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

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.