JPS5976724A - Wire cut electric discharge machining system - Google Patents

Abstract

PURPOSE:To prevent a wire electrode from disconnecting, by a method wherein energy of electrical discharge machining is reduced and is restored to that of a normal state gradually when instruction information for electrical discharge machining is that for a turning point. CONSTITUTION:Predetermined wire cut electric discharge machining is performed by the titled system by feeding the wire electrode P and a work W relatively by controlling action of each of motors 6X, 6Y of X and Y axes by a computation controller 4 according to a command read from a paper tape 7 through a reader 8. In this instance, command to reduce energy of electric discharge machining is given to the computation controller 4 when the wire electrode P comes to a completion point a1 of a first block and ON-OFF time of a pulse oscillator OS is made to change. A pulse whose OFF time is longer than usual is made to put out and the energy of the electric discharge machining is reduced, that is. The energy is restored every time when the wire electrode P passes through points a2, a3 and the electric discharge machining is made to perform conventionally in a fourth block.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a wire-cut electric discharge machining method using a wire electrode.

In the wire-cut electric discharge machining method, since a thin wire is used as an electrode, accidents occur in which the wire electrode breaks due to changes in machining conditions.

Particularly, the wire electrode was often broken at the bending angle of the cutting trajectory. One possible reason for this is that, for example, machining waste that remains after cutting is normally removed by the machining fluid, but at curved corners (parts of corners) of the cutting path, machining waste is not removed properly. It is being

Therefore, an object of the present invention is to prevent wire electrodes from breaking at curved corners, by reducing machining energy at curved corners, gradually returning to normal energy, and reducing wire electrode feeding speed at curved corners. An object of the present invention is to provide a wire-cut electrical discharge machining method that prevents the wire electrode from being cut by gradually returning to normal speed.

Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of the wire cut electric discharge machining method of the present invention. P is a wire electrode, W is a workpiece, El is a DC high-voltage power supply that outputs a machining voltage, and TR is a switching element, such as switching!・Langister,
O8 is a pulse oscillator, C is a capacitor, R1-R3 are resistors, 1 is an integrator, 2 is a differential amplifier that amplifies the difference between the reference voltage E2 and the output of the integrator 1, 3 is a voltage frequency converter, 4
5X and 5Y are X and Y axis control units 1 to . , respectively. 6X, 6Y are the wire electrode P and liquid addition 1. 7 is a paper tape, 8 is a tape reader, and 9 is an operation panel. Normally, the output pulse of the pulse oscillator O8 causes the transistors i to TR to turn on and off repeatedly, and the DC high-voltage power supply E
1, the capacitor C is charged via the resistor R1. This charging voltage is applied between the wire electrode P and the workpiece UW, and under normal conditions, the discharge current of the capacitor C flows into the opposing gap between them as a discharge, and electrical discharge machining is performed.

Then, the integrator 1 smoothes the voltage between the wire electrode P and the workpiece W divided by the resistors R2 and R3, and its output corresponds to the average machining voltage. The differential amplifier 2 amplifies the difference between the output of the integrator 1 and the reference voltage V and applies it to the voltage frequency converter 3, and the arithmetic control unit 4 distributes the pulse signal from the voltage frequency converter 3 to the motor 6X, 6Y
Create a signal to control the operation of the servo unit 5X.

Add to 5Y. As a result, the wire electrode 1 and the workpiece 2 are fed relative to each other at a speed such that the average machining voltage is constant. Incidentally, since the above-mentioned operation is well known, detailed explanation will be omitted.

Next, an explanation will be given of the operation at a part of the corner, which is a feature of the present invention.

FIGS. 2(A) and 2(B) are explanatory views of the machining process at a part of the corner. In FIGS. 2(A) and 2(B), the first block [1 The wire electrode P is fed at the normal feeding speed Vo, and the wire electrode P is fed from the point a1 to 82
During the second block up to 83, the wire electrode is fed at a speed V1 which is lower than the normal speed, reducing the energy and the third block from point a2 to 83 is at the normal speed V.
It is sent at a speed v2, which is slightly closer than o, and from the 410th pass from point a3, which has passed a part of the corner, it is sent at a normal speed Vo. That is, the relationship between the feeding speeds of the wire electrodes of the first to fourth blocks is as follows.

Vo>v2>V+-"." (1) Next, the above-mentioned processing steps will be explained with reference to FIGS. 1 to 3.

The end point of the first block, that is, the wire electrode is at point a
1, the arithmetic and control unit 4 executes the next instruction read from the tape 7 through the tape reader 8. That is, the instructions from tape 7 are executed for a certain period (second block period).
, is a command to reduce machining energy, and in response to this, the arithmetic and control unit 4 resets and starts the counter, counts the sending pulses from the voltage frequency converter 3, and sends a signal to the pulse oscillator O8. , the on/off time of the pulse oscillator O8 is changed to output a pulse f2 shown in FIG. 3, which has a longer off time than usual, to reduce the energy. As a result, the relative speed between the wire electrode P and the workpiece W is reduced to Vl. Next, the count value of the counter set by the command from tape 7 is the first set value (end point of the second block).
Then, the arithmetic and control unit @4 outputs a signal to the pulse oscillator O8 to change the on/off time. A pulse signal shorter than the off time of frequency 12 is sent out.

As a result, the electric discharge machining energy is decreased compared to the first block and increased compared to the second block, and as a result, the relative speed V2 between the wire electrode P and the workpiece W in the third block is the same as that shown earlier. It becomes as shown in equation (1). Furthermore, the counter is set to the second set value (end point of the third block)
When this happens, the arithmetic and control device 4 again outputs a signal, changes the oscillation of the pulse oscillator O8 to the normal oscillation pulse f1, and returns to the normal feed speed Vo.

In the above embodiment, the tape 7 was used to instruct the second block and the third block, but it is also possible to perform all these instructions by the arithmetic control device 4. That is, when the machining direction changes perpendicularly to the sea urchin in FIG. , during the 3rd block period, it is sufficient to send a signal V so that the feed speed is equal to V2t, and the settings between the 2nd and 3rd blocks $111 (settings to the JJ counter) can be set and changed from the operation panel 9. 0゜Also, if you want to take an arc trajectory for a certain period of time as shown in Figure 2 ([]), when you receive an arc trajectory command, the arc trajectory period (second block brightness) 3) Send out a pulse signal shown at t2 in FIG. 3 from the pulse oscillator O8,
Decrease the speed to ■1, start the counter at the end of the circular trajectory, and send a signal to the pulse oscillator O8 to generate the pulse signal of f3. When the counter reaches the set value, the pulse oscillator O8 will switch off to normal feed. The oscillation of 11
You can change it to

Further, in the above embodiment, the machining energy was changed by changing the on/off time of the oscillation pulse of the pulse oscillator O8, as shown in FIG. J Niuni current value (Io ~ 12
) may be used to change the electrical discharge machining energy.

In FIG. 4, some common parts with FIG. 1 are omitted. A transistor T
R-T R'' is connected, and this transistor T
R~T R'' is connected to a pulse oscillator OS through G1~0~G'' which is selectively opened by a signal from the arithmetic and control unit 4.
It receives the pulse signal from h days and turns it on and off.

The resistance values of the above-mentioned resistors R1 to R1'' are in the relationship R1',>R+''>R1, and as a result, the flowing current 1. For M and I'', 1>1''>I'.

Therefore, during the first block period and the 410th block period shown in FIG. Flow I. Furthermore, during the second block period, the arithmetic and control device 4 selects the gate G' and inputs the smallest current value 1' to the condenser C. Furthermore, in the 31st [1 block], G1-G'' is selected and the current In flows.As a result, in the 1st and 4th blocks, the maximum current value I flows, and the feed speed becomes Vo.

Next, in the second block, the electric discharge machining energy is the minimum because the current value r' is the minimum, and the feed rate is vl
becomes. Further, since the third block has an intermediate current value In, the feed rate is V2, and the relationship shown by the first equation is established.

In the above embodiment, the relative velocity of the electrode and the workpiece is divided into two stages at the curved corner, and the deceleration is divided into n stages as necessary. It may be processed. Furthermore, in the above embodiment, the current value or the on/off time of the pulse was changed to change the machining energy. good.

As described above, the present invention has a curved inner circle (a3),
Since the electric discharge machining energy and the wire electrode feeding speed are decreased and then gradually increased, breakage of the wire electrode can be prevented and wire cut electric discharge machining can be performed smoothly.

[Brief explanation of drawings]

Fig. 1 is a block diagram of an embodiment of the wire-cut electric discharge machining method of the present invention, Fig. 2 (a) and (b) are diagrams explaining the machining process at a part of the corner, and Fig. 3 is an explanation of the pulse signal. 4 are partially omitted block diagrams of other embodiments. P...Wire electrode, W...Work material, R1~R1''
...Resistor, T R-TR''...Switching element, O8...Pulse oscillator, C...Capacitor, 4.
... Arithmetic control unit, 5X, 5Y... Serboni 1 Nitsu 1
~． 6X, 6Y...Motor.

Claims (1)

[Claims] <1) In a wire cut electrical discharge machining method in which a wire electrode and a workpiece are moved relatively based on command information and the workpiece is machined into a desired shape by electric discharge, the command information is In the case of a bending angle command, the wire cut M electric machining method is characterized in that the electric discharge machining energy is reduced and then returned to the normal electric discharge machining energy in stages. (2) The wire-cut electric discharge machining method according to claim 1, wherein the electric discharge machining energy is changed by changing the on/off time of the pulse current; (3) the electric discharge machining method according to claim 1; 2. The wire-cut electric discharge machining method according to claim 1, wherein the energy is changed by changing the current value of the pulse current.