Abstract:  An NC system based on PC and PMAC (Programmable Multi-Axis Controller) was constructed for EDM mill to meet the need of adjusting velocity and direction of movement relying on gap statement in the process. According to real-time requirements, system tasks were assigned to PC and PMAC. This improved system real-time feature and reliability. A couple of motion NC programs for same track with different directions were generated combined with PLC program to realize the backward movement of EDM mill. According to machine gap status, the time based function of PMAC was used to control electrode motion velocity. The direction and velocity of track movement were totally controlled by PMAC. This reduces   computing burden of the host PC and improves the real time feature of the processing. 3D cavities were machined to prove the effectiveness of the methods developed in this paper.

Key words: electrical discharge milling(EDM), servo control, time based function, programmable multi-axis controller(PMAC)