JPS58217231A - Electric discharge machine - Google Patents

Abstract

PURPOSE:To improve the efficiency of electric discharge work by detecting the working voltage of a plurality of electrodes and workpiece to be fed through same drive shaft then controlling the returning direction with the maximum level while the feeding direction with minimum level. CONSTITUTION:A plurality of electrodes are fed through same drive shaft while independent working power source is connected to each electrode to perform electric discharge machining. The working voltages 441-444 across each electrode and workpiece are detected to decide the maximum level 44H and minimum level 44L. When the minimum level 44L exceeds over the referential level Vo the electrode is fed toward the workpiece while when it is lower than Vo the electrode is controlled to return. The servo voltage for feed control is exchanged to be the maximum level 44H for the feeding direction while to be the minimum level 44L for the returning direction. When employing the maximum and minimum feeding speed, the machining efficiency can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electric discharge machining apparatus, in particular, to a
The present invention relates to an electric discharge machining apparatus that connects independent electric discharge machining power supplies between a plurality of electrodes that are electrically insulated from each other and the same workpiece, and performs electric discharge machining on the workpiece.

FIG. 1 shows a circuit diagram of a conventional electric discharge machining apparatus of this type. In FIG. 1, the electric discharge machining power source TO has four independent voltage sources El-. The power supply feeder 12.14.16.18 is connected to the voltage source g1. g
4 and electrodes 20, 22, 24, and 26, respectively. The earth E0 of the above four voltage sources is the power feeder 28
and is connected to the workpiece 30. Each of the above electrodes is attached to an insulating plate 32 to be electrically insulated from each other, and the insulating plate 32 is attached to a drive shaft 34a of an electrode drive device 34. This electrode drive device receives an electrode feed command voltage 36 from an electrode feed direction determination circuit to be described later, and feeds all the electrodes 20 degrees 22, 24, 26 to the workpiece 3o and returns them.

Voltage dividing circuit 38ij: Each of the above electrodes 20 to 26 and the workpiece 3
It divides the machining voltage between 0 and 0, and is composed of voltage dividing resistors 40 and 42 connected in series, and outputs the inter-electrode detection voltage 44 to the lowest voltage follower circuit 46. This lowest voltage follower circuit 46 outputs the lowest inter-electrode detection voltage 44L among the inter-electrode detection voltages 44 to the electrode feeding direction determination circuit (level shift) circuit s4, and includes a pull-up resistor 48, an operational amplifier 5o, and a diode. 52 is an ideal diode wired OR circuit. The electrode feeding direction determining circuit 54 shifts the OV level of the input minimum inter-electrode detection voltage 44L by a reference voltage vo and outputs the inter-electrode detection voltage 36.

Conventional electrical discharge machining equipment consists of the circuit configuration described above.
Below, the manner in which the electrodes 20 to 26 are driven is shown in Figures 2 and 3.
This will be explained with reference to the figures and FIG. Electrodes 20-26
The machining voltage generated between the workpiece 3o and the workpiece 3o is divided by a voltage dividing circuit 38.

FIG. 2 is a graph showing an example of the divided machining voltage, in which the horizontal axis represents time and the vertical axis represents the divided machining voltage. In FIG. 2, the detected voltage between the electrodes 20 and the workpiece 30 is expressed by a graph 4411, the electrode 22 and the workpiece 3.
A graph 442 shows the voltage detected between the electrodes at 0, a graph 443 shows the voltage detected between the electrodes 24 and the workpiece 30, and a graph 444 shows the voltage detected between the electrodes 26 and the workpiece 30. Of the four interelectrode detection voltages 441 to 444, only the lowest interelectrode detection voltage is selected by the lowest voltage follower circuit 46, and the bold line graph 44L in FIG. 2 is output.

The output of the graph 44L, which is the minimum voltage detected between the electrodes, is
The signal is input to the electrode feeding direction determination circuit 54.

In the judgment circuit 54, the input interelectrode detection minimum voltage 4
4L and reference voltage■. When the difference is positive, the sign is reversed and the electrode is fed, and an electrode feeding speed command proportional to the difference is output to the electrode driving device 34.

When the difference is negative, the sign is reversed and the electrode is returned, and an electrode return speed command proportional to the difference is output to the electrode driving device 34.

FIG. 3 is a graph showing the electrode feed command voltage 36 output from the determination circuit 54. In Fig. 3, the horizontal axis represents time and the vertical axis represents the electrode feeding speed.The electrode feeding speed at time t is proportional to the electrode feeding command voltage, and this example is plotted on the horizontal axis. This is shown in FIG. 4, which shows the feeding command voltage and the vertical axis shows the electrode feeding speed. This example shows that four electrodes are fed in at the smallest speed (v38!) among the four electrode feeding speeds. In other words, the electrode with the lowest feeding speed is servoed.

Therefore, the detection voltage between the four electrodes is all the reference voltage V
0, the electrode and workpiece are almost open, and the electrodes are fed at the same time at the lowest electrode feeding speed when the frequency of discharge is low. It takes a long time to feed the electrode until it reaches the gap between the electrode and the object. This electrode feeding time is a time that does not contribute to electrical discharge machining, and as the electrode feeding command time increases, the proportion of electrical discharge machining time in the total time decreases, increasing the electrical discharge machining speed. There are drawbacks that are an obstacle to this. Further, since the machining voltage of each electrode is different, the machining speed of each electrode is not constant, and the machining surface of the workpiece is uniform, resulting in a disadvantage.

The present invention has been made in view of the above-mentioned conventional problems, and its purpose is to feed the electrode at the maximum speed during the electrode feeding command time and at a speed suitable for the state of the electrode gap, and to quickly increase the frequency of discharge to a sufficient level. Increase the gap between the electrode and the workpiece, reduce the time required to feed the electrode, increase the proportion of the time for electrical discharge machining in the total time, increase the electrical discharge machining speed, and increase the distance between each electrode. It is an object of the present invention to provide an electric discharge machining apparatus that can reduce variations in machining voltage and make the machined surface of a workpiece uniform.

In order to achieve the above object, the present invention connects independent electric discharge machining power supplies between a plurality of electrodes fixed to the same drive shaft and electrically insulated from each other and the same workpiece,
The electrical discharge machining device for electrical discharge machining the workpiece includes a highest voltage follower circuit that outputs a voltage proportional to the highest voltage between the plurality of electrodes and the workpiece, and a minimum voltage between the plurality of power supplies and the workpiece. The lowest voltage follower circuit outputs a voltage 1" higher than the maximum voltage follower circuit, and the highest voltage detected between the electrodes input from the highest voltage follower circuit and the lowest voltage detected between the electrodes manually inputted from the lowest voltage follower circuit are set as a reference voltage. and an electrode feeding direction determination circuit that determines the electrode feeding direction by comparing the electrode feeding direction, and when the electrode feeding direction determining circuit determines feeding, all the electrodes are driven at the highest feeding speed, and the electrodes are driven at the highest feeding speed. The present invention is characterized in that, when a return determination is made from the electrode feeding direction determination circuit, all electrodes are driven at the highest return speed.

Hereinafter, preferred embodiments of the present invention will be described based on the drawings. FIG. 5 is a circuit configuration diagram showing an embodiment of the electrical discharge machining apparatus according to the present invention, in which the same parts as in FIG. 1 are given the same reference numerals. In FIG. 5, the highest voltage follower circuit 56 outputs the highest inter-electrode detection voltage among the inter-electrode detection voltages 44, and includes a pull-down resistor 58 and an operational L-amp 60.
This is an ideal diode wired OR circuit composed of a diode 62 and a diode 62. The electrode feeding direction determination circuit 64 shifts the Ov level of the output 44L from the lowest voltage follower circuit 46 by a reference voltage vo, and outputs the same to the next switch circuit 66, and an operational amplifier circuit 68, which shifts the Ov level of the output 44L from the lowest voltage follower circuit 46 and outputs the same to the next switch circuit 66, and the output from the highest voltage follower circuit 56. an operational amplifier circuit 72 that shifts the Ov level of 44H using a reference voltage vo and outputs it to the next switch circuit 70; a switch circuit 66 that is turned on when the output of the operational amplifier circuit 68 is positive; Switch circuit 7 that turns on when the output is negative
Consists of 0. Then, the switch circuit 66
Alternatively, the electrode feed command voltage 74 is output from the switch circuit 70 to the electrode drive device 34.

One embodiment of the electrical discharge machining apparatus of the present invention has the circuit configuration described above, and the manner in which the electrodes 20 to 26 are driven will be explained below with reference to FIGS. 5, 6, and 7. . The machining voltage generated between each of the electrodes 20 to 26 and the workpiece 30 is divided by a voltage dividing circuit 38.

FIG. 6 is a graph showing an example of the divided machining voltage, in which the horizontal axis represents time and the vertical axis represents the divided machining voltage. The voltage detected between the electrode 2o and the workpiece 30 is shown in a graph 4411, the voltage detected between the electrode 22 and the workpiece 30 is shown in a graph 442, the voltage detected between the electrode 24 and the workpiece 3o is shown in a graph 443, and the voltage detected between the electrodes 26 and 30 is shown in a graph 441. A graph 444 shows the voltage detected between the electrodes of the workpiece 3o.

The above-mentioned four interelectrode voltages 441 to 444 are selected by the lowest voltage follower circuit 46 and the highest voltage follower circuit 56 to select only the lowest interelectrode voltage or only the highest interelectrode voltage, respectively, as shown in the bold line graph of FIG. 44L and 44H are output.

The outputs of the graphs 44L and 44H, which are the lowest voltage detected between the electrodes and the highest voltage detected between the electrodes, are input to the electrode feeding direction determination circuit 64. In the determination circuit 64, the input interelectrode detection lowest voltage 44L is used as a reference voltage V. If the difference is negative, the sign is inverted and the switch circuit 6
6 is turned on, and an electrode return speed command proportional to the above difference is output to the electrode drive device 34 so as to return the electrode. When the above-mentioned difference is positive, the switch circuit 70 is turned ON, and the inter-electrode detection maximum voltage 44H and the reference voltage v are inputted.

The electrode driving device 3 instructs the electrode feeding speed command proportional to the above difference to feed the electrode by taking the difference between the two and reversing its sign.
Output to 4.

The graph in FIG. 7 shows the electrode feed command voltage 74 output from the determination circuit 64, and in FIG.
The feeding speed of the electrode in No. 1 is as shown in FIG. 4 above. This example shows that four electrodes are fed at the highest speed ("r43") among the four electrode feeding speeds. That is, the electrode with the highest feeding speed is servoed.

In addition, although four electrodes were described in the above embodiment, the number of electrodes may be any number. In addition, although the reference voltage v0 was used to determine the electrode feeding direction, other determination methods may be used, such as using the frequency of occurrence of the number of discharge pulses per unit time as a reference, or converting the inter-electrode voltage from voltage to frequency. The number of pulses may be input into a computer or the like, and electrode feeding may be determined based on other interelectrode parameters.

As described above, in the present invention, the interelectrode detection voltage of each electrode is all the reference voltage V. The structure is such that the electrodes are fed at the same time at a speed that corresponds to the electrode-to-electrode condition, and the discharge frequency is the highest when the gap between the electrode and the workpiece is almost open and the discharge frequency is low. It does not take time to feed the electrode until it reaches a gap between the electrode and the workpiece where there is a sufficiently large number of electrodes. That is, the proportion of time contributing to electrical discharge machining in the total time increases, and the electrical discharge machining speed becomes faster. In addition, all machining voltages are included between the highest and lowest voltages detected between each electrode, so the machining voltages of each electrode are the same, there is little variation in machining speed, and the machined surface of the workpiece is uniform. Therefore, the present invention is particularly suitable for machining with a dull electric discharge machining device having a large number of electrodes.

[Brief explanation of drawings]

Figure 1 is a circuit configuration diagram of a conventional electric discharge machining device, Figure 2 is a diagram showing the voltage detected between the electrodes in the circuit of Figure 1, Figure 3 is a diagram showing the voltage sending command voltage in the circuit of Figure 1, Figure 4 is a diagram showing the relationship between the electrode feed command voltage and the electrode feed command speed.
FIG. 5 is a circuit configuration diagram of the electric discharge machining apparatus of the present invention, FIG. 6 is a diagram showing the voltage detected between the electrodes in the circuit shown in FIG. 5, and FIG. 7 is a diagram showing the electrode feed command voltage in the circuit shown in FIG. 5. . In each figure, the same members are given the same symbols, 10 is a power source for electric discharge machining, 12.14.16.18.28 is a power feeder, 20, 22.24.26 is an electrode, 30 is a workpiece, 3
2 is an insulating plate, 34 is an electrode drive device, 36.74 is an electrode feed command voltage, 38 is a voltage dividing circuit, 40 and 42 are voltage dividing resistors, 44 is a detection voltage between electrodes, 46 is a minimum voltage follower circuit, 48 is a pro-assembly resistor, 50.60 is an operational amplifier,
52.62 is a diode, 54.64 is an electrode sending direction determination circuit (level shift circuit), 56 is a highest voltage follower circuit, 58 is a pull-down resistor, 66.70 is a switch circuit, and 68.72 is an operational amplifier circuit. Agent Patent Attorney Shin Kuzuno - (and others) Figure 1 Figure 2 Figure 3 Telephone reference 11L Figure 4 Mr. Commissioner of the Patent Office 1. Display of the case Special application No. 57 983 August 2
, Benefits of the invention, Atsushi's addition device 3, Representative Hitoshi Katayama of the person making the amendment Part 4, Agent details: 11 inventions σ red T details / 1 explanation, +su+no: IY1.1. that's all

Claims (1)

[Claims] (1) Electrical discharge in which independent electrical discharge machining power sources are connected between a plurality of electrodes fixed to the same drive shaft and electrically insulated from each other and the same workpiece, and the workpiece is electrically discharged. In the processing device, a highest voltage follower circuit outputs a voltage proportional to the highest voltage between the plurality of electrodes and the workpiece, and a lowest voltage follower circuit outputs a voltage proportional to the lowest voltage between the plurality of electrodes and the workpiece. a follower circuit, and an electrode feeding device that determines the electrode feeding direction by comparing the highest voltage detected between the electrodes input from the highest voltage follower circuit and the lowest voltage detected between the electrodes inputted from the lowest voltage follower circuit with a reference voltage. If the electrode feeding direction judgment circuit determines that the electrode feeding direction is full, all electrodes are driven at the highest feeding speed, and the electrode feeding direction judgment circuit drives the electrodes at the highest feeding speed. An electric discharge machining apparatus characterized in that, when a return is determined, all electrodes are driven at the highest return speed.