JPS63154B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improvements in wire cut electrical discharge machining equipment.

Wire cut electrical discharge machining equipment applies
Wire electrodes running in the longitudinal direction are brought close to each other, machining fluid is injected between the wire electrodes and the workpiece, and a voltage is applied to the gap between them to cause spark discharge. Process it into the desired shape by scraping it off. The machining speed of this wire-cut electrical discharge machining device is determined by the discharge energy in the spark discharge and the repetition frequency of the discharge, but in reality it is limited by wire electrode breakage and short circuits between the wire electrode and the workpiece. .

In other words, in general, in order to increase the machining speed, use a current waveform with a large current peak value with a small pulse width, increase the discharge energy, and increase the amount of workpiece removed by one discharge. good.
This is because machining debris can be effectively removed due to the high pressure in the machining fluid generated by the large current discharge, and the electromagnetic repulsion force exerted between the wire electrode and the workpiece due to the large current discharge. increases, which excites vibrations in the wire electrode, which helps prevent short circuits.

In order to increase the discharge energy, it is possible to increase the power supply voltage, but if the voltage applied to the gap is too high, concentrated discharge will occur due to the influence of machining debris and residual ions on the wire electrode surface, which may cause the wire electrode to break. Cause. In other words, if the voltage applied to the gap is low, discharge will occur with a small gap between the wire electrode and the workpiece, so the discharges that occur one after another after the first discharge will move to multiple locations on the workpiece surface. This is because it becomes easier and therefore it becomes difficult for concentrated discharge to occur between the wire electrode and the object to be machined.

However, if the power supply voltage is reduced, it becomes difficult to reduce the pulse width and create a current waveform with a large peak value, and the gap also becomes smaller, making short circuits more likely to occur due to the influence of processing debris. Become.

Generally, in order to reduce the pulse width and create a current waveform with a large peak value, it is possible to reduce the stray inductance of the discharge circuit, but in wire-cut electrical discharge machining equipment, the table on which the workpiece is placed moves. The length of the discharge circuit has become long due to reasons such as the above, and it is not easy to reduce the inductance due to constraints on its structure.

The present invention is an attempt to solve the various contradictions mentioned above, and its purpose is to obtain a wire-cut electric discharge machining apparatus that can increase the machining speed as much as possible.

In order to achieve the above-mentioned objects of the present invention, the present invention provides a wire-cut electric discharge machining apparatus for machining a workpiece by intermittently generating spark discharge in the gap between a wire electrode and a workpiece. a first switching circuit that controls on/off the low voltage discharge power supply voltage applied to the gap; and a second voltage value higher than the first voltage value. a second switching circuit that controls on/off the high voltage discharge power supply voltage applied to the gap; a voltage detection means that detects the voltage between the gaps; a first gate circuit that turns on the first switching circuit and turns off the first switching circuit when the voltage detected by the voltage detection means falls below the first voltage;
and a second gate circuit that turns on the second switching circuit when the voltage detected by the voltage detection means is lower than the first voltage and turns off the second switching circuit when the discharge ends. The present invention provides a wire cut electric discharge machining device having the following characteristics.

An embodiment of the present invention will be described in detail using the drawings.

FIG. 1 is a circuit diagram showing an embodiment of the present invention, in which 1 is a low voltage DC power supply, 2 is a wire electrode, and 3 is a circuit diagram showing an embodiment of the present invention.
Reference numeral 4 denotes an object to be processed, and 4 is a switching transistor that controls on/off the voltage of a low-voltage DC power supply 1 applied to the gap between the wire electrode 2 and the object 3 to be processed. 5 is a current limiting resistor, 6 is a protection diode, and 7 is a switching transistor 4 on/off switch.
In the gate circuit that controls turning off, a signal generated from this is generated when a predetermined time elapses after the spark discharge generated in the gap between the wire electrode 2 and the workpiece 3 ends (for example, in FIG. 2,
t ₁ , t ₄ ), the pulse rises to turn on the switching transistor 4, and falls when a spark is generated in the gap by the low-voltage DC power supply 1 (t ₂ in FIG. 2).

8 is a high voltage DC power supply, 9 is a discharge capacitor, 1
0 is a current limiting resistor, 11 is a discharging capacitor, 9 is a switching transistor that controls the discharge of the charged charge, 12 is a gate circuit that controls the on/off of the switching transistor 11, and the signal that is generated from this. Immediately after the spark discharge based on the low-voltage DC power supply 1 starts between the wire electrode 2 and the workpiece 3 (at t ₂ in FIG. 2), the switching transistor 11 is turned on.
After a predetermined period of time (in Figure 2, at the end of discharge)
t ₃ ) and the switching transistor 11
It is a pulse that turns off the Note that 13 is a protection diode, 14 is a diode for passing a reverse discharge current, and 15 and 16 are dividing resistors for detecting the gap voltage V _G .

Next, the operation of the above embodiment will be explained.

In the process of machining the workpiece 3 by causing intermittent spark discharge between the wire electrode 2 and the workpiece 5, at time _t1 when a predetermined period of time has elapsed since the previous spark discharge ended, as shown in FIG. As shown in a,
A pulse signal is generated from the gate circuit 7 and applied to the switching transistor 4 to turn it on. When the switching transistor 4 is turned on, the voltage _E1 of the low voltage DC power supply 1 is applied to the gap, and the gap voltage _VG is as shown in Fig. 2b.
E rises to ₁ . Then, while the wire electrode 2 is running in its longitudinal direction, it grasps the tightness of the discharge, and the time t ₂
When a spark discharge occurs from the low-voltage DC power supply 1 at , the gap voltage V _G decreases from E ₁ due to the discharge.
The voltage detecting means provided in the gate circuit 7 detects this and causes the pulse to fall, turning off the switching transistor 4 and increasing the gap voltage.
The voltage detection means provided in the gate circuit 12 detects the drop in V _G , and a pulse is output from the gate circuit 12, turning on the switching transistor 11 (FIG. 2c).

When the switching transistor 11 is turned on, the electric charge stored in the discharging capacitor 9 from the high-voltage DC power supply 8 via the resistor 10 flows through the gap, and a spark discharge due to the high voltage occurs following the spark discharge due to the low voltage. As shown in FIG. 2d, a large sine-shaped discharge power source I _G flows through the gap, and a portion of the workpiece 3 where the discharge is located is scraped off by this spark discharge.

At time _t3 , when the discharge ends, the gate circuit 12
When the pulse falls, the switching transistor 11 is turned off, and one cycle of electrical discharge machining is completed.

Further, after a certain period of time has elapsed, at time _t4 when the ions in the gap have disappeared or are close to disappearing, the gate circuit 7 outputs a pulse again, and the same spark discharge cycle as described above is repeated.

Generally, in a unipolar discharge in which the gap current flows only in one direction, the number of discharge repetitions decreases, but the diode 14 allows reverse current (the part shown by the dotted line in FIG. 2 d)) and can avoid unipolar discharge.

In the above embodiment, the discharging capacitor 9 can be omitted, but by providing this capacitor, the switching transistor 11 can be closed when the discharge current becomes sufficiently small after discharging. Therefore, the load applied to the switching transistor can be reduced.

As explained in detail above, the present invention first uses a low-voltage power supply to create discharge tensions at multiple locations between the wire and the machined surface of the workpiece, so that it is difficult to repeatedly generate discharges. In this case, the discharge points can be dispersed without causing so-called concentrated discharge where the discharge points gather in one place,
Wire breakage can be reduced and processing speed can be improved.

In addition, since the process is performed using a large current pulse from a high voltage power source after creating a strong discharge using a low voltage power source, the amount that can be removed from the workpiece by spark discharge increases. , the gap becomes larger and short circuits are prevented.
Therefore, the processing speed can be improved.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, and FIGS. 2a to 2d are waveform diagrams of various parts in the embodiment. In the figure, 1 is a low-voltage DC power supply, 2 is a wire electrode, and 3
is the object to be processed, 4 and 11 are switching transistors, 5 and 10 are current limiting resistors, 6 and 13 are protection diodes, 7 and 12 are gate circuits, 8 is a high-voltage DC power supply, 9 is a discharge capacitor,
14 is a diode, and 15 and 16 are resistors.

Claims (1)

[Scope of Claims] 1. A low-voltage discharge power source having a first voltage value in a wire-cut electric discharge machining device that processes a workpiece by intermittently generating spark discharge in the gap between a wire electrode and a workpiece. a first switching circuit that controls on/off a low-voltage discharge power supply voltage applied to the gap; a high-voltage discharge power supply having a second voltage value higher than the first voltage value; a second switching circuit that controls on/off the applied high-voltage discharge power supply voltage; a voltage detection means that detects the voltage between the gaps; a first gate circuit that turns off the first switching circuit when the detection voltage of the detection means falls below a first voltage; and a first gate circuit that turns off the first switching circuit when the detection voltage of the voltage detection means falls below the first voltage. A wire-cut electrical discharge machining apparatus comprising: a second gate circuit that turns on a second switching circuit and turns off the second switching circuit when discharge ends. 2. The wire cut electric discharge machining apparatus according to claim 1, wherein the high voltage discharge power source includes a capacitor charged with electric charge through a current limiting resistor.