JPS6010852B2 - Servo device for electrical processing - 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 electric discharge machining.

Conventionally, devices have been proposed that control the gap by determining the detection voltage of the machining gap and applying the digital pulse directly or via a logic circuit to a servo drive body such as a motor to control the gap. However, electrical processing requires water,
Machining is performed by supplying a machining fluid such as oil to a machining gap, and when the fluid resistance changes during machining, a detection signal such as a gap voltage changes, which is used as a servo signal. However, there was a drawback that a constant gap length and gap width could not be maintained at all times. The present invention has been proposed to eliminate this drawback, and allows manual or automatic correction of the servo signal by detecting the resistance value of the machining fluid supplied to, intervening in, or flowing through the machining gap. It was designed to do so.

The present invention will be explained below with reference to an embodiment of the drawings.

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 electric discharge machining is performed by pulsed discharge.

2, 3, and 4 are discrimination circuits that discriminate and check repeated pulse discharges in the machining gap, 2 discriminates abnormal discharge (DAME), 3 discriminates unexploded discharge (OPEN), and 4 discriminates good discharge (DAME).
OK).

The determination is made by detecting the gap voltage, and if the discharge is good, the gap voltage is higher than a predetermined value, and the discharge is an arc. When an abnormal discharge occurs due to a short circuit, the voltage drops significantly, so it can be easily and accurately determined by Schmitt et al. Also, if no discharge occurs even when a pulse voltage is applied from the power supply, there is no voltage drop and the power supply voltage is maintained. can be easily identified. 5, 6,
A preset counter 7 counts the output of each of the discrimination circuits 2, 3, and 4, and outputs a signal when it continuously counts up to the preset number.

The optimum values are selected and set for the presets of the counters 5, 6, and 7 by automatic switching by switchers 8, 9, and 1 provided respectively.

Reference numeral 11 denotes a circuit for detecting the gap machining fluid resistance, and this detection signal is discriminated by a discrimination circuit I2, and the discrimination is made by discriminating the detection resistance into a plurality of stages, and each switch 8, 9, 10 is actuated by the discrimination output. Switch and select counter preset values by automatic control.

The counters 5 and 6 output a signal when counting the preset number, but NAND gates 14 and 15 are inserted so that the signal does not advance unless the signal from the time device 13 is added.

The time unit 13 outputs a time signal at a frequency lower than the response frequency of the servo drive. Each counter 5, 6 is cleared by the respective output and the NAND gate output of the time signal, and is also cleared by the output of the counter 7 which counts the OK signal. 16 is a servo signal generation circuit that outputs an UP signal every time a signal is applied from the gate 14, and 17 is a servo signal generation circuit that outputs a DOWN signal every time a signal is applied from the gate 15. Drive control of the servo drive body 18 is performed, and servo control is performed in which the gap is widened by the up (U) signal, and the gap is narrowed by the down (D) signal.

It is well known that when machining is performed by repeatedly applying pulsed discharges to the machining gap 1, the state of occurrence of each discharge differs depending on changes in the state of the machining gap.

If the gap length is too wide, no discharge will occur; if it is too narrow, an arc will occur. If a short circuit occurs or a machining shoulder accumulates even if the gap length is appropriate, arc discharge will occur through it, and each discharge will change. Such a discharge state is checked by discriminating circuits 2, 3, and 4, respectively, and arc. Abnormal discharges (DAME) such as short circuits are determined by the discrimination circuit 2 and counted by the counter 5, and unexploded discharges (OPEN) are detected by the discrimination circuit 3.
A good discharge (OK) is determined by the determination circuit 4 and counted by the counter 7, and each counter 5
, 6, and 7 do not output a signal until the preset number is counted, and they output a signal to determine whether the discharge pulse train is good or bad based on the number of consecutive discharge pulse trains. is not output. When many good discharges occur in the discharge pulse train, the gap is normal and the counter 7 rapidly counts and reaches the preset number and outputs it, which clears the other counters 5 and 6 and outputs the signal. (No, the servo drive body 18 remains stopped) and machining continues. If the number of abnormal discharges increases, counter 5
The up signal generating circuit 16 is activated by the output of the gate 1, but while the time signal is not applied from the time device 13, the gate
4, the signal is stopped, and when a predetermined time elapses and a signal is output from the time device 13, the circuit 16 is activated and outputs an up signal to control the drive body 18 up, that is, to widen the gap.

In addition, if the number of misfired discharges is large, the counter 6 rapidly counts up to the preset value and outputs a signal. Control is performed to drive 18 to narrow the gap.Time device 1
The time signal No. 3 is set to a gap and frequency that the drive body 18 sufficiently responds to, and the drive body 18 always responds faithfully to the signal by the outputs of the control circuits 16 and 17, and is always stabilized by highly accurate gap control. processing can be carried out. However, as described above, the machining fluid resistance changes during machining.

The changes are particularly large in processes that use water (distilled water). Controlling the liquid resistance to a constant level requires complicated and expensive mechanisms. As described above, if this change in liquid resistance is ignored, the machining gap will not be maintained optimally even if the discharge state of the gap is determined, the servo signal is generated, and the servo is performed by controlling the driver. Therefore, the liquid resistance in the gap is constantly detected by the detection circuit 11.

The detection signal is discriminated by a discrimination circuit 12 and discriminated into multiple stages. Based on this determination, the switching devices 8, 9, and 1 select the preset of the counters 5, 6, and 7. For example, when the liquid resistance is high, abnormal discharge is unlikely to occur, so the DAM
Set the E pulse counter 5 preset to 4. Also, since it will be difficult to generate a discharge, set the OPEN pulse counter 6 to 4.
When the preset is set large and the liquid resistance decreases,
Since abnormal discharge is likely to occur, the preset of the counter 5 is set large in this case, and the preset of the counter 6 is set small because the discharge is easy to occur. As an experimental example, pulse 7 of the processing pulse.

In an example in which iron material was machined using a copper electrode using the N250 French S, an extremely optimal servo was achieved when the following counter preset was performed. Liquid resistance (Q skin) 106~1
2 5 x 105 4 x 104 103 Counter 5 preset number 3 5 8 136 〃 6
5 3 27″ 14 18 2
2.28 By switching and changing the counter preset in response to changes in liquid resistance as described above, it is possible to control the optimum machining gap, and even when liquid resistance changes, stable and accurate machining is achieved with a stable servo. can be done.

This may also change the liquid resistance during machining, which is particularly effective in machining that uses water. Furthermore, the above is
Although the present invention has been explained by way of one embodiment, abnormal discharge (DA)
ME), misfire discharges (OPEN), and good discharges (OK) may be counted individually and used as servo signals, or such abnormal discharges, misfire discharges, good discharges, etc. can be counted continuously and the consecutive number can be used as a servo signal. In addition to using an up/down counter as a signal, measure the ratio of good discharge, abnormal discharge, etc. to the total number of discharges in repeated discharges, or the relative ratio between good discharge, abnormal discharge, misfire discharge, etc. It may also be used as a generation signal for a servo signal.

In either case, the servo control signal switches and selects the preset of the counter using changes in machining fluid resistance as a signal, so a stable and constant machining gap can be maintained at all times, allowing stable and highly accurate machining. Note that the counter preset switching may be performed manually according to a certain standard.

[Brief explanation of drawings]

The drawing is a configuration diagram of an embodiment of the present invention. 1 is a machining gap, 2, 3, and 4 are discrimination circuits, 5, 6, and 7 are counters, 8, 9, and 10' slivers, 11 is a liquid resistance detection circuit, 12 is a discrimination circuit, 13 is a time device, 14 and 15 are gates, 16 and 17 are servo signal generation circuits, and 18 is a driver.

Claims (1)

[Claims] 1. A discriminator is installed to check and distinguish the discharge state that repeatedly occurs in the machining gap, distinguishing between unexploded discharge (OPEN), good discharge (OK), or abnormal discharge (DAME), and one or more of these discharge states A counter that counts the consecutive number, overall number ratio, or relative number ratio, and a circuit device that outputs up/down digital servo signals based on the output of the counter are provided, and the up/down servo signals are added to the servo drive body for processing. In a device that digitally servo feeds an electrode or a workpiece that forms a gap, a device that detects the resistance value of a machining fluid that is supplied to, intervenes in, or flows through the machining gap, and a determination that determines the detection signal of the device. A servo device for electrical machining, characterized in that the preset value of the counter is changed and set manually by displaying the discrimination output or automatically by displaying the discrimination output.