Investigations on a directly coupled piezoactuated tool feed system for micro-electro-discharge machine

A directly coupled piezoactuated tool feed mechanism is proposed and a prototype micro-electro-discharge machine (micro-EDM) is developed. The piezoactuator is used to feed the tool and also to sense the tool displacement from a reference position. The hysteresis behavior of the piezoactuator is also incorporated through an electromechanical model for estimating the actual tool displacement. Simulation results for piezoactuator displacement are compared with the experiment and a maximum error of 15% was observed. Further, in order to control the tool feed rate during machining, a tool feed controller based on the gap voltage feedback is developed. A contact-based measurement technique is integrated with the tool feed controller to measure the tool wear and the depth of material removed. Micromachining experiments have been conducted on a copper workpiece with copper and tungsten as tool materials. The experimental results obtained through the contact-based measurement technique are in agreement with the tool-displacement simulations with a maximum error of about 10%.