Advancing Strategies for Distortion Control in Megacasting: Critical Parameters and Compensation Techniques

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This disruptive approach offers potential benefits in terms of reduced part count, lower assembly cost, and improved structural performance. However, the process also introduces significant challenges in maintaining tight geometrical tolerances due to distortion caused by residual stresses and non-uniform cooling. This study advances strategies for minimizing distortion by combining insights from interviews, physical tests, and literature. Key process parameters, including tool compensation, quenching, and fixturing, are identified and analyzed. A balanced approach is proposed, integrating predictive tool compensation and fixturing during quenching to reduce distortion. The findings present a novel framework for controlling distortion while meeting both material and geometrical quality requirements in megacast components, paving the way for more sustainable and competitive manufacturing practices in the automotive industry. This paper represents one of the first structured efforts to integrate empirical shop-floor experience, existing literature, and early-stage testing to address distortion control in megacasting. Quality Assurance Casting Tolerances Distortion Figures Figure 1 Figure 2 Figure 3 Figure 4 1. Introduction The automotive industry's pursuit of lightweight and sustainable solutions has led to significant advancements in manufacturing technologies [ 1 ]. Among these, megacasting, also known as gigacasting, has emerged as a disruptive and transformative process, enabling the production of large, single-piece aluminum components that replace complex assemblies of up to hundreds of smaller parts. Cost savings in production are a primary driver [ 2 ]. Environmental impacts related to weight savings are also highlighted, but in this context the recycling of aluminum should be equally emphasized for its significant contribution to sustainability [ 3 ]. Tesla introduced the concept of megacasting and secured a patent for its shock-absorbing properties in crash scenarios in 2022 [ 4 ]. Megacasting has also been introduced as a competitive advantage by other brands, such as Mercedes-Benz, Volkswagen, Volvo Cars, and the Chinese brands Nio and Xpeng. Megacasting enables the production of large, single-piece castings that consolidate multiple components, reducing the need for assembly. This functional integration can lead to improved structural integrity and reduced manufacturing complexity. The larger mass and complexity of megacast components compared to traditional HPDC necessitate advanced thermal management to ensure uniform solidification and minimize defects like porosity or warping. However, the adoption of megacasting introduces challenges [ 5 ]. In this paper, the focus is on geometrical quality; the degree to which a manufactured component conforms to its intended shape and dimensions [ 6 ], ruled by tolerances. Ensuring high geometrical quality is critical for maintaining structural integrity, assembly precision, and overall vehicle quality and performance. Geometrical variation in components can propagate through subassemblies and affect the visual quality impressions related to flush and gaps in split lines of the produced vehicle. Large, thin-walled castings are especially sensitive to issues such as distortion, warping, and residual stresses due to the complex interplay of process parameters, such as variations in cooling rates across different areas or differences in section thickness. During solidification and cooling, the castings contract, interacting with constraints such as die walls. This interaction generates residual stresses, leading to complex spring back and continued warping during post-ejection cooling. In complex-shaped castings, non-uniform cooling conditions can cause plastic strain, resulting in permanent distortion [ 7 ]. Compared to traditional sheet metal assemblies, where hundreds of parts are joined together, megacasting significantly shortens the tolerance chain by eliminating the need for spot welding or other joining methods in numerous assembly stations in the production flow. However, this also removes the possibility of compensation steps, such as using lap joints in sheet metal assemblies, which allow for the joining of non-nominal parts while still meeting assembly requirements. As a result, ensuring the geometrical quality of megacast components becomes critical, as deviations cannot be corrected during an intermediate assembly stage. Addressing these challenges requires a comprehensive understanding of the factors influencing geometrical quality, including material properties, die design, quenching techniques, and trimming processes. 1.1. Scope of the paper This paper aims to explore the key parameters affecting geometrical quality in megacasting, drawing insights from literature, industry practices, and experimental tests. By identifying the root causes of variation and proposing strategies for improvement, this study contributes to the advancement of megacasting technologies, supporting the automotive industry's goals of achieving cost-efficient, sustainable, and high-quality vehicle components. In Section 2, the methodology is described. Section 3 focuses on the results from expert interviews and literature reviews. Section 4 describes the physical tests that have been performed, while Section 5 presents the results and discussion. Conclusions are found in Section 6. 2. Methodology The findings in this paper are based on a combination of three qualitative and experimental approaches. Insights were gathered through 12 semi-structured interviews with process engineers, designers, and quality assurance specialists from academia and industry, selected based on their extensive experience in high-pressure die casting (HPDC) and an interest in megacasting. These interviews offered valuable perspectives on the practical challenges and variability of key process parameters affecting geometrical quality, as well as new ideas for megacasting quality assurance. The interviews were recorded, transcribed, and systematically analyzed, providing critical knowledge about factors influencing geometrical quality and the challenges encountered in real-world applications. In parallel, a targeted review of relevant literature was carried out to map contributors to geometrical variation, focusing on aspects such as die design, quenching techniques, and material properties. The search employed keywords like “megacasting”, "geometrical variation", "dimensional variation", "distortions in HPDC components", "hyper-casting", "giga-press”, "shrinkage", "twisting" and "large casting" to identify relevant scientific sources. Additionally, a limited number of physical tests were performed in an industrial setting to investigate the effects of process parameters, including die temperature, quench media temperature, quench orientation, and quench time, on distortion in megacast components. 3. Factors Influencing Geometrical Quality in HPDC Megacasting is a form of HPDC, distinguished primarily by the sheer size of the components produced. Using Giga Presses capable of exerting clamping forces exceeding 9,000 tons, this process enables the creation of large, single-piece castings. However, the increased mass and geometric complexity introduce significant challenges—particularly in managing heat flow and solidification. More advanced thermal control, compared to traditional HPDC, is therefore critical to ensure uniform solidification and to reduce the risk of defects such as porosity, warping, and residual stresses. The casting process contains many steps, each of them providing its own challenges and contributors to geometrical variation in the produced megacast components. The main process steps are considered in this section, together with a discussion based on interviews and literature about the factors affecting geometrical quality. Some steps have been consolidated, or even excluded, to align with the objectives of this paper. Figure 1 introduces some terminology of a megacast component. Figure 2 illustrates the factors discussed in this section, where the letters i , l and t indicate the source of information (interviews ( i ), literature studies ( l ) or physical tests ( t )). Die-casting machine characteristics, such as die stiffness, maximum locking force and injection pressure are excluded from this discussion. Part geometry The design of the megacasted part geometry determines the foundation for geometrical quality by influencing cooling behavior, residual stresses, and distortions. Many requirements on function, cost and producibility must be met, but here the focus is on risk of distortion. The part's geometry significantly influences the risk of deviation from its nominal shape. Complex geometries , including large components, are more prone to amplifying residual stress development [ 8 ], increasing the likelihood of distortions and variations. Additionally, varying wall thicknesses can create uneven cooling rates, leading to residual stresses that result in distortions [ 9 , 10 ]. During the interviews, it was also mentioned that the cooling system can be used to compensate for the varying thickness. Incorporating draft angles into the design is beneficial from a geometry assurance perspective according to the interviewees. Draft angles help mitigate issues during ejection, as parts that shrink and adhere to the die may require increased ejection forces for release, potentially causing deformations [ 8 ]. Die and Material Die design plays a crucial role in the quality of high-pressure die cast components, as it directly impacts material flow, solidification, and cooling. The gating system , with its key features such as runners, ingates, and the biscuit (see Fig. 1 ) are carefully designed to ensure the molten metal fills the die cavity uniformly and without turbulence, minimizing defects like air entrapment or cold shuts. The runners guide the molten metal into the die, while the ingate controls the entry of metal into the cavity, balancing flow and pressure. The biscuit, located at the end of the shot sleeve, acts as a reservoir to maintain pressure during solidification, preventing shrinkage-related defects. Proper design of these features also helps optimize the thermal behavior of the casting and reduce residual stresses. Furthermore, the contraction of the gating system during solidification can drag the other sections of the casting causing distortion and hot tearing [ 11 ]. The interviewees also emphasized the significance of the gating system, particularly the thickness of the gating. As the gating undergoes solidification along with the casting, it retains substantial heat, which influences the overall temperature distribution of the megacast component. This, in turn, impacts the degree of distortion in the final part. The position of cooling channels , which are used to regulate the temperature of different parts of the die, play a crucial role in controlling the solidification rate. One respondent noted that if the die is designed with a focus on minimizing residual stresses, the cooling channels would be positioned closer to thicker sections to achieve balanced cooling. However, it was also pointed out that this approach, while beneficial for reducing residual stresses, might not be optimal for achieving desired mechanical properties. A consistent pouring temperature and rate prevent defects like misruns and cold shuts [ 12 ]. In the interviews, it was pointed out that uneven pouring leads to residual stress accumulation. The pouring temperature influences hardness, microstructure, and potentially geometrical quality by affecting metal flow and cooling. Pre-heating the die is also crucial to ensure uniform thermal conditions, reducing temperature gradients and minimizing distortions. The aluminum alloys’ characteristics affect the result, and an alloy with higher silicon content reduce soldering issues and improve flowability, minimizing geometrical variations [ 8 ], [ 13 ]. The ability to use recycled aluminum is important for sustainability and cost. Recycle-friendly alloys with higher tolerance to impurities will be required [ 14 ]. Casting parameters Die temperature and cooling rate significantly affect geometrical quality, as uneven cooling during solidification creates thermal gradients that lead to residual stresses and distortion [ 7 , 9 ]. In the interviews, the importance of closely monitoring die temperatures to prevent the formation of hot spots during solidification was highlighted. It was also mentioned that it is desirable to have uneven temperature distribution for megacasting, since the temperature at the end of the mold should be hotter than the gating area because the molten metal solidifies before reaching the end. The cooling or solidification time inside the cavity significantly affects the geometrical quality of cast parts. In the interviews, it was discussed that ejecting the part too early while it is still warm can result in bending, whereas waiting too long increases the risk of ejection difficulties due to shrinkage onto the die surface. It was also noted that cooling time can contribute to geometrical variations, especially for parts with thin sections that solidify faster than the biscuit, requiring longer wait times for complete solidification. It was also mentioned that reducing cooling time significantly, such as from 20 to 10 seconds, can leave the part semi-solid and prone to issues during ejection. However, increasing the cooling time beyond 20 seconds may not improve geometrical accuracy but would reduce productivity. Additionally, shrinkage is thought to be more influenced by temperature differences and cooling rates rather than the total time the part spends in the cavity. In [ 15 ], cooling time was not reported as a significant contributor to geometrical accuracy for a HPDC magnesium alloy component. Intensification pressure is the pressure applied during the solidification phase in HPDC. The effect of intensification pressure on geometrical accuracy depends on the part's size, shape, and design. Four interviewees noted that intensification pressure mainly affects areas near the ingate and might not reach all sections in designs with varying thicknesses, potentially impacting quality. One interviewee believed its overall influence on geometrical accuracy is minimal. According to [ 15 ] intensification pressure is the most critical parameter for controlling distortion in an AZ91D magnesium alloy component. Ejection The ejection stage is a critical phase in the casting process, as it introduces significant risks of mechanical deformation if not carefully managed [ 16 ]. The ejection mechanism is also related to draft angles, discussed in the section about part geometry. The ejection phase involves using ejection forces to remove the part from the die after it has solidified and cooled. Ejector forces depend on factors such as the alloy, release agent composition, locking time, intensification pressure, and the ejectors' pressure and speed [ 17 ]. The impact from the ejection forces on geometrical accuracy was also stressed during the interviews. Ideally, the forces should cause bending at the gate but can potentially lead to twisting of the part. Proper placement of the ejection pins is critical to ensure that the forces are evenly distributed and do not cause warping or distortion of the casting, as mentioned by the interviewees and in [ 18 ]. During the interviews, one expert highlighted that the number and placement of ejection pins should be designed to minimize ejection forces during the ejection phase. The ejection time indirectly influences defects such as soldering, which occurs when the casting sticks to the die surface. Soldering is especially problematic in hotter areas of the die, leading to surface damage, dimensional inaccuracies, and increased production downtime. Managing the ejection timing can help mitigate soldering by allowing the casting to cool sufficiently before removal, thereby reducing adhesion to the die. Moreover, ensuring adequate lubrication prior to injection can aid in controlling this issue by forming a protective barrier that eases the release of the casting [ 19 ]. Gripping methods can significantly affect the ejection phase by impacting how uniformly the casting is released from the die. In the interviews, it was noted that gripping methods are important, with robots typically gripping the biscuit for simplicity. However, alternative methods may be needed for certain designs, such as long and thin castings, to prevent distortion during handling [ 19 ]. Quenching The quenching process greatly affects the geometrical quality of megacast components, with parameters such as media temperature, immersion rate, and quench delay directly influencing residual stresses and distortion levels. Literature and interviews emphasize that a slow immersion rate increases the risk of severe distortion, particularly in parts with non-uniform thicknesses, where temperature differences exacerbate internal tensions [ 20 ], [ 21 ]. The importance of media selection and temperature is highlighted both in literature [ 21 ] and interviews, where the temperature difference between the part and the quenching media emerged as a key factor. Different quenchants have varying cooling rates depending on their composition and temperature. For aluminum, water is the most used quenching media. Excessively low media temperatures can lead to larger internal stresses, especially in parts with uneven thickness. Several interviewees hypothesized that a larger temperature difference increases distortion risks, as lower water temperatures exacerbate residual stresses. It was highlighted that to achieve the best mechanical properties and minimize distortion, the quench delay (the time between ejection from the mold and immersion into the quenching media) should be minimized. The quench time and the quench orientation are also frequently discussed [ 21 ]. In the interviews, some suggested that optimizing quench orientation could minimize warping, while others believed orientation had minimal impact as long as the entire casting was submerged. The time spent in the bath, however, was universally acknowledged as critical for controlling heat extraction levels. The fixturing during quenching is achieved using a gripper with multiple clamps that secure the part throughout the process. This gripper is designed to withstand the forces that could deform the megacast component during quenching, thereby helping the part retain its desired shape. Future tests of this approach are planned. In literature, racking of parts is discussed [ 22 ]. Here, the focus is however more to allow the uniform flow of heat around the parts when many parts are quenched in a rack. Trimming Trimming removes excess material such as overflows, runners and biscuits but can release residual stresses leading to spring back effects [ 5 ]. While some interviewees claimed that this stress release does not create new stresses or significantly impact geometrical accuracy, others argued that it could lead to deformation, especially if the removed areas, like the gating system, had been providing structural support to the casting. Tool alignment is another critical factor during trimming. Use of a trim press is the standard but also solutions using laser cutting are discussed. Misaligned tools can lead to uneven cuts, which affect the final geometry. The amount of information in literature about effects of trimming is limited, but recognized in [ 23 ]. 4. Physical tests As discussed in the previous section, megacasting is a complex process, and enhancing geometrical quality is not straightforward. Most parameters are interdependent and influenced by factors such as part geometry, material properties, and die conditions. Ensuring that the final component meets required material properties further constrains the extent to which process parameters can be adjusted to improve geometrical accuracy. Furthermore, casting machines are highly expensive, rendering trial-and-error methods that involve alterations to the die unreasonable. Figure 3 illustrates a megacast component where the geometrical quality does not meet the required standards. The red arrows highlight the problem, indicating deviations from nominal values in the directions specified by the arrows. To address this issue, physical tests related to the quenching process were conducted to find ways to minimize distortion while maintaining the material and strength properties of the component. Some tests needed to be discarded due to process issues, and therefore the sample sizes are largely varying. The tests shown in Table 1 were performed. The test conditions were selected based on the available process window; focusing on parameters that could realistically be adjusted in production without compromising material properties. All parts were scanned to assess distortion patterns, focusing particularly on the wheelhouse and front-leg areas. This revealed that the wheelhouse area was not very much affected by the process changes, while the “front leg” area showed larger differences. In the “front leg” area, manual measurements of the distance between the two “legs” were conducted, see Fig. 3 . Table 1 Overview of the physical tests. Test Description Sample size 1 Short quenching time - biscuit, ingate and "legs" not dipped. 6 2 Sequential/partial quenching: leg1 & wheelhouse1, then leg2, then wheelhouse2 6 3 As 2, but die temperature increased by 30°C 34 4 As 3, but no quenching of biscuit and runners 3 5 As 3, but solidification time in die increased 4 6 Increased die temperature, higher quench media temperature, longer quench time 8 While measurement values are not disclosed due to confidentiality, distribution and trends were analyzed statistically. The measurement results for the distance between the legs are presented in Fig. 4 a (Inspection Point A) and Fig. 4 b (Inspection Point B). Each figure includes a bubble plot, illustrating the frequency of observed values (with larger bubbles representing a greater number of samples), and a boxplot, summarizing the statistical distribution of each test. In the boxplot, the central box spans from the 25th to the 75th percentile, and the horizontal line within the box indicates the median. The values are not revealed due to confidentiality, but obviously, lower is better. The visualizations reveal several patterns: Test 1 exhibits substantial variation and a relatively high median. Test 2 shows improved performance compared to test 1, with both reduced variation and a lower median value. Test 3 , which was repeated numerous times, demonstrates consistent results, although the median remains higher than that of Test 2, particularly at Inspection Point A. Test 4 results in a pronounced deviation, indicating significant distortion. Tests 5 and 6 both yield stable outcomes, characterized by low variation and relatively low median values, suggesting reliable performance. Based on the test results, and considering the somewhat limited number of samples, Tests 5 and 6 yielded the best results. This aligns with interviews and literature studies, but the effect on mechanical and material properties must be further investigated. Due to cost and availability limitations, it was not feasible to perform comprehensive tests where all parameters were systematically varied. However, based on the tests conducted, the following adjustments were found to reduce distortion and positively impact geometrical quality: Increase die temperature Increase solidification time in die Increase quench media temperature Increase quench time 5. Results and Discussion Based on interviews and literature studies, it can be concluded that distortion in megacasting is a complex issue influenced by numerous interdependent design and process parameters. However, distortion is not the only important factor in megacasting. Material characteristics such as strength and durability must also meet safety requirements, and the prevention of cracks is equally critical. These characteristics are influenced by factors such as cooling rate and quenching parameters, which are also crucial for achieving geometric quality. The cycle time must also be kept down, eliminating solutions with too long quenching or solidification times. This study identifies die temperature, ejection pin position, ejection force, and the entire quenching process as the most critical yet somewhat adjustable parameters for achieving geometrical quality. These are marked with flags in Fig. 2 . One potential solution is to compensate for predicted and systematic distortions by adjusting the tool design. For instance, the tool could be constructed with slightly “wider legs”, anticipating the inward deviation of the legs after quenching. Here, simulation of distortion during megacasting is an important means to find suitable compensations in the tool. Avoiding trial-and-error iterations is crucial due to the high cost of tools used in megacasting, putting high demands on accuracy of simulation of the process. An additional novel approach, identified through expert interviews, is to secure the megacast component in a gripper that provides support to minimize distortion during quenching. If implemented, it will be crucial to design fixtures that accommodate the natural expansion and contraction of both the fixture and the component to avoid introducing additional stresses. To minimize distortion in megacast components, a combination of the aforementioned methods is recommended. Megacasting, as a relatively new manufacturing process, is still in its early stages of development, and both process knowledge and simulation capabilities are expected to improve significantly over time. With advancements in these areas, the majority of distortion can likely be mitigated through tool compensation strategies, such as designing tools to account for predictable deviations. For any remaining distortion, which is critical to meeting geometrical and functional requirements, minor adjustments to critical process parameters can be applied, potentially in combination with supportive fixturing during quenching. This approach provides additional control by stabilizing the part during quenching, preventing further deformation and ensuring the final component meets the desired specifications. The combination of these strategies offers a balanced and effective solution to address the complex challenges of distortion in megacasting. For future work, more tests need to be done to learn more about this complex process. Tests can also be used to validate and improve simulation capabilities to predict distortion in megacasting. With validated simulation capabilities, virtual tests can form a basis for further analysis of process parameter settings. 6. Conclusions Megacasting is a complex process and controlling distortion while maintaining geometrical quality in large castings with varying wall thicknesses presents a significant challenge. Critical parameters for reducing distortion were identified through interviews, literature studies, and physical tests. This study advances the field by integrating experimental and industrial insights to identify the most critical process parameters for reducing distortion. It establishes a foundation for integrating advanced compensation and fixturing techniques in megacasting, paving the way for more sustainable and efficient automotive manufacturing. Declarations Conflicts of interest The authors declare that they have no conflicts of interest relevant to this work. Funding This work was conducted at the Winquist Laboratory within the Area of Advance Production at Chalmers. It is a part of the project ”Geometrical robustness for mega casted aluminum parts, (GROMCAP), 2023 − 00802”, supported by the Strategic Vehicle Research and Innovation program at the Swedish Innovation Agency (VINNOVA). The support is gratefully acknowledged. Authors' contributions Kristina Wärmefjord: Conceptualization, Methodology, Formal analysis, Writing – original draft, Writing – review & editing, Supervision, Project administration, Funding acquisition. References Krajnik P, Hashimoto F, Karpuschewski B, da Silva EJ, Axinte D (2021) Grinding and fine finishing of future automotive powertrain components. CIRP Ann 70(2):589–610 Burggräf P, Bergweiler G, Kehrer S, Krawczyk T, Fiedler F (2024) Mega-casting in the automotive production system: Expert interview-based impact analysis of large-format aluminium high-pressure die-casting (HPDC) on the vehicle production. 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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-7233078","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":494721913,"identity":"5b10978e-5163-479c-aa19-2c7b1ec1de71","order_by":0,"name":"Kristina Waermefjord","email":"data:image/png;base64,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","orcid":"https://orcid.org/0000-0003-1556-3319","institution":"Chalmers tekniska högskola: Chalmers tekniska hogskola AB","correspondingAuthor":true,"prefix":"","firstName":"Kristina","middleName":"","lastName":"Waermefjord","suffix":""},{"id":494721914,"identity":"543927cc-b301-4432-99e1-6426cd0b8ad2","order_by":1,"name":"Josefin Hansen","email":"","orcid":"","institution":"","correspondingAuthor":false,"prefix":"","firstName":"Josefin","middleName":"","lastName":"Hansen","suffix":""},{"id":494721915,"identity":"b06eb77a-7c11-4d10-bd32-006201b6f69b","order_by":2,"name":"Rikard Söderberg","email":"","orcid":"","institution":"","correspondingAuthor":false,"prefix":"","firstName":"Rikard","middleName":"","lastName":"Söderberg","suffix":""}],"badges":[],"createdAt":"2025-07-28 10:56:07","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-7233078/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-7233078/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":88657467,"identity":"5e3af18b-aad4-41cb-9d8d-1292dc4297cc","added_by":"auto","created_at":"2025-08-08 19:45:13","extension":"jpeg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":493639,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cem\u003eTerminology of a megacast component.\u003c/em\u003e\u003c/p\u003e","description":"","filename":"floatimage1.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-7233078/v1/17d9d9f047edf9702821ec9c.jpeg"},{"id":88657465,"identity":"ff558a3f-b430-4828-9aac-53f2193f0f21","added_by":"auto","created_at":"2025-08-08 19:45:13","extension":"jpg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":47152,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cem\u003eDesign and process parameters critical to distortion in a megacast component. Parameters marked with a flag are identified as the most important ones, see discussion section.\u003c/em\u003e\u003c/p\u003e","description":"","filename":"Picture1.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7233078/v1/2c77f0e1a7edf1d6e9419740.jpg"},{"id":88657656,"identity":"c7e6e6ba-cbe1-4a21-8679-4e0bafdfd2b3","added_by":"auto","created_at":"2025-08-08 19:53:13","extension":"jpeg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":174465,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cem\u003eThe megacast component used in the tests. The arrows indicate unwanted distortion patterns in the wheelhouse area and of the 'front legs.'\u003c/em\u003e\u003c/p\u003e","description":"","filename":"floatimage3.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-7233078/v1/c39c50f980f9e21d72f66dca.jpeg"},{"id":88657471,"identity":"b007d7be-a2c5-4623-b1e8-77a9ad5032c8","added_by":"auto","created_at":"2025-08-08 19:45:13","extension":"jpeg","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":407384,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cem\u003e4a, 4b: Bubbleplot and boxplot for physical tests in two inspection points. The x-axis shows absolute value of deviation from nominal value. \u0026nbsp;Higher x-axis values indicate greater deviation from nominal geometry; smaller values are preferred. Due to confidentiality the values are not revealed.\u003c/em\u003e\u003c/p\u003e","description":"","filename":"floatimage4.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-7233078/v1/5a7b2d50aa12e979ce31a9a3.jpeg"},{"id":92671966,"identity":"da609d2c-2858-4388-981a-c4d0b0730e40","added_by":"auto","created_at":"2025-10-02 19:22:19","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1596587,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7233078/v1/f03f307c-50d6-46a4-9d1d-e3a21a13b924.pdf"}],"financialInterests":"","formattedTitle":"Advancing Strategies for Distortion Control in Megacasting: Critical Parameters and Compensation Techniques","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eThe automotive industry's pursuit of lightweight and sustainable solutions has led to significant advancements in manufacturing technologies [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. Among these, megacasting, also known as gigacasting, has emerged as a disruptive and transformative process, enabling the production of large, single-piece aluminum components that replace complex assemblies of up to hundreds of smaller parts. Cost savings in production are a primary driver [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. Environmental impacts related to weight savings are also highlighted, but in this context the recycling of aluminum should be equally emphasized for its significant contribution to sustainability [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]. Tesla introduced the concept of megacasting and secured a patent for its shock-absorbing properties in crash scenarios in 2022 [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. Megacasting has also been introduced as a competitive advantage by other brands, such as Mercedes-Benz, Volkswagen, Volvo Cars, and the Chinese brands Nio and Xpeng.\u003c/p\u003e\u003cp\u003eMegacasting enables the production of large, single-piece castings that consolidate multiple components, reducing the need for assembly. This functional integration can lead to improved structural integrity and reduced manufacturing complexity. The larger mass and complexity of megacast components compared to traditional HPDC necessitate advanced thermal management to ensure uniform solidification and minimize defects like porosity or warping.\u003c/p\u003e\u003cp\u003eHowever, the adoption of megacasting introduces challenges [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. In this paper, the focus is on geometrical quality; the degree to which a manufactured component conforms to its intended shape and dimensions [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e], ruled by tolerances. Ensuring high geometrical quality is critical for maintaining structural integrity, assembly precision, and overall vehicle quality and performance. Geometrical variation in components can propagate through subassemblies and affect the visual quality impressions related to flush and gaps in split lines of the produced vehicle. Large, thin-walled castings are especially sensitive to issues such as distortion, warping, and residual stresses due to the complex interplay of process parameters, such as variations in cooling rates across different areas or differences in section thickness. During solidification and cooling, the castings contract, interacting with constraints such as die walls. This interaction generates residual stresses, leading to complex spring back and continued warping during post-ejection cooling. In complex-shaped castings, non-uniform cooling conditions can cause plastic strain, resulting in permanent distortion [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eCompared to traditional sheet metal assemblies, where hundreds of parts are joined together, megacasting significantly shortens the tolerance chain by eliminating the need for spot welding or other joining methods in numerous assembly stations in the production flow. However, this also removes the possibility of compensation steps, such as using lap joints in sheet metal assemblies, which allow for the joining of non-nominal parts while still meeting assembly requirements. As a result, ensuring the geometrical quality of megacast components becomes critical, as deviations cannot be corrected during an intermediate assembly stage.\u003c/p\u003e\u003cp\u003eAddressing these challenges requires a comprehensive understanding of the factors influencing geometrical quality, including material properties, die design, quenching techniques, and trimming processes.\u003c/p\u003e\u003cdiv id=\"Sec2\" class=\"Section2\"\u003e\u003ch2\u003e1.1. Scope of the paper\u003c/h2\u003e\u003cp\u003eThis paper aims to explore the key parameters affecting geometrical quality in megacasting, drawing insights from literature, industry practices, and experimental tests. By identifying the root causes of variation and proposing strategies for improvement, this study contributes to the advancement of megacasting technologies, supporting the automotive industry's goals of achieving cost-efficient, sustainable, and high-quality vehicle components.\u003c/p\u003e\u003cp\u003eIn Section 2, the methodology is described. Section 3 focuses on the results from expert interviews and literature reviews. Section 4 describes the physical tests that have been performed, while Section 5 presents the results and discussion. Conclusions are found in Section 6.\u003c/p\u003e\u003c/div\u003e"},{"header":"2. Methodology","content":"\u003cp\u003eThe findings in this paper are based on a combination of three qualitative and experimental approaches. Insights were gathered through 12 semi-structured interviews with process engineers, designers, and quality assurance specialists from academia and industry, selected based on their extensive experience in high-pressure die casting (HPDC) and an interest in megacasting. These interviews offered valuable perspectives on the practical challenges and variability of key process parameters affecting geometrical quality, as well as new ideas for megacasting quality assurance. The interviews were recorded, transcribed, and systematically analyzed, providing critical knowledge about factors influencing geometrical quality and the challenges encountered in real-world applications.\u003c/p\u003e\u003cp\u003eIn parallel, a targeted review of relevant literature was carried out to map contributors to geometrical variation, focusing on aspects such as die design, quenching techniques, and material properties. The search employed keywords like \u0026ldquo;megacasting\u0026rdquo;, \"geometrical variation\", \"dimensional variation\", \"distortions in HPDC components\", \"hyper-casting\", \"giga-press\u0026rdquo;, \"shrinkage\", \"twisting\" and \"large casting\" to identify relevant scientific sources.\u003c/p\u003e\u003cp\u003eAdditionally, a limited number of physical tests were performed in an industrial setting to investigate the effects of process parameters, including die temperature, quench media temperature, quench orientation, and quench time, on distortion in megacast components.\u003c/p\u003e"},{"header":"3. Factors Influencing Geometrical Quality in HPDC","content":"\u003cp\u003eMegacasting is a form of HPDC, distinguished primarily by the sheer size of the components produced. Using Giga Presses capable of exerting clamping forces exceeding 9,000 tons, this process enables the creation of large, single-piece castings. However, the increased mass and geometric complexity introduce significant challenges\u0026mdash;particularly in managing heat flow and solidification. More advanced thermal control, compared to traditional HPDC, is therefore critical to ensure uniform solidification and to reduce the risk of defects such as porosity, warping, and residual stresses.\u003c/p\u003e\u003cp\u003eThe casting process contains many steps, each of them providing its own challenges and contributors to geometrical variation in the produced megacast components. The main process steps are considered in this section, together with a discussion based on interviews and literature about the factors affecting geometrical quality. Some steps have been consolidated, or even excluded, to align with the objectives of this paper.\u003c/p\u003e\u003cp\u003eFigure \u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e introduces some terminology of a megacast component. Figure\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e illustrates the factors discussed in this section, where the letters \u003cem\u003ei\u003c/em\u003e, \u003cem\u003el\u003c/em\u003e and \u003cem\u003et\u003c/em\u003e indicate the source of information (interviews (\u003cem\u003ei\u003c/em\u003e), literature studies (\u003cem\u003el\u003c/em\u003e) or physical tests (\u003cem\u003et\u003c/em\u003e)).\u003c/p\u003e\u003cp\u003eDie-casting machine characteristics, such as die stiffness, maximum locking force and injection pressure are excluded from this discussion.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003cb\u003ePart geometry\u003c/b\u003e\u003c/p\u003e\u003cp\u003eThe design of the megacasted part geometry determines the foundation for geometrical quality by influencing cooling behavior, residual stresses, and distortions. Many requirements on function, cost and producibility must be met, but here the focus is on risk of distortion.\u003c/p\u003e\u003cp\u003eThe part's geometry significantly influences the risk of deviation from its nominal shape. \u003cem\u003eComplex geometries\u003c/em\u003e, including large components, are more prone to amplifying residual stress development [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e], increasing the likelihood of distortions and variations. Additionally, varying \u003cem\u003ewall thicknesses\u003c/em\u003e can create uneven cooling rates, leading to residual stresses that result in distortions [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e, \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]. During the interviews, it was also mentioned that the cooling system can be used to compensate for the varying thickness.\u003c/p\u003e\u003cp\u003eIncorporating \u003cem\u003edraft angles\u003c/em\u003e into the design is beneficial from a geometry assurance perspective according to the interviewees. Draft angles help mitigate issues during ejection, as parts that shrink and adhere to the die may require increased ejection forces for release, potentially causing deformations [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e].\u003c/p\u003e\u003cp\u003e\u003cb\u003eDie and Material\u003c/b\u003e\u003c/p\u003e\u003cp\u003eDie design plays a crucial role in the quality of high-pressure die cast components, as it directly impacts material flow, solidification, and cooling. The \u003cem\u003egating system\u003c/em\u003e, with its key features such as runners, ingates, and the biscuit (see Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e) are carefully designed to ensure the molten metal fills the die cavity uniformly and without turbulence, minimizing defects like air entrapment or cold shuts. The runners guide the molten metal into the die, while the ingate controls the entry of metal into the cavity, balancing flow and pressure. The biscuit, located at the end of the shot sleeve, acts as a reservoir to maintain pressure during solidification, preventing shrinkage-related defects. Proper design of these features also helps optimize the thermal behavior of the casting and reduce residual stresses. Furthermore, the contraction of the gating system during solidification can drag the other sections of the casting causing distortion and hot tearing [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]. The interviewees also emphasized the significance of the gating system, particularly the thickness of the gating. As the gating undergoes solidification along with the casting, it retains substantial heat, which influences the overall temperature distribution of the megacast component. This, in turn, impacts the degree of distortion in the final part.\u003c/p\u003e\u003cp\u003eThe position of \u003cem\u003ecooling channels\u003c/em\u003e, which are used to regulate the temperature of different parts of the die, play a crucial role in controlling the solidification rate. One respondent noted that if the die is designed with a focus on minimizing residual stresses, the cooling channels would be positioned closer to thicker sections to achieve balanced cooling. However, it was also pointed out that this approach, while beneficial for reducing residual stresses, might not be optimal for achieving desired mechanical properties.\u003c/p\u003e\u003cp\u003eA consistent \u003cem\u003epouring temperature and rate\u003c/em\u003e prevent defects like misruns and cold shuts [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]. In the interviews, it was pointed out that uneven pouring leads to residual stress accumulation. The pouring temperature influences hardness, microstructure, and potentially geometrical quality by affecting metal flow and cooling. Pre-heating the die is also crucial to ensure uniform thermal conditions, reducing temperature gradients and minimizing distortions.\u003c/p\u003e\u003cp\u003eThe aluminum \u003cem\u003ealloys\u0026rsquo; characteristics\u003c/em\u003e affect the result, and an alloy with higher silicon content reduce soldering issues and improve flowability, minimizing geometrical variations [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e], [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]. The ability to use recycled aluminum is important for sustainability and cost. Recycle-friendly alloys with higher tolerance to impurities will be required [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e].\u003c/p\u003e\u003cp\u003e\u003cb\u003eCasting parameters\u003c/b\u003e\u003c/p\u003e\u003cp\u003eDie temperature and cooling rate significantly affect geometrical quality, as uneven cooling during solidification creates thermal gradients that lead to residual stresses and distortion [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e, \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]. In the interviews, the importance of closely monitoring \u003cem\u003edie temperatures\u003c/em\u003e to prevent the formation of hot spots during solidification was highlighted. It was also mentioned that it is desirable to have uneven temperature distribution for megacasting, since the temperature at the end of the mold should be hotter than the gating area because the molten metal solidifies before reaching the end.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eThe cooling or \u003cem\u003esolidification time\u003c/em\u003e inside the cavity significantly affects the geometrical quality of cast parts. In the interviews, it was discussed that ejecting the part too early while it is still warm can result in bending, whereas waiting too long increases the risk of ejection difficulties due to shrinkage onto the die surface. It was also noted that cooling time can contribute to geometrical variations, especially for parts with thin sections that solidify faster than the biscuit, requiring longer wait times for complete solidification. It was also mentioned that reducing cooling time significantly, such as from 20 to 10 seconds, can leave the part semi-solid and prone to issues during ejection. However, increasing the cooling time beyond 20 seconds may not improve geometrical accuracy but would reduce productivity. Additionally, shrinkage is thought to be more influenced by temperature differences and cooling rates rather than the total time the part spends in the cavity. In [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e], cooling time was not reported as a significant contributor to geometrical accuracy for a HPDC magnesium alloy component.\u003c/p\u003e\u003cp\u003e\u003cem\u003eIntensification pressure\u003c/em\u003e is the pressure applied during the solidification phase in HPDC. The effect of intensification pressure on geometrical accuracy depends on the part's size, shape, and design. Four interviewees noted that intensification pressure mainly affects areas near the ingate and might not reach all sections in designs with varying thicknesses, potentially impacting quality. One interviewee believed its overall influence on geometrical accuracy is minimal. According to [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e] intensification pressure is the most critical parameter for controlling distortion in an AZ91D magnesium alloy component.\u003c/p\u003e\u003cp\u003e\u003cb\u003eEjection\u003c/b\u003e\u003c/p\u003e\u003cp\u003eThe ejection stage is a critical phase in the casting process, as it introduces significant risks of mechanical deformation if not carefully managed [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]. The ejection mechanism is also related to draft angles, discussed in the section about part geometry.\u003c/p\u003e\u003cp\u003eThe ejection phase involves using \u003cem\u003eejection forces\u003c/em\u003e to remove the part from the die after it has solidified and cooled. Ejector forces depend on factors such as the alloy, release agent composition, locking time, intensification pressure, and the ejectors' pressure and speed [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]. The impact from the ejection forces on geometrical accuracy was also stressed during the interviews. Ideally, the forces should cause bending at the gate but can potentially lead to twisting of the part. Proper placement of the \u003cem\u003eejection pins\u003c/em\u003e is critical to ensure that the forces are evenly distributed and do not cause warping or distortion of the casting, as mentioned by the interviewees and in [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e]. During the interviews, one expert highlighted that the number and placement of ejection pins should be designed to minimize ejection forces during the ejection phase.\u003c/p\u003e\u003cp\u003eThe \u003cem\u003eejection time\u003c/em\u003e indirectly influences defects such as soldering, which occurs when the casting sticks to the die surface. Soldering is especially problematic in hotter areas of the die, leading to surface damage, dimensional inaccuracies, and increased production downtime. Managing the ejection timing can help mitigate soldering by allowing the casting to cool sufficiently before removal, thereby reducing adhesion to the die. Moreover, ensuring adequate lubrication prior to injection can aid in controlling this issue by forming a protective barrier that eases the release of the casting [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e].\u003c/p\u003e\u003cp\u003e\u003cem\u003eGripping methods\u003c/em\u003e can significantly affect the ejection phase by impacting how uniformly the casting is released from the die. In the interviews, it was noted that gripping methods are important, with robots typically gripping the biscuit for simplicity. However, alternative methods may be needed for certain designs, such as long and thin castings, to prevent distortion during handling [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e].\u003c/p\u003e\u003cp\u003e\u003cb\u003eQuenching\u003c/b\u003e\u003c/p\u003e\u003cp\u003eThe quenching process greatly affects the geometrical quality of megacast components, with parameters such as media temperature, immersion rate, and quench delay directly influencing residual stresses and distortion levels. Literature and interviews emphasize that a slow \u003cem\u003eimmersion rate\u003c/em\u003e increases the risk of severe distortion, particularly in parts with non-uniform thicknesses, where temperature differences exacerbate internal tensions [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e], [\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eThe importance of \u003cem\u003emedia selection and temperature\u003c/em\u003e is highlighted both in literature [\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e] and interviews, where the temperature difference between the part and the quenching media emerged as a key factor. Different quenchants have varying cooling rates depending on their composition and temperature. For aluminum, water is the most used quenching media. Excessively low media temperatures can lead to larger internal stresses, especially in parts with uneven thickness. Several interviewees hypothesized that a larger temperature difference increases distortion risks, as lower water temperatures exacerbate residual stresses. It was highlighted that to achieve the best mechanical properties and minimize distortion, the quench delay (the time between ejection from the mold and immersion into the quenching media) should be minimized.\u003c/p\u003e\u003cp\u003eThe \u003cem\u003equench time\u003c/em\u003e and the \u003cem\u003equench orientation\u003c/em\u003e are also frequently discussed [\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e]. In the interviews, some suggested that optimizing quench orientation could minimize warping, while others believed orientation had minimal impact as long as the entire casting was submerged. The time spent in the bath, however, was universally acknowledged as critical for controlling heat extraction levels.\u003c/p\u003e\u003cp\u003eThe \u003cem\u003efixturing\u003c/em\u003e during quenching is achieved using a gripper with multiple clamps that secure the part throughout the process. This gripper is designed to withstand the forces that could deform the megacast component during quenching, thereby helping the part retain its desired shape. Future tests of this approach are planned. In literature, racking of parts is discussed [\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e]. Here, the focus is however more to allow the uniform flow of heat around the parts when many parts are quenched in a rack.\u003c/p\u003e\u003cp\u003e\u003cb\u003eTrimming\u003c/b\u003e\u003c/p\u003e\u003cp\u003eTrimming removes excess material such as overflows, runners and biscuits but can release residual stresses leading to \u003cem\u003espring back\u003c/em\u003e effects [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. While some interviewees claimed that this stress release does not create new stresses or significantly impact geometrical accuracy, others argued that it could lead to deformation, especially if the removed areas, like the gating system, had been providing structural support to the casting.\u003c/p\u003e\u003cp\u003e\u003cem\u003eTool alignment\u003c/em\u003e is another critical factor during trimming. Use of a trim press is the standard but also solutions using laser cutting are discussed. Misaligned tools can lead to uneven cuts, which affect the final geometry. The amount of information in literature about effects of trimming is limited, but recognized in [\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e].\u003c/p\u003e"},{"header":"4. Physical tests","content":"\u003cp\u003eAs discussed in the previous section, megacasting is a complex process, and enhancing geometrical quality is not straightforward. Most parameters are interdependent and influenced by factors such as part geometry, material properties, and die conditions. Ensuring that the final component meets required material properties further constrains the extent to which process parameters can be adjusted to improve geometrical accuracy. Furthermore, casting machines are highly expensive, rendering trial-and-error methods that involve alterations to the die unreasonable.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eFigure \u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e illustrates a megacast component where the geometrical quality does not meet the required standards. The red arrows highlight the problem, indicating deviations from nominal values in the directions specified by the arrows. To address this issue, physical tests related to the quenching process were conducted to find ways to minimize distortion while maintaining the material and strength properties of the component. Some tests needed to be discarded due to process issues, and therefore the sample sizes are largely varying. The tests shown in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e were performed. The test conditions were selected based on the available process window; focusing on parameters that could realistically be adjusted in production without compromising material properties.\u003c/p\u003e\u003cp\u003eAll parts were scanned to assess distortion patterns, focusing particularly on the wheelhouse and front-leg areas. This revealed that the wheelhouse area was not very much affected by the process changes, while the \u0026ldquo;front leg\u0026rdquo; area showed larger differences. In the \u0026ldquo;front leg\u0026rdquo; area, manual measurements of the distance between the two \u0026ldquo;legs\u0026rdquo; were conducted, see Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\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\u003eOverview of the physical tests.\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"3\"\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=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eTest\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eDescription\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eSample size\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=\"left\" colname=\"c2\"\u003e\u003cp\u003eShort quenching time - biscuit, ingate and \"legs\" not dipped.\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e6\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=\"left\" colname=\"c2\"\u003e\u003cp\u003eSequential/partial quenching: leg1 \u0026amp; wheelhouse1, then leg2, then wheelhouse2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e6\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=\"left\" colname=\"c2\"\u003e\u003cp\u003eAs 2, but die temperature increased by 30\u0026deg;C\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e34\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=\"left\" colname=\"c2\"\u003e\u003cp\u003eAs 3, but no quenching of biscuit and runners\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e3\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=\"left\" colname=\"c2\"\u003e\u003cp\u003eAs 3, but solidification time in die increased\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e4\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=\"left\" colname=\"c2\"\u003e\u003cp\u003eIncreased die temperature, higher quench media temperature, longer quench time\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e8\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\u003eWhile measurement values are not disclosed due to confidentiality, distribution and trends were analyzed statistically. The measurement results for the distance between the legs are presented in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ea (Inspection Point A) and Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eb (Inspection Point B). Each figure includes a bubble plot, illustrating the frequency of observed values (with larger bubbles representing a greater number of samples), and a boxplot, summarizing the statistical distribution of each test. In the boxplot, the central box spans from the 25th to the 75th percentile, and the horizontal line within the box indicates the median. The values are not revealed due to confidentiality, but obviously, lower is better.\u003c/p\u003e\u003cp\u003eThe visualizations reveal several patterns:\u003c/p\u003e\u003cp\u003e\u003cul\u003e\u003cli\u003e\u003cp\u003e\u003cb\u003eTest 1\u003c/b\u003e exhibits substantial variation and a relatively high median.\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003e\u003cb\u003eTest 2\u003c/b\u003e shows improved performance compared to test 1, with both reduced variation and a lower median value.\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003e\u003cb\u003eTest 3\u003c/b\u003e, which was repeated numerous times, demonstrates consistent results, although the median remains higher than that of Test 2, particularly at Inspection Point A.\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003e\u003cb\u003eTest 4\u003c/b\u003e results in a pronounced deviation, indicating significant distortion.\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003e\u003cb\u003eTests 5 and 6\u003c/b\u003e both yield stable outcomes, characterized by low variation and relatively low median values, suggesting reliable performance.\u003c/p\u003e\u003c/li\u003e\u003c/ul\u003e\u003c/p\u003e\u003cp\u003eBased on the test results, and considering the somewhat limited number of samples, Tests 5 and 6 yielded the best results. This aligns with interviews and literature studies, but the effect on mechanical and material properties must be further investigated.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eDue to cost and availability limitations, it was not feasible to perform comprehensive tests where all parameters were systematically varied. However, based on the tests conducted, the following adjustments were found to reduce distortion and positively impact geometrical quality:\u003c/p\u003e\u003cp\u003e\u003cul\u003e\u003cli\u003e\u003cp\u003eIncrease die temperature\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003eIncrease solidification time in die\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003eIncrease quench media temperature\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003eIncrease quench time\u003c/p\u003e\u003c/li\u003e\u003c/ul\u003e\u003c/p\u003e"},{"header":"5. Results and Discussion","content":"\u003cp\u003eBased on interviews and literature studies, it can be concluded that distortion in megacasting is a complex issue influenced by numerous interdependent design and process parameters. However, distortion is not the only important factor in megacasting. Material characteristics such as strength and durability must also meet safety requirements, and the prevention of cracks is equally critical. These characteristics are influenced by factors such as cooling rate and quenching parameters, which are also crucial for achieving geometric quality. The cycle time must also be kept down, eliminating solutions with too long quenching or solidification times. This study identifies die temperature, ejection pin position, ejection force, and the entire quenching process as the most critical yet somewhat adjustable parameters for achieving geometrical quality. These are marked with flags in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e.\u003c/p\u003e\u003cp\u003eOne potential solution is to compensate for predicted and systematic distortions by adjusting the tool design. For instance, the tool could be constructed with slightly \u0026ldquo;wider legs\u0026rdquo;, anticipating the inward deviation of the legs after quenching. Here, simulation of distortion during megacasting is an important means to find suitable compensations in the tool. Avoiding trial-and-error iterations is crucial due to the high cost of tools used in megacasting, putting high demands on accuracy of simulation of the process.\u003c/p\u003e\u003cp\u003eAn additional novel approach, identified through expert interviews, is to secure the megacast component in a gripper that provides support to minimize distortion during quenching. If implemented, it will be crucial to design fixtures that accommodate the natural expansion and contraction of both the fixture and the component to avoid introducing additional stresses.\u003c/p\u003e\u003cp\u003eTo minimize distortion in megacast components, a combination of the aforementioned methods is recommended. Megacasting, as a relatively new manufacturing process, is still in its early stages of development, and both process knowledge and simulation capabilities are expected to improve significantly over time. With advancements in these areas, the majority of distortion can likely be mitigated through tool compensation strategies, such as designing tools to account for predictable deviations. For any remaining distortion, which is critical to meeting geometrical and functional requirements, minor adjustments to critical process parameters can be applied, potentially in combination with supportive fixturing during quenching. This approach provides additional control by stabilizing the part during quenching, preventing further deformation and ensuring the final component meets the desired specifications. The combination of these strategies offers a balanced and effective solution to address the complex challenges of distortion in megacasting.\u003c/p\u003e\u003cp\u003eFor future work, more tests need to be done to learn more about this complex process. Tests can also be used to validate and improve simulation capabilities to predict distortion in megacasting. With validated simulation capabilities, virtual tests can form a basis for further analysis of process parameter settings.\u003c/p\u003e"},{"header":"6. Conclusions","content":"\u003cp\u003eMegacasting is a complex process and controlling distortion while maintaining geometrical quality in large castings with varying wall thicknesses presents a significant challenge. Critical parameters for reducing distortion were identified through interviews, literature studies, and physical tests. This study advances the field by integrating experimental and industrial insights to identify the most critical process parameters for reducing distortion. It establishes a foundation for integrating advanced compensation and fixturing techniques in megacasting, paving the way for more sustainable and efficient automotive manufacturing.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003ch2\u003eConflicts of interest\u003c/h2\u003e\u003cp\u003eThe authors declare that they have no conflicts of interest relevant to this work.\u003c/p\u003e\u003c/p\u003e\u003ch2\u003eFunding\u003c/h2\u003e\u003cp\u003eThis work was conducted at the Winquist Laboratory within the Area of Advance Production at Chalmers. It is a part of the project \u0026rdquo;Geometrical robustness for mega casted aluminum parts, (GROMCAP), 2023\u0026thinsp;\u0026minus;\u0026thinsp;00802\u0026rdquo;, supported by the Strategic Vehicle Research and Innovation program at the Swedish Innovation Agency (VINNOVA). The support is gratefully acknowledged.\u003c/p\u003e\u003ch2\u003eAuthors' contributions\u003c/h2\u003e\u003cp\u003eKristina W\u0026auml;rmefjord: Conceptualization, Methodology, Formal analysis, Writing \u0026ndash; original draft, Writing \u0026ndash; review \u0026amp; editing, Supervision, Project administration, Funding acquisition.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eKrajnik P, Hashimoto F, Karpuschewski B, da Silva EJ, Axinte D (2021) Grinding and fine finishing of future automotive powertrain components. CIRP Ann 70(2):589\u0026ndash;610\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eBurggr\u0026auml;f P, Bergweiler G, Kehrer S, Krawczyk T, Fiedler F (2024) Mega-casting in the automotive production system: Expert interview-based impact analysis of large-format aluminium high-pressure die-casting (HPDC) on the vehicle production. J Manuf Process 124:918\u0026ndash;935\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eBleicher C, Qaralleh A, Lehmhus D, Haesche M, Gomes LF, Pintore M, Kleinhans R, Sommer S, Tlatlik J (2025) Aspects for the Optimization of Car Production Regarding Efficiency, Availability and Sustainability, No. 0148\u0026ndash;7191, SAE Technical Paper.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eTESLA I (2022) INTEGRATED ENERGY ABSORBING CASTINGS, PCT/US2021/044780.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eW\u0026auml;rmefjord K, Hansen J, S\u0026ouml;derberg R (2023) Challenges in geometry assurance of megacasting in the automotive industry. J Comput Inf Sci Eng 23(6):060801\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eS\u0026ouml;derberg R, W\u0026auml;rmefjord K, Carlson JS, Lindkvist L (2017) Toward a Digital Twin for real-time geometry assurance in individualized production. CIRP Ann 66(1):137\u0026ndash;140\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eCampatelli G, Scippa A (2012) A heuristic approach to meet geometric tolerance in high pressure die casting. Simul Model Pract Theory 22:109\u0026ndash;122\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eCasarotto F, Franke A, Franke R (2012) High-pressure die-cast (HPDC) aluminium alloys for automotive applications, Advanced materials in automotive engineering. Elsevier, pp 109\u0026ndash;149\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eHofer P, Kaschnitz E, Schumacher P (2014) Distortion and residual stress in high-pressure die castings: simulation and measurements. J Minerals Met Mater Soc 66:1638\u0026ndash;1646\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eEl Mehtedi M, Mancia T, Buonadonna P, Guzzini L, Santini E, Forcellese A (2020) Design optimization of gate system on high pressure die casting of AlSi13Fe alloy by means of finite element simulations. Procedia CIRP 88:509\u0026ndash;514\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eIqbal M (2014) Gating design criteria for sound casting. Int J Mech Eng Rob Res 3(3):675\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eAkili C, Bouayad A, Alami M (2015) The effect of mold and pouring temperature on hardness and microstructure of a HPDC hyper-eutectic aluminum alloy. Int J Eng Res Technol 4(3):1162\u0026ndash;1165\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eMakhlouf MM, Apelian D (2002) Casting characteristics of aluminum die casting alloys. 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Mater Trans 63(2):217\u0026ndash;223\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eKrischke S, M\u0026uuml;ller S, Schuchardt T, Kouki Y, Dilger K (2018) Experimental Investigations on the Ejector Forces in the Die Casting Process. Arch Foundry Eng 18(4):116\u0026ndash;119\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eK\u0026ouml;ser O, R\u0026uuml;ckert J, Ubl P Modeling and optimization of part ejection in magnesium high pressure die casting, Proc. European Metallurgical Conference, pp. 14\u0026ndash;17\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eMonroe A, Sanders P (2021) The need for a new approach to soldering in high pressure die casting. Int J Metalcast 15(2):391\u0026ndash;397\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eTiryakioglu M, Totten G Quenching aluminum components in water: Problems and alternatives, Proc. Heat Treating: Proceedings of the 18 th Conference, October 12 th-15 th\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eMacKenzie S (2020) Quenching aluminum for residual stress and distortion control. J Heat Treat Mater 75(1):23\u0026ndash;34\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eMacKenzie DS Quenching and the Control of Residual Stresses and Distortion in Aluminum, Proc. International Conference on Structural Aluminum Casting\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eBharambe C, Jaybhaye M, Dalmiya A, Daund C, Shinde D (2023) Analyzing casting defects in high-pressure die casting industrial case study, Materials Today: Proceedings, 72, pp. 1079\u0026ndash;1083\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":false,"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":"Quality Assurance, Casting, Tolerances, Distortion","lastPublishedDoi":"10.21203/rs.3.rs-7233078/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7233078/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eMegacasting, also known as gigacasting, is an emerging high-pressure die casting (HPDC) technology that enables the production of large, complex aluminum components in a single piece. This disruptive approach offers potential benefits in terms of reduced part count, lower assembly cost, and improved structural performance. However, the process also introduces significant challenges in maintaining tight geometrical tolerances due to distortion caused by residual stresses and non-uniform cooling. This study advances strategies for minimizing distortion by combining insights from interviews, physical tests, and literature. Key process parameters, including tool compensation, quenching, and fixturing, are identified and analyzed. A balanced approach is proposed, integrating predictive tool compensation and fixturing during quenching to reduce distortion. The findings present a novel framework for controlling distortion while meeting both material and geometrical quality requirements in megacast components, paving the way for more sustainable and competitive manufacturing practices in the automotive industry.\u003c/p\u003e\u003cp\u003eThis paper represents one of the first structured efforts to integrate empirical shop-floor experience, existing literature, and early-stage testing to address distortion control in megacasting.\u003c/p\u003e","manuscriptTitle":"Advancing Strategies for Distortion Control in Megacasting: Critical Parameters and Compensation Techniques","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-08-08 19:45:08","doi":"10.21203/rs.3.rs-7233078/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":"ad686035-04fb-42f6-a94f-65535f4feae6","owner":[],"postedDate":"August 8th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2025-10-02T19:14:12+00:00","versionOfRecord":[],"versionCreatedAt":"2025-08-08 19:45:08","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-7233078","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7233078","identity":"rs-7233078","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}