Design and dispensing volume estimation of a single piezo-driven dispenser with rigid-flexible combined transmission mechanism

Abstract To solve the problems of entire replacement due to fatigue of the flexible part, the preload structure is easy to loosen or the preloading force cannot be adjusted, and the volume of adhesive droplets is difficult to estimate. A rigid-flexible combined mechanism with a unilateral preloading feature was introduced, and a droplet volume estimation method was proposed. Firstly, the principle of the single piezo-driven dispenser was analyzed, a static model of the displacement transmission mechanism was established, and the transmission ratio was designed. Secondly, based on the limiting method and the curtain area assumption, a linearized dispensing volume estimation model was proposed, then the fluid simulation model was established and the localized high-pressure of the chamber was simulated to verify the theoretical model. Lastly, a dispenser prototype was manufactured and tested. The results show that the designed dispenser worked stably, with a droplet consistency of diameter within 4.22%. The relative error average (REA) of localized high pressure between the simulation and theory was within 6.5%, and the trend of the measured droplet volume is consistent with the theory under different control parameters, which has a REA of within 5.3%, verifying the feasibility of the proposed droplet volume estimation model. When the dispensing frequency reached 400 Hz, the minimum diameter and volume were 0.43 mm and 0.092 ul, respectively. Experiments show that the designed structure and theoretical model are reliable.