Control system of a mini hydraulic press for evaluating springback in sheet metal forming

The paper proposes a method of evaluating springback that occurs after unloading during sheet metal forming of a control system. A linear displacement occurring by springback of the components formed is used as the reference value of springback to evaluate actual springback, and displayed on the control interface in real time. The proposed method is based on measurements performed during closed loop controlled stamping operations. To perform the close-loop control of the hydraulic press two pressure sensors are installed in the cylinder chambers and a position sensor (optical scale with a resolution of I mu m) is installed on slip rod of punch. Both control and monitoring software run on a real-time hardware board that is directly programmed through the Matlab/Simulink environment. The data of the hydraulic force and punch position, as also the springback effects, can be shown on the control/monitoring interface in real time during stamping process. For the work, an experimental example is used to build and test the control system on a mini-press (1), and a linear model was provided to test the strategy to control the punch position and/or force. Hardware-in-the-loop simulation techniques are also used in experiments to verify the control of overall system. System models possess the characteristics of less computing power and adjusting parameters easily. The punch position can be controlled with high precision in a moving travel of 200 mm. The purpose of the work is to offer an effective way for evaluating springback in real time during sheet metal forming. (c) 2006 Elsevier B.V. All rights reserved.