Abstract: EDM apparatus has a servo drive under the control of a main control system for advancing a machining electrode toward a conductive workpiece. When the electrode arrives at a surface of the workpiece to commence EDM machining, the main control system causes a sudden deceleration of the servo. The depth controller detects this sudden deceleration by means of a sensor and sets a zero reference plane from which machining depth is measured. The depth controller can also detect electrode breakthrough by detecting servo acceleration occurring when the electrode breaks through a surface of the workpiece.

Abstract: A process control system for electrical discharge machining apparatus to control automatically the machining of a workpiece. The process control system is operable to receive and retain a plurality of operation instructions regarding electrical discharge machining parameters and transmit operation commands to the electrical discharge machining apparatus to execute the operation instructions in controlling the complete machining of a workpiece. The process control means includes a storage unit operable to store a plurality of operation instructions enabling absolute repeatability of the machining process defined by the operation instructions in the storage unit for a plurality of workpieces. The process control system also includes a digitally controlled servo system to regulate the movement of the electrode toward and away from the workpiece.