Research on Springback Control in Stretch Bending Based on Iterative Compensation Method

An unavoidable problem in the stretch-bending process is springback, which dictates the shape and dimensional accuracy of the product. This problem can be solved by adjusting the geometry of the die or through active process control. This study focuses on the design of the die shape to achieve the target product. Based on the fixed-point iterative method and displacement adjustment (DA) method, this paper proposes an iterative compensation method, which has a higher convergence rate, lower number of iterations, and higher precision compared to the DA method with only one control parameter. In addition, like the DA method, the proposed method does not depend on the material properties or mechanical model, but the difference is that it can quickly and effectively find out the iteration parameter, determine whether the parameter has convergence or not, and has no compensation factor. According to the deviation of iterative parameters between the value after stretch bending and the target value, the iterative compensation method can be used to calculate the compensation magnitude and compensation direction of the iterative parameter. For stretch-bending processes with invariable- and variable-curvature die shapes, the convergence of control parameters is verified mathematically with the convergence theorem of the method, and experiments are conducted to verify the iterative compensation method. The experimental results show that the target products can be obtained with a small number of iterations without knowing the specific material properties.