Method and apparatus for controlling electric discharge machine

A method of controlling an electric discharge machine wherein a motor, for establishing relative movement between an energized electrode and a workpiece, is driven in accordance with command data in order to machine the workpiece to a desired shape by an electric discharge produced between the electrode and workpiece, the electric discharge machine including a memory, counting means and a sensor, said method comprising the steps of:

• (a) entering the command data;
• (b) storing in the memory retraction control information contained in the entered command data;
• (c) moving the electrode in an advancing direction relative to the workpiece by controlling the speed of the motor in accordance with machining feed speed information contained in the entered command data;
• (d) monitoring the current position of the electrode by counting, via the counting means, sensor pulses generated by the sensor whenever the motor rotates by a predetermined amount, comprising the steps of:
• (di) counting, via the counting means, the sensor pulses generated by the sensor each time said motor rotates by a predetermined amount;
• (dii) reading the value of the count in the counting means at predetermined intervals;
• (diii) adding said read counted values cumulatively at said predetermined intervals to determine the present position of the electrode;
• and
• (div) sending a cancel command to the counting means each time its counted value is read, thereby to cancel said counted value;
• (e) moving the electrode in a retracting direction relative to the workpiece by reading in a retraction speed from the retraction control information stored in the memory and controlling the speed of the motor on the basis of the retraction speed, when a signal indicative of a short circuit is generated;
• and
• (f) moving the electrode in the advancing direction relative to the workpiece by reading in a readvancing speed from the retraction control information stored in the memory, when a signal indicative of an end to the short circuit is generated.

A method of controlling an electric discharge machine wherein a motor, for establishing relative movement between an energized electrode and a workpiece, is driven in accordance with command data in order to machine the workpiece to a desired shape by an electric discharge produced between the electrode and workpiece, the electric discharge machine including a memory, counting means and a sensor, said method comprising the steps of:

• (a) entering the command data;
• (b) storing in the memory retraction control information contained in the entered command data;
• (c) moving the electrode in an advancing direction relative to the workpiece by controlling the speed of the motor in accordance with machining feed speed information contained in the entered command data;
• (d) monitoring the current position of the electrode by counting, via the counting means, sensor pulses generated by the sensor whenever the motor rotates by a predetermined amount;
• (e) moving the electrode in a retracting direction relative to the workpiece by reading in a retraction speed from the retraction control information stored in the memory and controlling the speed of the motor on the basis of the retraction speed, when a signal indicative of a short circuit is generated;
• (f) moving the electrode in the advancing direction relative to the workpiece by reading in a readvancing speed from the retraction control information stored in the memory, when a signal indicative of an end to the short circuit is generated;
• and
• (g) controlling the relative movement of the electrode in the advancing direction by comparing the current position of the electrode, found in step (d), with positional information contained in said command data.

An apparatus for controlling an electric discharge machine wherein a motor for establishing relative movement between an energized electrode and a workpiece is driven in accordance with command data in order to machine the workpiece to a desired shape by an electric discharge produced between the electrode and workpiece, said apparatus comprising:

• a memory for storing retraction control information contained in entered command data;
• a driving circuit, connected to the motor, for driving the motor in accordance with the magnitude of a given speed command;
• a sensor, coupled to the motor, for generating a pulse whenever the motor rotates by a predetermined amount;
• movement monitoring means, connected to said sensor, for monitoring the current position of the electrode on the basis of a value obtained from the number of pulses generated by said sensor;
• and
• control means, connected to said memory, and between said driving circuit and said movement monitoring means, for applying machining feed speed information contained in the command data to said driving circuit, for reading in and applying to said driving circuit, when a signal indicative of a short circuit is generated, retraction speed information contained in the retraction control information stored in said memory, and for reading in and applying to said driving circuit, when a signal indicative of an end to the short circuit is generated, re-advancing speed information contained in the retraction control information stored in said memory.

An apparatus for controlling an electric discharge machine wherein a motor for establishing relative movement between an energized electrode and a workpiece is driven in accordance with command data in order to machine the workpiece to a desired shape by an electric discharge produced between the electrode and workpiece, said apparatus comprising:

• a memory for storing retraction control information contained in entered command data;
• a driving circuit, operatively connected to the motor, for driving the motor in accordance with the magnitude of a given speed command;
• a sensor, coupled to the motor, for generating a pulse whenever the motor rotates by a predetermined amount;
• movement monitoring means, operatively connected to said sensor, for monitoring the current position of the electrode on the basis of a value obtained from the number of pulses generated by said sensor;
• control means, operatively connected to said memory, said driving circuit and said movement monitoring means, for applying machining feed speed information contained in the command data to said driving circuit, for reading in and applying to said driving circuit, when a signal indicative of a short circuit is generated, retraction speed information contained in the retraction control information stored in said memory, and for reading in and applying to said driving circuit, when a signal indicative of an end to the short circuit is generated, re-advancing speed information contained in the retraction control information stored in said memory;
• and
• counting means, operatively connected to said movement monitoring means and said sensor, for counting the pulses generated by said sensor.