Research On Variabl Blank Holder Force Control System For Drawing Forming Based On LabVIEW

Wrinkling instability and rupture instability are the two most common defects in deep drawing. Blank holder force(BHF) is one of the important parameters in sheet metal drawing process, The main function of the blank holder force is to produce the frictional resistance, in order to increase the tensile stress in the plate and control the flow of material, so that the sheet metal in the deep drawing is neither wrinkling, nor rupture.Taking the box drawing as an example, this paper mainly studies the control system of variable blank holder force and the related problems in the realization of the control of the mixed block blank holder force in drawing forming. Firstly, the corresponding edge pressing device is designed, the edge pressing ring along the circumferential direction is divided into straight side and corner, then the radial block is carried out in the corner.This method can be applied to different blank holder force. Then the electro-hydraulic proportional hydraulic system is designed, and the hydraulic cylinder is designed to act on the blank holder to realize the load of variable blank holder force in different regions.In order to realize closed loop control, the PID control theory is applied to the control system.The hydraulic system of the electro-hydraulic proportional linear processing,establish the core components of the system in mathematical modeling and the derivation of the transfer function.Then the closed-loop control system is simulated and analyzed.The step response curve of electro-hydraulic proportional hydraulic system is obtained,and the dynamic performance of the system is determined.Using LabVIEW software to develop the signal acquisition and real-time control program, then the human-computer interaction interface is designed, to achieve the signal acquisition and real-time control of the blank holder force.Using this control system for drawing experiment, the control error of the control system is analyzed by using the data collected from the experiment results, and the control system can satisfy the requirement of variable blank holder force control.At the same time, by comparing with other methods,the advantage of the method of mixing and blocking of box shaped parts is verified.