurate representations of the sample geometries. The C2M distance analysis was conducted with CloudCompare v2.12.4, which allowed for precise comparisons between the reconstructed point clouds and the nominal CAD mesh models.\u003c/p\u003e\u003c/div\u003e"},{"header":"3. Results and Discussion","content":"\u003cdiv id=\"Sec7\" class=\"Section2\"\u003e\u003ch2\u003e3.1 Mechanical Performance Analysis\u003c/h2\u003e\u003cp\u003eThe mechanical performance of the M-T (M-T) joints was evaluated through tensile and flexural testing to provide a comprehensive assessment of their strength, stiffness, and toughness in comparison to glued joints. These tests also served to examine the influence of the joint geometry and FFF parameters on mechanical behavior. The standard deviations for all mechanical properties were estimated using the Student\u0026rsquo;s t-distribution due to the limited sample size, ensuring statistical robustness.\u003c/p\u003e\u003cp\u003e\u003cem\u003eTensile Testing\u003c/em\u003e\u003c/p\u003e\u003cp\u003eTensile tests were conducted to compare the load-bearing capacity and failure modes of glued and M-T joints under uniaxial loading. Table\u0026nbsp;\u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e4\u003c/span\u003e summarizes the results, and the mechanical properties are further illustrated in Fig.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003e.\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab4\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 4\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eTensile test results of adhesive and M-T joining, with standard deviation estimates using Student\u0026rsquo;s T-Distribution (95% confidence level).\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"7\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eStrength [Mpa]\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eStd. Dev. [\u0026plusmn;]\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eStiffness [N/mm]\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u003cp\u003eStd. Dev. [\u0026plusmn;]\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c6\"\u003e\u003cp\u003eToughness [J/cm3]\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c7\"\u003e\u003cp\u003eStd. Dev. [\u0026plusmn;]\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eAdhesive Joining\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e2.46\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e1.00\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e1033.25\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e176.47\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e69.19\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e\u003cp\u003e32.33\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eM-T Joining\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e5.16\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e0.66\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e146.08\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e16.10\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e4429.02\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e\u003cp\u003e556.33\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eThe M-T joints exhibited a tensile strength of 5.16\u0026thinsp;\u0026plusmn;\u0026thinsp;0.66 MPa, more than double that of the glued joints (2.46\u0026thinsp;\u0026plusmn;\u0026thinsp;1.00 MPa), as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003ea. The marked improvement can be attributed to the self-locking interlocking geometry of the M-T joints, which enables a more efficient transfer of tensile loads across the joint interface. In contrast, the glued joints depend on the adhesive\u0026rsquo;s shear strength, which becomes a limiting factor under tensile loading. The relatively small standard deviation for the M-T joints indicates consistent manufacturing quality and performance, whereas the higher variability observed for the glued joints suggests potential inconsistencies in adhesive application or bonding quality. These findings reinforce the reliability of the M-T design over traditional adhesive joints in tensile loading scenarios.\u003c/p\u003e\u003cp\u003eIn Fig.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003eb, the glued joints demonstrated a significantly higher tensile stiffness of 1033.25\u0026thinsp;\u0026plusmn;\u0026thinsp;176.47 N/mm compared to 146.08\u0026thinsp;\u0026plusmn;\u0026thinsp;16.10 N/mm for the M-T joints. This discrepancy highlights a trade-off inherent in the M-T design: while the glued joints provide rigidity, the M-T joints allow for controlled deformation, which can be beneficial in applications requiring flexibility or energy dissipation. The lower stiffness of the M-T joints could also be linked to the inherent anisotropy of FFF parts, particularly in layer bonding and the kerf slit design. Although this reduced stiffness may seem disadvantageous for static load-bearing applications, it enhances the joints\u0026rsquo; toughness, as discussed below.\u003c/p\u003e\u003cp\u003eThe M-T joints outperformed the glued joints significantly in tensile toughness as depicted in Fig.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003ec, achieving 4429.02\u0026thinsp;\u0026plusmn;\u0026thinsp;556.33 J/cm\u0026sup3; compared to the glued joints\u0026rsquo; 69.19\u0026thinsp;\u0026plusmn;\u0026thinsp;32.33 J/cm\u0026sup3;. The high toughness reflects the M-T joints\u0026rsquo; ability to absorb and dissipate energy, making them highly suitable for dynamic or impact loading conditions. This behavior is attributed to the joint\u0026rsquo;s ability to distribute stresses more evenly, reducing the likelihood of brittle failure observed in glued samples. The toughness advantage of M-T joints aligns with their observed failure modes. The M-T joints primarily failed through gradual layer delamination, providing a warning before ultimate failure, whereas the glued joints exhibited sudden adhesive failure, which is less desirable in practical applications.\u003c/p\u003e\u003cp\u003e\u003cem\u003eFlexural Testing\u003c/em\u003e\u003c/p\u003e\u003cp\u003eFlexural tests were conducted to evaluate the bending performance of M-T joints compared to glued joints. The properties measured include flexural strength, modulus, toughness, and strain at failure. The results, summarized in Table\u0026nbsp;\u003cspan refid=\"Tab5\" class=\"InternalRef\"\u003e5\u003c/span\u003e and depicted in Fig.\u0026nbsp;\u003cspan refid=\"Fig10\" class=\"InternalRef\"\u003e10\u003c/span\u003e, reveal significant differences in the mechanical response of the two joint types, reflecting the distinct mechanisms through which they resist bending loads.\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab5\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 5\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eFlexural test results of adhesive and M-T joining, with standard deviation estimates using Student\u0026rsquo;s T-Distribution (95% confidence level).\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"9\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c9\" colnum=\"9\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eFlexural Strength [Mpa]\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eStd. Dev. [\u0026plusmn;]\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eFlexural Modulus[MPa]\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u003cp\u003eStd. Dev. [\u0026plusmn;]\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c6\"\u003e\u003cp\u003eFlexural Strain [-]\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c7\"\u003e\u003cp\u003eStd. Dev. [\u0026plusmn;]\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c8\"\u003e\u003cp\u003eToughness\u003c/p\u003e\u003cp\u003e[J/cm\u003csup\u003e3\u003c/sup\u003e]\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c9\"\u003e\u003cp\u003eStd. Dev. [\u0026plusmn;]\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eAdhesive Joining\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e5.157\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e1.408\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e374.64\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e80.37\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e0.012\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e\u003cp\u003e0.003\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e\u003cp\u003e103.81\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c9\"\u003e\u003cp\u003e54.44\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eM-T Joining\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e8.126\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e0.370\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e222.18\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e12.40\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e0.050\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e\u003cp\u003e0.010\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e\u003cp\u003e945.10\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c9\"\u003e\u003cp\u003e190.68\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003eThe M-T joints achieved a flexural strength of 8.126\u0026thinsp;\u0026plusmn;\u0026thinsp;0.370 MPa, outperforming the glued joints, which reached only 5.157\u0026thinsp;\u0026plusmn;\u0026thinsp;1.408 MPa. This represents a 57.5% increase in bending strength for the M-T joints. The lower variability in the M-T samples (standard deviation of 0.370 MPa) compared to the glued joints (1.408 MPa) suggests that the interlocking design of the M-T joints enhances repeatability and reliability. The superior strength of the M-T joints can be attributed to the wedged interlocking mechanism, which effectively distributes bending stresses along the joint interface. In glued joints, failure is localized at the adhesive bond, where stress concentration leads to abrupt failure, whereas the M-T design facilitates progressive load sharing across the tenon and mortise.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eThe glued joints exhibited a flexural modulus of 374.641\u0026thinsp;\u0026plusmn;\u0026thinsp;80.373 MPa, significantly higher than the M-T joints\u0026rsquo; 222.181\u0026thinsp;\u0026plusmn;\u0026thinsp;12.400 MPa, indicating that glued joints are stiffer under bending loads. However, the higher stiffness of the glued joints comes at the expense of energy absorption capacity, as discussed below. The reduced modulus of the M-T joints suggests greater flexibility, enabling them to deform more under bending stresses without immediate failure. This characteristic is particularly advantageous for applications requiring joints to withstand dynamic or repetitive loading, as it allows the M-T joints to accommodate minor displacements without significant loss of structural integrity.\u003c/p\u003e\u003cp\u003eThe toughness, representing the energy absorbed during bending, was substantially higher in the M-T joints (945.103\u0026thinsp;\u0026plusmn;\u0026thinsp;190.680 J/cm\u0026sup3;) than in the glued joints (103.813\u0026thinsp;\u0026plusmn;\u0026thinsp;54.441 J/cm\u0026sup3;). This indicates that the M-T joints absorbed 811% more energy before failure compared to the glued joints. The exceptional toughness of the M-T joints reflects their ability to undergo controlled deformation before failure. Observations during testing revealed gradual delamination and bending of the tenon in the M-T samples, which allowed them to sustain higher loads for longer durations. In contrast, the glued joints exhibited brittle failure, with abrupt adhesive bond separation leading to a catastrophic drop in load-bearing capacity.\u003c/p\u003e\u003cp\u003eThe maximum flexural strain for the M-T joints was 0.05\u0026thinsp;\u0026plusmn;\u0026thinsp;0.01, significantly higher than the glued joints\u0026rsquo; 0.012\u0026thinsp;\u0026plusmn;\u0026thinsp;0.003. This represents a 316% increase in strain capacity, emphasizing the ductility of the M-T joints. The ability to accommodate greater strain without failure highlights the robustness of the M-T joints under bending stresses. The wedged design and relief zones likely contribute to this behavior by mitigating stress concentrations and allowing for controlled deformation. Conversely, the limited strain capacity of the glued joints is indicative of their brittle failure mechanism, where bond failure occurs at relatively small displacements.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e\u003ch2\u003e3.2 Geometric Accuracy\u003c/h2\u003e\u003cp\u003eTo evaluate the alignment and assembly accuracy of the M-T joints, the assembled surfaces were scanned using a high-resolution Revopoint POP2 3D scanner, and the resulting point cloud data was processed in CloudCompare v2.12.4. The C2M distance method(Lague et al., \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e2013\u003c/span\u003e) was employed to quantify geometric discrepancies by comparing the scanned assembly surfaces (target) to the nominal CAD surfaces (reference). The C2M analysis generated a distance map, highlighting deviations at each point on the reference surface and producing an average distance metric that quantified the overall alignment error. For this study, the average C2M distance was 0.026\u0026thinsp;\u0026plusmn;\u0026thinsp;0.006 mm for the top and bottom surfaces and 0.025\u0026thinsp;\u0026plusmn;\u0026thinsp;0.008 mm for the side faces, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig11\" class=\"InternalRef\"\u003e11\u003c/span\u003e.\u003c/p\u003e\u003cp\u003eThese results demonstrate a high degree of alignment precision, especially considering the limitations inherent to the FFF printing process, such as a nozzle diameter of 0.4 mm and a layer thickness of 0.1 mm. The observed alignment accuracy, well within the expected tolerance limits for FFF, underscores the effectiveness of the M-T design and the manufacturing parameters in achieving accurate fits. This precision is critical to ensuring both the mechanical performance and structural integrity of the assembled joints.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec9\" class=\"Section2\"\u003e\u003ch2\u003e3.3 Discussion\u003c/h2\u003e\u003cp\u003eThe mechanical testing results highlight significant performance differences between M-T joints and glued joints, showcasing the advantages of the M-T design in both tensile and flexural loading scenarios. Tensile tests indicate that M-T joints possess superior load-bearing capacity and energy absorption compared to their glued counterparts. Although glued joints may demonstrate greater stiffness, their brittleness hinders toughness, resulting in sudden failure when the adhesive bond is compromised. Conversely, M-T joints utilize their interlocking geometry to effectively distribute stresses, leading to controlled and progressive failure modes. This property makes them particularly suitable for applications where strength and reliability are crucial.\u003c/p\u003e\u003cp\u003eFlexural testing further supports these findings, revealing that M-T joints can endure higher bending loads and greater deformations before failure. While glued joints exhibit higher stiffness, they lack the strain capacity and toughness that M-T joints provide. The wedged interlocking design of the M-T joints enhances stress distribution under bending forces, decreasing the likelihood of sudden failure and enabling greater energy absorption.\u003c/p\u003e\u003cp\u003eAnalyzing the failure modes (see Fig.\u0026nbsp;\u003cspan refid=\"Fig12\" class=\"InternalRef\"\u003e12\u003c/span\u003e) offers additional insights into these mechanical behaviors. Observations of M-T joint failures reveal a combination of delamination and material deformation in both tensile and flexural tests, indicative of a progressive and controlled failure mechanism. In contrast, glued joints primarily fail at the adhesive interface, resulting in sudden and catastrophic breakdowns. These contrasting failure patterns highlight the improved reliability and safety of the M-T design, which is better equipped to withstand dynamic or high-strain loading conditions.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eThe surface comparison results further show that the M-T joints achieved notable dimensional accuracy, with average C2M distances of 0.026 mm for the top and bottom surfaces and 0.025 mm for the side faces\u0026mdash;values that are well within the expected tolerance for FFF printing using a 0.4 mm nozzle and a 0.1 mm layer height. This suggests that the selected printing parameters, including layer height and infill density, effectively minimized distortions and ensured precise alignment. The small average C2M distances indicate a snug fit between the mortise and tenon components, which is critical for load distribution and overall joint strength. These results confirm the feasibility of employing FFF for creating mechanically reliable assemblies, as minimal misalignment reduces the risk of stress concentrations that could jeopardize performance. While the achieved accuracy is encouraging, minor surface irregularities typical of FFF printing may still impact assembly quality. Future studies could investigate additional process optimizations to further enhance dimensional precision.\u003c/p\u003e\u003cp\u003eIn summary, these findings demonstrate that M-T joints are a mechanically superior alternative to glued joints, especially in applications requiring strength, toughness, and controlled failure behavior. The results lay a strong groundwork for future investigations into M-T joint designs, including potential optimizations and material modifications, aimed at expanding their applicability in Additive Manufacturing and structural systems. Furthermore, the comparison of point clouds affirms that, with the right optimizations, FFF printing can yield precise and structurally robust mechanical joints.\u003c/p\u003e\u003c/div\u003e"},{"header":"4. Conclusion and Future Work","content":"\u003cp\u003eThis research has successfully demonstrated the viability and effectiveness of M-T joints as a fixed connection method in FFF, offering a robust alternative to traditional joining methods such as adhesive bonding and mechanical fasteners. The study directly addresses the critical challenges of overcoming build volume limitations and enhancing AM\u0026rsquo;s industrial applicability, while providing designers with an additional option for creating reliable assemblies in Additive Manufacturing. Through systematic optimization of joint geometry and careful consideration of FFF-specific constraints, the M-T design offers a balance of strength, precision, and manufacturability that makes it particularly well-suited for applications requiring both structural integrity and ease of assembly.\u003c/p\u003e\u003cp\u003eMechanical testing demonstrated the superior performance of M-T joints compared to traditional glued joints. M-T joints exhibited a tensile strength of 5.16\u0026thinsp;\u0026plusmn;\u0026thinsp;0.66 MPa, more than double that of glued joints (2.46\u0026thinsp;\u0026plusmn;\u0026thinsp;1.00 MPa). While glued joints showed higher tensile stiffness (1033.25\u0026thinsp;\u0026plusmn;\u0026thinsp;176.47 N/mm vs 146.08\u0026thinsp;\u0026plusmn;\u0026thinsp;16.10 N/mm), M-T joints demonstrated superior toughness and more controlled failure modes, making them more reliable for structural applications. The interlocking geometry effectively distributed stresses, resulting in progressive failure through delamination and material deformation rather than the sudden catastrophic failures observed in glued joints. Besides, alte\u003c/p\u003e\u003cp\u003ernative build orientations could significantly influence the mechanical performance of the joints. Printing the joint horizontally (with the tenon axis aligned in the XY plane) would align the layer lines with the loading direction, potentially improving tensile strength due to stronger in-layer bonding. However, this may introduce dimensional inaccuracies or require more support material. Similarly, changing the load alignment to act along the layer lines could reduce strength due to weaker interlayer adhesion.\u003c/p\u003e\u003cp\u003eDimensional accuracy analysis using high-resolution 3D scanning and C2M comparison revealed excellent precision, with average deviations of 0.026 mm for top/bottom surfaces and 0.025 mm for side faces. These results, achieved using a 0.4 mm nozzle and 0.1 mm layer height, demonstrate the capability of FFF to produce precise mechanical joints when properly optimized. However, this study has limitations that warrant acknowledgment:\u003c/p\u003e\u003cp\u003e\u003cul\u003e\u003cli\u003e\u003cp\u003eThe focus on PLA material and specific printing parameters may not generalize to diverse industrial requirements.\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003eMechanical testing was limited in sample size and loading/environmental conditions, which could affect real-world applicability.\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003eThe resolution of 3D scanning equipment constrained dimensional accuracy assessments.\u003c/p\u003e\u003c/li\u003e\u003c/ul\u003e\u003c/p\u003e\u003cp\u003eFuture research should prioritize:\u003c/p\u003e\u003cp\u003e\u003cul\u003e\u003cli\u003e\u003cp\u003eDeveloping design guidelines tailored to industrial applications (e.g., aerospace, construction).\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003eIntegrating advanced post-processing techniques to enhance joint performance.\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003eExploring hybrid methods combining M-T joints with adhesives or fasteners.\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003eImproving quality control protocols for dimensional accuracy.\u003c/p\u003e\u003c/li\u003e\u003c/ul\u003e\u003c/p\u003e\u003cp\u003eThe practical implications of this work extend to several emerging fields. In sustainable architecture, M-T joints enable the assembly of large-scale AM fabricated structures (e.g., partitions, fa\u0026ccedil;ades) without adhesives, simplifying material recovery and reuse. For consumer electronics, printed casings with integrated M-T connectors could eliminate screws, reducing part count and assembly time. Additionally, the medical industry could adopt these joints for patient-specific devices, such as orthotic braces, where PLA\u0026rsquo;s biocompatibility and the joints\u0026rsquo; reconfigurability allow for customizable, hygienic solutions. By addressing the limitations of conventional joining methods in these domains, the study advances AM toward broader industrial adoption, ensuring that research outcomes translate into tangible societal and economic benefits. These findings advance Additive Manufacturing assembly methods by demonstrating the viability of M-T joints in FFF. Future research could build on this work by developing industry-specific design guidelines, integrating hybrid joining techniques, and refining quality control protocols to create more efficient, sustainable, and reliable solutions. The success of M-T joints in this study highlights their potential to address current limitations in AM technology, such as build volume constraints, and could enable more complex, large-scale manufacturing applications in sectors like aerospace and modular construction.\u003c/p\u003e"},{"header":"5. Data availability statement","content":"\u003cp\u003eData will be made available on request.\u003c/p\u003e"},{"header":"6. Disclosure statement","content":"\u003cp\u003eNo potential conflict of interest was reported by the author(s).\u003c/p\u003e"},{"header":"Declarations","content":"\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eWeijun Shen designed the structure and finished 70% of the experiment and testing. Pengyu Zhang finished the least part of the experiment. Weijun Shen and Pengyu Zhang wrote the main manuscript, all the figures, and tables. All the authors reviewed the manuscript.\u003c/p\u003e\u003ch2\u003eData Availability\u003c/h2\u003e\u003cp\u003eData will be made available on request.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eAbdelrahman M, Reutzel EW, Nassar AR, Starr TL (2017) Flaw detection in powder bed fusion using optical imaging, \u003cem\u003eAdditive Manufacturing\u003c/em\u003e, Elsevier, Vol. 15, pp. 1\u0026ndash;11. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1016/J.ADDMA.2017.02.001\u003c/span\u003e\u003cspan address=\"10.1016/J.ADDMA.2017.02.001\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eAlzyod H, Ficzere P (2023) Material-Dependent Effect of Common Printing Parameters on Residual Stress and Warpage Deformation in 3D Printing: A Comprehensive Finite Element Analysis Study, \u003cem\u003ePolymers\u003c/em\u003e. 15(13):2893. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.3390/polym15132893\u003c/span\u003e\u003cspan address=\"10.3390/polym15132893\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eBaleanu D, Uǧurlu Y, Inc M, Kilic B (2015) Improved (G\u0026rsquo;/G)-expansion method for the time-fractional biological population model and Cahn-Hilliard equation. 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Eng Appl Artif Intell 14(1):61\u0026ndash;75. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1016/S0952-1976(00)00060-9\u003c/span\u003e\u003cspan address=\"10.1016/S0952-1976(00)00060-9\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eZhang J, Van Hooreweder B, Ferraris E (2022) Fused Filament Fabrication on the Moon, \u003cem\u003eJOM\u003c/em\u003e, Springer, Vol. 74 No. 3, pp. 1111\u0026ndash;1119. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1007/S11837-021-05031-Z/FIGURES/5\u003c/span\u003e\u003cspan address=\"10.1007/S11837-021-05031-Z/FIGURES/5\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"wedged mortise-tenon, fused filament fabrication, joint design, design for additive manufacturing assembly","lastPublishedDoi":"10.21203/rs.3.rs-8002151/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8002151/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThis study investigates the feasibility and performance of wedged mortise\u0026ndash;tenon (M\u0026ndash;T) joints as fixed connection mechanisms for assemblies fabricated through fused filament fabrication (FFF). By integrating a traditional self-locking joint concept into additive manufacturing, this work aims to provide an alternative to adhesives and mechanical fasteners. This bridges the gap from fabrication to the next-step assembly. An L9 orthogonal experimental design was applied to optimize four geometric parameters of the M\u0026ndash;T joint, and the resulting configurations were evaluated through finite element simulation, tensile and flexural mechanical testing, and dimensional accuracy analysis using high-resolution 3D scanning. The optimized design achieved a tensile strength of 5.16\u0026thinsp;\u0026plusmn;\u0026thinsp;0.66 MPa and flexural strength of 8.13\u0026thinsp;\u0026plusmn;\u0026thinsp;0.37 MPa, outperforming adhesive-bonded joints in both strength and energy absorption. A dimensional deviation of only 0.026 mm confirmed high printing precision and assembly quality. These results demonstrate that wedged M\u0026ndash;T joints offer reliable, strong, and sustainable fixed connections suitable for applications in furniture, automotive, aerospace, and medical device manufacturing.\u003c/p\u003e","manuscriptTitle":"Wedged Mortise-Tenon Structure for Fixed Connections in Additive Manufacturing Assemblies Using Fused Filament Fabrication","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-11-26 12:38:28","doi":"10.21203/rs.3.rs-8002151/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"4b2f7b16-a2e4-4dc9-b454-70c6cc06ce26","owner":[],"postedDate":"November 26th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2026-03-02T16:03:38+00:00","versionOfRecord":{"articleIdentity":"rs-8002151","link":"https://doi.org/10.1007/s40964-026-01565-3","journal":{"identity":"progress-in-additive-manufacturing","isVorOnly":false,"title":"Progress in Additive Manufacturing"},"publishedOn":"2026-02-24 15:57:59","publishedOnDateReadable":"February 24th, 2026"},"versionCreatedAt":"2025-11-26 12:38:28","video":"","vorDoi":"10.1007/s40964-026-01565-3","vorDoiUrl":"https://doi.org/10.1007/s40964-026-01565-3","workflowStages":[]},"version":"v1","identity":"rs-8002151","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-8002151","identity":"rs-8002151","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}