Abstract: A wire feed protection system for an electrical discharge machining apparatus and machine tool. The workpiece is supported for movement along two coordinate axes in the "X" and "Y" direction through electrically controlled stepping motors in a manner which is well known to the art. The electrode is of a wire or band configuration and is so supported, guided, and driven that the cutting portion of the electrode which is aligned with the workpiece before and during cutting remains properly oriented and travels without bend or distortion in its path. When the wire breaks, bows or otherwise is caused to lose tension, a switch is operated to interrupt machining power pulses being supplied to the machining gap. For this purpose, a switch is located at one or more critical and predetermined locations in the wire electrode path, with the switch actuator in each case in engagement with the wire during transversal.

Abstract: The system includes data input means for information relative to the material of the workpiece and the thickness of the workpiece. A read-only memory then provides information to a programmable counter so that off-time for the machining power pulses is appropriately provided for. In addition, there is manual preset means for setting the off-time to be provided during gap short circuit condition. An appropriate cut-off sensing circuit is operatively connected to the gap for sensing short circuit condition and initiating the pulse reduction but only for the duration of the gap short circuit condition.

Abstract: A power supply circuit particularly useful in a multiple gap or a multiple electrode system in which multiple electrodes and a common workpiece or multiple electrodes and a like number of workpieces are selectively connected in circuit with a common DC source power supply circuit. A switching system is further provided for reversing the polarity of electrode relative to workpiece. A power supply circuit itself incorporates a specialized push-pull drive stage effective to drive the output stages in either polarity setting in such manner as to allow for negligible noise in the system. The drive system is one which generates triggering pulses effective to switch the output transistor bank in either polarity very rapidly and independently of the number of output leads which may be included.

Abstract: The system includes a pair of stepping motors for controlling relative movement of the wire electrode relative to the workpiece with the velocity of movement being controlled as a function of gap voltage. For this purpose the system includes a voltage controlled oscillator having its input coupled to the machining gap and its output interconnected with the drive circuits for the two stepping motors. The system further includes a divider stage which becomes operable in the system responsive to drop of voltage indicating gap short circuit condition so that a drastically reduced number of stepping pulses are provided to the motors throughout the duration of the gap short circuit condition. After removal of the gap short circuit condition, an increase in voltage allows changeover through several different gating stages to again return the output of the voltage controlled oscillator to its normal frequency range so that the feed of the electrode relative to the workpiece is again continued.

Abstract: Included in the circuit are a pulse generator and an electronic output switch for providing machining power pulses across the EDM gap. The circuit includes an opti-coupling system intermediate the pulse generator and the output switch to pass triggering pulses to control the conduction of such switch. The opti-coupling system includes a light emitting device operably coupled to a light responsive device for controlling the triggering pulses passed to the output switch. In a further embodiment, a multiple gap set-up includes a single pulse generator for triggering pulses and a plurality of machining gaps, each having a separate opti-coupling system between the pulse generator and the associated gap.