JPS6190825A - Electric discharge machine - Google Patents

Abstract

PURPOSE:To prevent fire and submergence of electrode holder into oil by controlling the volume of working liquid on the basis of a signal produced through decision of the optimal height of working liquid level obtained by adding specific height of working liquid level to the detected height of work. CONSTITUTION:Upon gradual motion of spindle 31 to contact an electrode 10 with a work 14, the output signal from a detector 19 will go to O level while upon transmission of the variation of signal level to NC machine 40, motion of the spindle 31 is stopped while simultaneously production of pulse from pulse generator 50 is stopped. Consequently, when counting the number of pulses produced from start to stop of the motion of spindle, the distance 62 from the lowermost end of the electrode 10 to the upper face of work 14 can be obtained thus to obtain the height of the work 14. Then the height 63 of the work 14 is added with specific height of working liquid level over the upper face of work to obtain the optimal height of working liquid level for that work resulting in prevension of fire or submergence of various units into the oil.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention Fi electric discharge machining apparatus C, in particular, has an electrode and a workpiece facing each other with an insulating machining fluid interposed therebetween, and a The present invention also relates to an electric discharge machining apparatus for machining a workpiece by generating an electric discharge within the machining gap.

[Conventional technology]

FIG. 4 is a schematic configuration diagram showing a conventional electrical discharge machining device.
In the figure, electrode 10. It faces a workpiece 14 placed in a processing tank 12 with an insulating processing fluid 16 interposed therebetween. A processing power source 18 is connected between the electrode 10 and the workpiece 14.

This machining power source 18 is composed of a DC power source 18a, a switching element 18b for controlling the machining current on and off, a current limiting resistor 18C, and a oscillator 18d for controlling the on/off of the switching element 18b. The voltage value a is intermittently supplied to the inter-electrode gap 20 where the electrode 10 and the workpiece 14 face each other, R is the resistance value of the current limiting resistor 18C, and Vg td is the inter-electrode voltage value. The interelectrode voltage value Vg is 20 to 30 V during arc discharge, and during short circuit! /i0■, becomes ViEV during no discharge, and becomes Ov when the switching element 18b is in the off state.

Therefore, if this inter-electrode voltage value Vg is detected and averaged by the smoothing circuit 22, the inter-electrode gap control can be performed using this value. That is, when the gap between the electrodes is wide, discharge is difficult to occur and the average voltage value VS is higher. When the gap between the electrodes is narrow, short circuits or discharges occur easily, resulting in a decrease in the average voltage value Vs h. Therefore, this average voltage value VB is compared with the reference voltage value vr, and this difference is amplified by the amplifier 24 to increase the hydraulic servo coil 2.
6, the hydraulic pressure generating bonder 28 and the hydraulic cylinder 3
A hydraulic servo mechanism consisting of 0 and 2
The electrode 10 can be controlled so that 0 is approximately constant.

In the electrical discharge machining equipment described above, flammable liquid is often used as the insulating machining fluid.If an arc discharge occurs near the surface of the insulating machining fluid, the sparks from the discharge will ignite the insulating machining fluid, causing a fire. This is dangerous and requires the level of the insulating machining fluid to be higher than the workpiece by a certain distance.

[Problem that the invention seeks to solve]

Conventionally, the setting of the liquid level height was determined by the operator's judgment, so if the level of the insulating machining liquid was set too high,
Precision equipment such as the device holding the electrode and the electrode angle indexing device is submerged in the liquid, and foreign matter such as processing powder and sludge mixed in the liquid enters the precision equipment and 'fI! There was a problem in that secret confusion occurred.

The present invention has been made to solve these problems, and its object is to provide an electrical discharge machining device that is pressurized to prevent the occurrence of fire and the formation of an oil film on electrode holding equipment, etc.

[Means for solving problems]

The electric discharge machining apparatus according to the present invention includes a detection means for detecting the height of a workpiece, and a height of the workpiece detected by the detection means, and a predetermined machining fluid level height. The apparatus is equipped with a machining fluid amount determining means for determining the optimum height of the machining fluid level and outputting a signal, and a control device for controlling the machining fluid amount based on the output of this determining means.

(Operation) In the present invention, when the height of the workpiece is detected by the detection means, the determination means determines the minimum necessary pre-defined machining on the upper surface of the workpiece based on the detected height of the workpiece. By adding the liquid level height, the optimum height of the machining liquid level is determined, and based on this determination signal, the control device controls the amount of the machining liquid so that the machining liquid level reaches the optimum height.

Embodiment] FIG. 1 is a block diagram showing an embodiment of the present invention, and the same parts as in FIG. 4 are given the same reference numerals.

In FIG. 1, a detection device 19 includes an electrode 10 and a workpiece 1.
4 is in contact with the DC power source 19a,
A resistor 19b for limiting the current flowing when the electrode 10 and the workpiece 14 come into contact, and a detection device 19 from the processing power source 18
and a switch 19C for disconnecting.

31V'i This is a main shaft supported by a hydraulic cylinder 30 so that it can move forward and backward, and a device 32 for holding the electrode 10 is attached to the lower end of this main shaft 31.

51 is a movement distance detector (pulse scale) of the main shaft 31
Each time the pointer 31a integrated with the main shaft passes over the scale 51a as the main shaft 31 moves, that is, the scale 51a
If it is every 1 mm, a pulse is generated from the pulse generator 50 every time the main shaft 317ji1rITrl moves, and is transmitted to the NC device 40.

The NC device 40 includes an output circuit 4-Oa that outputs a command signal for moving the main shaft to the hydraulic servo coil 26.

A device 40b that counts pulses transmitted from the pulse generator 50 (for example, pulses generated when the main shaft 31 moves forward are added and pulses generated when the main shaft 31 moves backward are subtracted).
1 A device 40C for receiving the output signal from the detection device 19 and determining whether the electrode 10 and the workpiece 14 have contacted each other.
Built-in.

In other words, the NC device 40 has the functions of a detection means for detecting the height of the workpiece 14 and a machining fluid amount determining means for determining the optimum height of the machining fluid level and outputting a signal.

60 represents the distance from the lower end of the main spindle 31 to the bottom surface of the processing tank 12 when the main spindle 31 is at the upper limit, and this distance is now designated as Hm.

This length is the sum of the length of the 61 electrodes 10 and the length of the device 32 for holding the electrodes 10, and this length is now designated as Ht.

62 is the distance from the lowest end of the electric fence 10 to the upper surface of the workpiece 14 when the main shaft 31 is at the upper limit, and this is now designated as Hd.

63Vi is the height of the workpiece 14 and 1. Now, turn this into H
Let it be w.

As mentioned above, assuming Hm, Ht, Hd, and Hw, the height Hw of the workpiece 14 can be determined by calculating Hw - Hm - Ht - Hd - (1) using the NC device 40. I can do it.

The above Hm is uniquely defined by the size of the electric discharge machining apparatus, and Ht is uniquely determined by the size of the electrode 10 and the device 32 for holding the electrode 10. Therefore, if Hd can be known, HW can be determined.

Therefore, if the switch 19e of the detection device 19 is closed at a time when no machining is being performed (point t! in Figure 2), the electrode 10
A voltage is applied between the workpiece 14 and the workpiece 14 . In this state, when a spindle movement command is issued from the NC device 40 to the hydraulic servo coil 26, the spindle 31 starts moving, a pulse P is generated from the pulse generator 50, and a device that counts the pulses in the NC device 40 The number of generated pulses is counted at 40b. When the main shaft 31 gradually moves and the electrode 10 and the workpiece 14 come into contact (point t2 in FIG. 2), the detection device 19
The output signal from is at O level.

When this change in signal level is transmitted to the NC device 40, the movement of the main shaft 31 is stopped. At this time, the pulse generator 50 simultaneously stops generating pulses.

Therefore, if we count the number of pulses generated from the start of spindle movement to the stop of spindle movement, then from K, the distance that the spindle 31 has moved until the electrode 10 comes into contact with the workpiece 14, that is, from the lowest end of the electrode 10. The distance Hd to the top surface of the workpiece 14 can be known.

By substituting the HdO value obtained in this way into the above equation (1), the height Hw of the workpiece 14 can be determined.

If we add the predetermined minimum height of the machining fluid level above the workpiece to the height Hw of the workpiece 14 obtained in this way, then It is possible to obtain the machining liquid level height.

Fig. 3 shows the configuration of a device for controlling the machining liquid level height. In Fig. 3, 64 is the minimum distance to the machining liquid level 16a above the workpiece to prevent a fire from occurring.
Now, assume that this is Hs. Then, the NC device 40 calculates Hw -)-Hs to determine the optimum machining liquid level height, and the NC device 40 gives a control command to the electromagnetic pulp 101 to maintain this machining liquid level height. . This electromagnetic pulp 101 opens and closes based on control commands given from the NC device e40, and supplies the machining fluid sucked up from the machining fluid tank 99 by the machining fluid supply port 100 to the pipe 10.
3 into the processing tank 12, and this processing tank 1
This is to always maintain the machining liquid level in No. 2 at the optimum height.

In the above embodiment, the amount of machining fluid is controlled by opening and closing the electromagnetic pulp provided in the middle of the insulating machining fluid supply pipe in response to the detection signal from the detection device 19. The same effect as in the above embodiment can be obtained even if the liquid level is controlled by changing the discharge amount when the liquid level exceeds a specified amount.

〔Effect of the invention〕

As described above, according to the present invention, the height of the workpiece is determined and the optimal height of the insulating machining liquid level is automatically set based on the determination result. This has the effect of preventing fires during automatic machining of workpieces, and preventing oil immersion in electrode holding devices, electrode angle indexing devices, etc.

[Brief explanation of drawings]

1'ffl is a diagram explaining the principle of this invention, Figure 2 is a timing chart showing the relationship between the movement of the spindle and the pulses generated by the pulse generator, and Figure 3 is a diagram of the device that controls the machining fluid level according to the discrimination signal. The schematic configuration diagram, FIG. 4, is a principle diagram showing a conventional electric discharge machining apparatus. 10 is an electrode, 14 is a workpiece, 16 is an insulating processing liquid, 4
0 detection means and judgment means (NC device), 101 control device (electromagnetic pulp). In addition, in the figures, the same reference numerals indicate the same or equivalent parts. Patent applicant: San-Ai Electric Co., Ltd. Procedural amendment (voluntary) 60.7.12 Showa Year Month Date

Claims (1)

[Claims] The electrode and the workpiece are placed facing each other with an insulating processing fluid interposed between them.
In an electric discharge machining apparatus that processes the workpiece by generating an electric discharge between the electrode and the workpiece, the height of the workpiece is detected by a detection means for detecting the height of the workpiece, and the height of the workpiece is detected by the detection means. A machining fluid volume determining means that determines the optimal height of the machining fluid level by adding a predetermined fluid level height of the insulating machining fluid to the height and outputs a signal; 1. An electric discharge machining device comprising a control device that controls the amount of machining fluid based on the amount of machining fluid.