Springback Compensation Strategy Of Sheet Metal CNC Incremental Forming Based On Closed-Loop Control

Sheet metal incremental forming process is a flexible process which is to form the sheet point by point on NC forming machine according to the prepared program.This technology is especially suited to develop small batch, diverse products, such as civil or automobile panels, which can greatly shorten the cycle of product development, reduce development cost and risk.The springback during the sheet metal incremental forming process has great negative impact on the shape and dimension accuracy. Part shape error due to springback is one of the most important manufacturing defect in sheet metal incremental forming process. In this paper,control science was introduced to the process of digital incremental forming for springback compensation .Aiming at springback error, a closed-loop accuracy control system for sheet metal digital incremental forming is constructed.With the discrete Fourier transform description of 3D surface and the system identification method,transform function of forming process is discussed. Due to some disadvantages of Fourier transform,such as its poor capability of describing local information of signal in the domain of time ,a closed-loop springback compensation algorithm which is focused in the combination of fast Fourier transform and wavelet transform is provided.Using this algorithm we can obtain the perfect tool-path curved surface and then we can adjust the forming surface of the tool-path in order to accomplish the precisely forming of sheet metal part.The proposed method was demonstrated for one case of forming a simple three dimensional spherical part.The result of the numerical investigation indicates that the designed tool-path curved surfaces are found to produce the target part shape with very small error only through three adjusting trials. So the closed-loop springback compensation algorithm for incremental forming is conclude to be effective.