JPS6260210B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a control device for a machining gap in an electrical discharge machining apparatus that performs machining by applying pulsed discharge to the machining gap between an electrode and a workpiece. Conventional equipment controls the machining gap by comparing a signal proportional to the gap length, such as a voltage signal, with a reference voltage, and using the differential voltage to drive a drive device such as a motor to control the gap, and also by determining the gap signal to control the drive device. During machining, the drive device was kept in servo mode at all times. Therefore, the signal voltage in the gap always fluctuates depending on the behavior of machining debris generated in the machining gap, but the motor etc. that use this signal as a signal constantly rotates to servo the machining gap length to a varying degree. The gap length is adaptively controlled by this servo, but if it is controlled in response to the behavior of a small amount of machining debris as described above, this is unnecessary from the perspective of the entire machining gap. However, there were drawbacks that hindered stable machining.

In order to improve this drawback, the present invention performs machining by controlling the gap for a certain period of time and when the gap is in the optimum state, the gap control is stopped until the required repeated discharge is performed, and the required pulse discharge is repeated. After that, again,
The machining gap is controlled in steps so that the machining amount is corrected by controlling the gap, and the next pulse discharge is repeated at the corrected static gap.

The present invention will be described below with reference to an embodiment of the drawings. Reference numeral 1 represents a machining electrode, and 2 represents a workpiece, which face each other to form a machining gap. 3 is the processing power supply,
Machining pulses are generated by on/off control of a switch or by charging and discharging a capacitor, and are supplied to the machining gap. 4 is a motor of a driving device that controls the machining gap that changes depending on machining by servoing the electrode 1; 5 is a resistor that detects the average voltage of the machining gap that is proportional to the gap length of the machining gap; and 6 is the detection A discrimination circuit that compares the voltage with a standard value and outputs either a signal to narrow the machining gap or a signal to widen the machining gap, and both of these output signals are used to generate a signal that generates a servo drive signal. Add to circuit 7. The signal generating circuit 7 controls the motor 4 by outputting a drive signal for narrowing the gap or a drive signal for widening the gap in response to the signal from the discrimination circuit 6. The drive signal may be an analog quantity, but to explain digital pulses, the circuit 7 oscillates in response to the input signal and generates a pulse train of predetermined on-pulses and off-pulses, and each time one pulse signal is applied to the motor 4, If the motor 4 is a pulse motor or a DC motor with encoder control and is digitally fed, if the electrode 1 is set to be fed a predetermined constant distance, for example, in steps of 1μ, then the number of output pulses will vary depending on the number of output pulses. The predetermined distance is accurately fed. Reference numeral 8 indicates a resistor that detects the pulse by the voltage change, which generates electrical discharge in the machining gap due to the machining pulse supplied from the machining power supply 3, and 9 indicates a half circuit that discriminates the detection pulse signal. , a discharge pulse, or, for example, a discharge pulse, or a discharge pulse, for example, by selecting a discharge pulse discrimination reference level, a good discharge pulse or a bad discharge pulse is discriminated among the discharge pulses, but for now, it is assumed that the discharge pulse is discriminated. 10 is a preset counter that counts the discrimination output of the half-separated circuit 9;
Each time a predetermined count is performed, a signal is output and a time circuit 13 forming a control circuit is operated to maintain the signal for a predetermined time. For example, a one-shot multi is used as the time circuit, and a signal is applied to AND gates 11 and 12 during this operating time. Therefore, the signal generating circuit 7 generates a driving pulse during the operating time of the time circuit 13, and the gap control is not performed until the preset counter reaches the predetermined value again after the operating time of the time circuit 13 has elapsed. will be stopped. 1
4 is a detection resistor for the machining current, which detects a signal voltage proportional to the average machining current; 15 is a half-discrimination circuit that discriminates the detection signal in stages; and 16 is a preset value of the counter 10 that switches in response to the discrimination output. It is a switching device.

In electric discharge machining, machining pulses are supplied from the machining power supply 3 to the machining gap between the electrode 1 and the workpiece 2, and the pulse discharge is repeated to perform machining. Since the machining signal generating circuit 7 stops operating and does not generate a drive signal, the motor 4 stops, the electrode 1 stops, and pulse discharge is repeated in the static gap to proceed with machining. Therefore, as machining progresses, the machining gap gradually widens, making it difficult to start the discharge.Each discharge is detected by a resistor 8 and discriminated by a half-separate circuit 9, and the number of pulses is counted by a counter 1.
It is counted as 0. The counter 10 is preset to a predetermined value, and when it counts up to the preset number, it outputs a signal to activate the time circuit 13.

During the determined time of this time circuit, the gate 11,
12 signals are added. On the other hand, in the machining gap, a proportional signal voltage is constantly detected by the detection resistor 5, and as the gap length increases, the signal voltage also increases. This detection signal is discriminated by a half-separate circuit 6, and a signal is generated to narrow the gap that has widened as the machining progresses, and when the detection signal decreases due to a short circuit in the machining gap, etc. Generates a signal in the direction of widening the gap. The output of this half-separated circuit is always gate 11,
However, it is applied to the signal generating circuit 7 through the gates 11 and 12 only when the output signal of the time unit 13 is applied. Signal generation circuit 7
is generated by repeatedly generating a predetermined drive pulse signal in response to a signal in the direction of narrowing the gap corresponding to the output of the half-separated circuit 6, and drives the motor 4 to give a follow-up feed of 1μ/1p to the electrode 1. Control is performed to narrow the gap that has widened, and if a short circuit occurs, separate half circuit 6
A drive pulse signal is output in response to the signal in the direction of widening the gap between the outputs of Since the signal is inverted to narrow the gap, the pulse generated by the signal generating circuit 7 is also inverted to perform step follow-up control so as to narrow the gap. In this way, if the gap widened by processing is narrowed to a predetermined gap, the detection signal voltage will proportionally become a predetermined value.
The half-separated circuit 6 determines slight fluctuations above and below a predetermined value and outputs a signal, and the circuit 7 outputs a driving pulse, causing the motor 4 to repeat the seesaw servo and maintain a predetermined constant gap. . Then, when the time device 13 completes the predetermined operating time, the gate 1
1 and 12 are closed, the motor 4 is stopped, the machining gap is corrected to a predetermined gap, and the machining gap is stopped, and the next pulse discharge is repeated in the stationary gap, allowing the machining to proceed. In addition, during this gap correction control, machining debris generated and accumulated due to the previous repeated discharge,
Gas and the like are also removed by the movement of the electrode 1, and a cleaning operation is also performed, which has the effect of making the next pulse discharge stable.

The time device 13 is set so that the machining gap correction operation is completed at the end of the operating time, and the counter 10 is set so that the machining gap correction operation is completed when the operating time is completed, and the counter 10 is set so that the machining gap correction operation is completed before the machining progresses and the gap widens and electric discharge becomes difficult to occur. A preset value for counting discharge pulses is selected and set so that the gap can be corrected before stable machining becomes difficult due to the accumulation of
The machining gap is corrected every time the machine counts the preset value.

In addition, the preset of the counter 10 is naturally different for rough machining where the machining current is increased and for finishing machining where a small amount of machining is performed using single pulse discharge, and in electric discharge machining that performs optimal automatic control, the current value is It constantly changes depending on the state of the gap, and the preset value is automatically controlled accordingly. The machining current is detected by the resistor 14, and the switching device 16 is activated by the signal discriminated by the half-circuit 15. When activated, the presets of the counter 10 are automatically switched and controlled. When the machining current increases, the number of counter presets is decreased, and when the machining current decreases, the number of presets is increased. As a result, the machining gap correction control is performed at the optimum time, and stable machining can be continued by the gap step control. Note that the preset switching control of the counter 10 may be controlled based on changes in the machining area, and machining waste, gas, etc. generated by electric discharge increase in proportion to the number of discharge pulses, but when the machining area is large, the machining area is narrow. Since the area is less affected by contamination by machining debris and the like and inhibits normal discharge, the number of presets can be increased and the interval between gap corrections can be lengthened. It is also effective to perform this as the machining depth changes; as the machining depth increases, the removal effect of machining debris becomes worse, so the gap should be controlled at intervals where the discharge is not adversely affected. Decrease the number of counter presets so that

Note that the control circuit is not limited to the case where the time device 13 and the AND gates 11 and 12 control the half output of the half circuit 6 which is applied to the signal generation circuit 7; The drive signal may be controlled by a switch. In this case, the signal generating circuit 7 can be constantly operated to generate and output a drive signal corresponding to the signal from the half circuit 6.

With either method, the machining gap can be controlled by counting the number of machining pulses, discharge pulses, or the number of good discharge pulses and bad discharge pulses without having to constantly operate the drive device as in the conventional servo system. Since the gap is controlled each time the gap is corrected and the next pulse discharge is repeated with a stationary gap, stable machining can be achieved and machining efficiency can be improved.

[Brief explanation of the drawing]

The drawing is a circuit configuration diagram of an embodiment of the present invention. 1 is an electrode, 2 is a workpiece, 3 is a processing power source, 4
is the motor, 5, 8, 14 are signal detection resistors, 6,
9 and 15 are half-separate circuits, 7 is a signal generating circuit, 10 is a preset counter, 11 and 12 are AND gates, 13 is a time device, and 16 is a preset switching device.

Claims (1)

[Scope of Claims] 1. In an apparatus that performs electric discharge machining by supplying machining pulses from a machining power source while controlling a machining gap between an electrode and a workpiece using a servo drive device, a discrimination circuit that outputs a signal in the direction of narrowing or widening the machining gap; a signal generation circuit that outputs a drive signal to the servo drive device in response to the output signal of the discrimination circuit; a detection circuit for detecting pulses or discharge pulses; a counter for counting the number of pulses detected by the detection circuit; and a time period for applying a drive signal from the signal generation circuit to the servo drive device when the counter counts a set number. 1. A gap control device for an electrical discharge machining device, comprising: a time control circuit for setting time. 2. In a device that performs electrical discharge machining by supplying machining pulses from a machining power source while controlling the machining gap between an electrode and a workpiece using a servo drive device, the machining gap is controlled by a signal corresponding to the gap length of the machining gap. a discrimination circuit that outputs a signal in the direction of narrowing or a signal in the direction of widening; a signal generation circuit that outputs a drive signal to the servo drive device in response to the output signal of the discrimination circuit; and a machining pulse or discharge for the machining gap. a detection circuit that detects pulses, a counter that counts the number of pulses detected by the detection circuit, and a time that sets a time for applying a drive signal from the signal generation circuit to the servo drive device when the counter counts a set number. A gap control device for an electric discharge machining apparatus, comprising: a control circuit; and a switching device for switching the count setting number of the counter. 3 The signal generation circuit generates a digital pulse train signal, and the servo drive device
A gap control device for an electric discharge machining apparatus according to claim 1, characterized in that the device performs pulse feeding control over a predetermined minute distance per pulse. 4 The signal generation circuit generates a digital pulse train signal, and the servo drive device
A gap control device for an electric discharge machining apparatus according to claim 2, characterized in that the device performs pulse feeding control over a predetermined minute distance per pulse. 5 The detection circuit detects a good discharge pulse among the discharge pulses,
The gap control device for an electric discharge machining apparatus according to claim 1, wherein the gap control device is configured to discriminately detect a defective electric discharge pulse. 6 The detection circuit detects a good discharge pulse among the discharge pulses,
The gap control device for an electric discharge machining apparatus according to claim 2, wherein the gap control device is configured to discriminately detect a defective electric discharge pulse. 7. The gap control device for an electric discharge machining apparatus according to claim 2, wherein the switching device automatically switches the set count number depending on the discharge current value, machining area, or machining depth.