Development of sheet metal active-pressurized hydrodynamic deep drawing system and its applications

An active-pressurized hydrodynamic deep drawing (AHDD) system applying closed-loop control to regulate cavity pressure and blank holding force (BHF) independently in real time was developed to realize various loading paths for manufacturing complex parts. The conventional passive-pressurized hydrodynamic deep drawing (PHDD) method generates pressure by compressing liquid as the punch drawing into the die cavity, which is an open-loop controlling system and provides large control error. Proposed AHDD system consists of mainframe, hydraulic control system and real-time control system based on upper and lower computers. In order to obtain higher control precision, the PID controllers with error judgment were employed. Meanwhile, the punch speed was controlled according to real-time detection of errors between desired value and measured value to restrict control errors to a limited scope. Furthermore, the process experiments were carried out on the developed AHDD system, and the effects of control strategies on the formability of the parts were investigated. The qualified parts without tears and wrinkling were manufactured integrally on the AHDD system using PID controllers possessing error detection. The results indicated that the AHDD system offers multiple loading paths of BHF and cavity pressure, which is propitious to form complicated structural components and high-strength materials, and the proposed PID control strategy can improve the formability and uniformity of wall thickness distributions of the workpieces.