Abstract
Springback in metal forming process often results in undesirable shape changes in formed parts and leads to deterioration in product quality. Even though springback can be predicted and compensated for through the theories or methodologies established thus far, an increase in manufacturing cost accompanied by a change in die shape is inevitable. In the present paper, it is suggested that the cost accompanied with springback compensation can be minimized while allowing the processing of various three-dimensional curved surfaces by using a flexible die composed of multiple punches. With the die being very flexible, the iterative trial-and-error method can be readily applied to compensate for the springback. Thus, repeated designing and redesigning of solid or matched dies can be avoided, effectively saving considerable time. Only some adjustments of punch height are required. Detailed designs of the flexible die as well as two core algorithms to control the respective punch heights are described in this paper. In addition, a closed-loop system for the springback compensation using the flexible die is proposed. The amount of springback was simulated by a finite element analysis and the modified displacement adjustment (DA) method as the springback compensation model was used in the closed-loop system. This system was applied to a two-dimensional quadratic shape problem, and its robustness was verified by an experiment.
Highlights
Springback occurring with removal of constraints is a major cause of shape error in metal forming process and many scientific investigations to eliminate or compensate the shape error have been reported
Studies on optimizing the forming parameters such as die shape, blank holder force [2], friction [5], and the ratio of radius of curvature to sheet thickness (R/t) [6] and utilizing the hardening model [7] and Bauschinger effect [6, 8] have been carried out to eliminate or reduce the springback, their results are largely dependent on forming processes or material conditions
The flexible forming technique and a modified displacement adjustment (DA) method based on FE simulations were used
Summary
Springback occurring with removal of constraints is a major cause of shape error in metal forming process and many scientific investigations to eliminate or compensate the shape error have been reported. Advanced models of compensation such as an accelerated springback compensation method [3], the smooth displacement adjustment (SDA) [13], the surface controlled overbending (SCO) [13], and a combined model with an optimization scheme [14] were suggested, it is difficult to reduce cost and work in practice. To solve this problem, in this work, springback compensation model was employed using a flexible die.
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