Improving reciprocating traveling WEDM performance by a new adaptive servo feedrate control system

Abstract

With variations in gap discharge state or workpiece height, the servo feedrate of wire electrical discharge machining (WEDM) often fluctuates, and the machining process easily becomes unstable, thereby resulting in a decrease in material removal rate or an increase in risk of unexpected wire breakage. With developments of ISO-pulse discharge pulse power supplies and reciprocating traveling WEDM, a precise discharge state monitoring system for the servo federate control system is required. In this paper, with each single discharge pulse being precisely classified and counted, more accurate feedback information can be provided to the servo feedrate control system. Then a new adaptive servo feedrate control system with a self-tuning regulator and a variable gain linear proportional controller has been proposed to improve the material removal rate and control performance. The scheme of an adaptive servo feedrate control system is analyzed. It is found that the new adaptive servo feedrate control system by using a variable gain linear proportional component has a better control performance. By adjusting servo parameters, the discharge ratios are regulated, and the servo feedrate control system can keep the gap discharge state stable. Experimental results show that the material removal rate can be improved significantly by up to 19% with the new adaptive servo feedrate control system, without sacrificing the surface quality.