JPS6113934B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement of a machining gap servo device in an electric machining machine such as an electric discharge machining machine.

Conventionally, a device has been proposed that detects and discriminates the voltage of the machining gap for each applied voltage pulse, controls the digital pulse by applying it to a servo drive body such as a motor as a servo signal, and sends it to the electrode to control the gap. However, the repetition frequency of electric discharge in electric discharge machining is extremely high, and the servo drive body has inertia, etc., and cannot sufficiently follow the servo signal of the digital pulse. Also, even if the gap in the machining gap is normal, it may sometimes cause arcing or
Abnormal electrical discharges due to short circuits occur, but if these were detected one by one and the gaps were controlled, the gaps would constantly widen or narrow, making stable machining impossible.

The present invention has been proposed in view of the above-mentioned conventional problems, and is characterized by a discriminator that discriminates the state of discharge based on voltage pulses repeatedly applied to the machining gap, and detects unexploded discharges ( OPEN)
Distinguish between abnormal discharge (DAME) or good discharge (OK). and a discharge state signal output circuit that counts the discrimination outputs related to these discriminated discharge states and outputs a signal when the counted number reaches a preset number, and a frequency corresponding to the maximum self-starting frequency of the servo drive body. a time device that outputs a signal; and an AND combination signal of the output signal of the time device and the output signal from the discharge state signal output circuit to output up and down digital servo signals to control the servo drive body and control the servo drive. That's what I decided to do.

This will be explained below using an example diagram. Reference numeral 1 denotes a machining gap formed between a machining electrode and a workpiece, to which a machining pulse power source (not shown) is connected, and electrical discharge machining is performed by a pulse discharge generated by an applied voltage pulse. 2 and 3 are discrimination circuits that discriminate the state of discharge based on voltage pulses repeatedly applied to the machining gap, 2 discriminates abnormal discharge (DAME), and 3 discriminates unexploded state (OPEN). Discrimination is done by detecting the gap voltage, and if it becomes an abnormal discharge due to an arc or short circuit, the voltage will drop significantly, so it can be easily and accurately determined by Schmitt etc. Also, if no discharge occurs even if a voltage pulse is applied from the power supply. This can be easily determined because there is no voltage drop and the power supply voltage is maintained. 4 and 5 are preset counters that count the discrimination outputs of the respective discrimination circuits 2 and 3, and output a signal when they continuously count up to the preset number. The preset number of each counter 4, 5 is given by a switch 6, 7 provided for each counter, and is used for rough machining, finishing machining, low electrode consumable machining, consumable machining, material combination of electrode and workpiece,
The electrical processing conditions (pulse width, pause width, repetition frequency, etc.) of the processing pulse power source are switched and controlled by these processing conditions, so the number of presets can be changed in response to the switching change of the power supply. change. Each counter 4, 5 outputs a signal when it completes counting the preset number, but NAND gates 9, 10 are inserted so that the signal does not proceed to the next stage unless the time signal from the time device 8 is added.
Further, each counter 4, 5 is connected to a delay circuit 16, 17 when the time device 8 outputs a time signal, which will be described later.
is input to the reset terminal of each counter 4, 5 through the counter 4, 5, the count number of the counter 4, 5 up to that point is cleared, and re-counting is started. 17 and other input/output circuits constitute a discharge state signal output circuit. The time device 8 outputs a signal having a time interval corresponding to approximately one cycle of the maximum self-starting frequency of a servo drive body (such as a motor), that is, a signal having a frequency corresponding to the maximum self-starting frequency. Note that the maximum self-starting frequency in the present invention means approximately the maximum frequency among the self-starting frequencies under machining load conditions. 11 is a servo signal generation circuit that outputs an UP signal every time a signal is applied from gate 9, and 12 is a servo signal generation circuit that outputs a DOWN signal every time a signal is applied from gate 10. Drive control of the servo drive body 13 is performed, and servo control is performed to widen the gap in response to an UP signal and to narrow the gap in response to a DOWN signal. 14 is counter 4
A preset counter 15 counts the output pulses of the counter 14, and 15 is a circuit that generates a reciprocating control signal based on the output signal of the counter 14. This output drives the driving body 13 to perform a reciprocating motion with a long stroke that widens the gap and then narrows it. By doing this, a pumping action for inflowing and discharging the surrounding machining fluid is activated, thereby cleaning the machining gap. This cleaning cycle is controlled by the preset number of the counter 14 at intervals that allow optimum machining to continue.

In the above, when a voltage pulse of the machining condition selected and set is repeatedly applied to the machining gap 1 from the machining pulse power supply, and machining is performed by the generated pulse discharge, each application is applied depending on the state change of the machining gap. It is known that the states in which discharge occurs based on voltage pulses are different. If the gap length is too wide, no discharge will occur, if it is too narrow, an arc or short circuit will occur, and even if the gap length is appropriate, if machining debris accumulates, arc discharge will occur through it. The state in which discharge occurs due to the applied voltage pulse changes. These discharge states are determined by the discrimination circuits 2 and 3, and abnormal discharges such as arcs and short circuits (DAME) are discriminated by the discrimination circuit 2 and counted by the counter 4, and unexploded discharges (OPEN) are detected by the discrimination circuit. 3 and counted by counter 5. Each counter does not output a signal until it has counted up to the preset number, and the discharge state is determined by whether or not the number of discrimination output signals that determine the occurrence and state of discharge based on the applied voltage pulse can be counted up to the preset number. Outputs a judgment as to whether it is good or bad. Therefore, even if the machining gap is normal, defective discharges may occur due to the influence of machining debris, etc., or accidents such as failure to leave the machining gap can be performed to control the gap and eliminate defects that impede stable machining. can.

The up signal generation circuit 11 is operated by the output of each count 4 and 5, that is, by the output of the counter 4 that counts one abnormal discharge (DAME), but while the time signal from the time device 8 is not output, The signal is stopped at the gate 9 stage, and when the time signal is output from the time device 8 after a predetermined time has elapsed, the signal is applied to the circuit 11, which outputs an up servo signal to drive the driver 13 and perform up control, that is, widen the gap. Control. At this time, the counter 4 is cleared by adding the time signal from the time unit 8 delayed by the delay circuit 16, and starts counting again from the beginning. Also, if the time signal is output from the time device 8 before the counter 4 has counted up to the preset number, the counter 4 will clear the previous count before outputting the signal. Since the number of abnormal discharges (DAME) is small compared to, for example, the number of applied voltage pulses, the number of discharge pulses, or the number of unfired discharges, and the gap is considered to be normal, no servo signal is generated from the circuit 11, and the driver 1
3 is not controlled. On the other hand, if the number of unfired discharges (OPEN) is large, the counter 5 rapidly counts up to the preset number and outputs a signal, and when the time signal is added from the time device 8, a signal is applied to the circuit 12 from the gate 10 (DOWN). Control is performed to narrow the gap by generating a servo signal and driving the driving body 13. Furthermore, if a time signal is applied before the counter 5 has counted up to the preset number, it will be cleared at that point and no control will be performed to narrow the gap. During the voltage pulse applied to the machining gap in this way, before the cumulative count of the discrimination output from the other discrimination circuit reaches a preset number, the cumulative count of the discrimination output from one discrimination circuit reaches the predetermined preset number. Since one of the counters corresponding to one of the discrimination circuits is configured to output a signal only when the preset number of The optimum number of presets suitable for the machining conditions can be made, and the presets are adjusted so that stable machining can be continued through optimal machining gap control.

Therefore, the time signal of the time device 8 is
The frequency is set to approximately the maximum frequency among the self-starting frequencies that respond with sufficient precision, and at least at intervals of one cycle of this frequency,
Since an UP or DOWN servo signal is applied to the driving body, the driving body 13 faithfully responds to the signal, and stable machining can always be performed by highly accurate interval control. Furthermore, by controlling the servo signal at the maximum self-starting frequency, it is possible to quickly respond to changes in the discharge state and perform appropriate gap control.

In addition, the counter 14 counts the output of the counter 4 that counts abnormal discharge (DAME), and when the count reaches the preset number, a reciprocating signal is output from the circuit 15, and the driving body 13 is moved reciprocally to remove machining waste and close the gap. Perform cleaning.

Although the present invention has been described above by way of one embodiment,
To determine the discharge state of the machining gap, in addition to the combination of abnormal discharge (DAME) and unexploded discharge (OPEN), it is necessary to distinguish between one of these and, for example, a good discharge (OK), and use the discrimination output. It is also possible to count such abnormal discharges, good discharges, misfiring discharges, etc., and output a signal as a servo signal when the count reaches a preset number. In addition to outputting a discharge status signal and using it as a servo signal when the count number reaches a preset number, it is also possible to output a discharge status signal as a servo signal. Ratio, Matara discharge,
The ratio between the counts of abnormal discharge, misfiring discharge, etc. may be set by each preset number to output the discharge state signal and generate the servo signal. In either case, the servo control signal is controlled by the output signal of the time device with a signal of a frequency corresponding to the maximum self-starting frequency of the servo drive, so that the drive always operates in response to the input signal. It has the effect of enabling faithful control, stable gap control, and stable machining.

[Brief explanation of the drawing]

The drawing is a circuit configuration diagram of an embodiment of the present invention. 1... Machining gap, 2, 3... Discrimination circuit, 4, 5
... Counter, 8 ... Time device, 9, 10 ... NAND gate, 11, 12 ... Servo control signal generation circuit, 13 ... Servo drive body.

Claims (1)

[Claims] 1 Depending on the discharge state of the machining gap, when the electrode or workpiece that forms the machining gap is digitally servo fed by a servo drive, the state of discharge based on the voltage pulse repeatedly applied to the machining gap is determined. A discriminating device is provided to discriminate between unfired discharge and abnormal discharge by dividing the discharge states into halves, and each discharge state signal output unit counts the discrimination outputs related to these discriminated discharge states and outputs a signal when the counted number reaches a preset number. a circuit, a time device that outputs a signal with a frequency corresponding to the maximum self-starting frequency of the servo drive body, and an AND combination signal of the output signal of the time device and each output signal from the discharge state signal output circuit. A circuit device that outputs up and down digital servo signals is provided, and the up and down digital servo signals are provided.
A servo device for electrical processing, characterized in that a down digital servo signal is applied to a servo drive body.