Workpiece height estimation in wire electrical discharge machining by using support vector regression

The risk of wire breakage adversely affects the full potential of wire electrical discharge machining since the overall process efficiency is considerably deteriorated. Online estimation of workpiece height can avoid wire breakage effectively as the estimated height can provide a reference for setting machining parameters so as to improve the machining speed and stability. In this article, a discharge frequency monitoring system based on voltage waveforms of wire electrical discharge machining is developed, and support vector regression is used to build up a model for online estimation of workpiece heights in wire electrical discharge machining. Experimental results show that besides at stairs of a workpiece where the value of estimation errors can reach up to 6 mm due to the poor flushing condition in machining, the developed model can successfully estimate the workpiece height with an estimation error of less than 2 mm. Based on the estimated workpiece height, the discharge frequency can be controlled at an optimal value without the risk of wire breakage when cutting a workpiece with a variable height.