Ji-Woo Park

Flexible Die Design and Springback Compensation Based on Modified Displacement Adjustment Method

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.

Study on stretching effect of multiple die forming technology

The multiple die forming (MDF) technology is suitable for flexible manufacturing, and it affords several advantages including its applicability to various forming processes such as single-curved surface forming, and double-curved surface forming. In sheet metal forming process, the elastic recovery has become a problem. Therefore, the stretch forming process is applied MDF technology to reduce elastic recovery effect. Numerical simulation is carried out for a saddle-type surface forming using ABAQUS. Every simulation case performs spring-back analysis to find elastic recovery effect after forming simulation. In this simulation, urethane pads are defined based on a hyperelastic material model as a cushion for the smoothness of forming surface. The elastic recovery deformation behavior is also investigated to consider the exact result after the last forming process, and then, the actual experiments are performed to confirm the formability of this forming process. By comparing the simulation and the experime...