Integration of an Electrical Discharge Machining module onto a Reconfigurable Machine Tool

Abstract

The objective of this research was to integrate an Electrical Discharge Machining module onto an existing reconfigurable CNC machine tool, using a modular approach, which potentially would enable conventional milling and EDM to be conducted in a co-ordinated fashion on the same machine tool. Ideally, multi-axis EDM is desired; however, single axis investigations were first done, as a step towards this ideal. The investigations determined which possible integration options should be pursued. This paper considers these single-axis investigations. The integration strategies implemented and evaluated in this research were (a) using the EDM machine's servo-drive output to drive the Reconfigurable Machine Tool's Z axis servo motor, via an external amplifier, (b) using a control signal from the EDM machine to communicate with the PC-based CNC control program (Mach3) to achieve advancement and retraction of the electrode using the RMT's Z axis servo motor, but governed by the EDM process, and (c) using an external controller, effectively replacing the EDM machine's controller and the CNC controller, while providing actuation of the electrode by means of a moving coil linear actuator mounted on the (now fixed) Z axis of the CNC machine. The external controller was implemented in LabVIEW, using a data acquisition device. The third strategy required that a voltage monitoring circuit be implemented to sense conditions at the EDM process spark gap. Single axis EDM was implemented using this method, but a version of the controller for potential 2-dimensional machining was also developed. PC simulation models of the linear actuator, controller, and EDM process were produced.