JPS6240125B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a wire cut electrical discharge machining apparatus using wire electrodes.

Since wire-cut electric discharge machining equipment uses thin wires as electrodes, accidents occur in which the wire electrodes break due to changes in machining conditions. For example, at a curved corner (corner part) of a cutting trajectory, the machining area is smaller than that at a straight part, and the discharge frequency is lower, so the average machining voltage increases rapidly. By the way, in die-sinking electric discharge machining, if the machining area is small, the electric discharge will not be sufficiently dispersed over the machining surface unless the machining power is reduced, causing arc discharge and making the machining unstable. This is the same in wire cut electrical discharge machining; in corners where the machining area is small, unless the machining power is reduced, the discharge becomes unstable and arc discharge (discharge that does not contribute to machining) occurs. , the wire electrode is likely to break. Furthermore, it is empirically known that even after the wire electrode passes through a corner portion, the wire electrode tends to break until it moves a certain distance (approximately 0 to 3 mm).

The purpose of the present invention is to avoid breakage of the wire electrode due to machining at corners where the condition between the machining areas becomes unstable. The bending angle is detected when it has risen above a predetermined level, and the pause time of the pulse voltage applied to the machining gap is increased to reduce the machining power of the machining gap, and the period of the pulse applied to the electrode drive motor is increased. This is achieved by changing the processing speed to lower the machining feed rate and returning to the initial state by counting a predetermined number of drive pulses. Examples will be described in detail below.

FIG. 1 is a block diagram of a wire cut electrical discharge machining apparatus according to an embodiment of the present invention, and FIG. 2 shows its operating waveforms.

In Figure 1, P is the wire electrode, W is the workpiece, Vs is the DC high voltage power supply that outputs the machining voltage, TR
are switching elements such as switching transistors, OS1 and OS2 are pulse oscillators, C1 and C
2 is a capacitor, R1 to R4 are resistors, RV1 is an adjustment resistor, Q1 is a comparator, M is a motor, SA
is a servo amplifier, FF is a flip-flop, G1
is a gate and CU is a counter.

The transistor TR is repeatedly turned on and off by the output pulse D of the pulse oscillator OS1, and the capacitor C1 is charged from the DC high voltage power supply Vs via the resistor R1. This charging voltage is applied between the wire electrode P and the workpiece W, and under normal conditions, the discharge current of the capacitor C1 flows into the opposing gap between them as a discharge, and electrical discharge machining is performed. The wire electrode P is controlled to be fed relative to the workpiece W by a motor M driven by amplifying the output pulse C of a pulse oscillator OS2 by a servo amplifier SA.

Also, there is a resistance R between the wire electrode P and the workpiece W.
2, R3 is connected to divide the machining voltage, and the average machining voltage V ₁ is created by resistor R4 and capacitor C2.
is obtained. This average processing voltage V ₁ is the adjustment resistance RV
When the average machining voltage _V1 increases, the flip-flop FF is set by the output of the comparator Q1. This set output A is applied to pulse oscillators OS1, OS2 and gate G1.

The pulse oscillator OS1 changes the pulse period so that the off time of the transistor TR is increased by the set output A of the flip-flop FF, and the pulse oscillator OS2 also changes the period of the output pulse C so that the speed of the motor M is decreased. do. Then, the counter CU counts the output pulses C of the pulse oscillator OS2 while the flip-flop FF is in the set state, and when the count reaches a predetermined value,
Add output pulse B as a reset pulse to flip-flop FF. This flip-flop FF
The reset causes the pulse oscillators OS1 and OS2 to return to their initial states.

Waveforms PV ₁ and PA to PD in Figure 2 are the average processing voltage V ₁ in Figure 1, set output A of flip-flop FF, output pulse B of counter CU, and pulse oscillator.
This shows the output pulse C of OS2 and the output pulse D of pulse oscillator OS1. When the average machining voltage V ₁ becomes negative in the machining state of a curved corner than the voltage during straight machining, the flip-flop FF is set; Therefore, the period of the output pulses C and D becomes slower, so the transistor TR
The machining power supplied through the wire electrode P decreases, and the feeding speed of the wire electrode P decreases.

In addition, the above-mentioned state is maintained until the count contents of the counter CU are predetermined and the flip-flop FF is reset, that is, until the feed distance after reducing the machining power and feed speed reaches a predetermined value. . Therefore, it is possible to reliably prevent the wire electrode from breaking at the bend and in a section at a predetermined distance from the bend.

As explained above, the present invention provides a detection means for detecting a location where the state between the poles of a bending angle becomes unstable by detecting that the average machining voltage of the machining gap has increased more than the reference voltage, and When the location is detected, the pulse oscillators OS1 and OS2 are controlled and the OS
A control means for reducing the machining power and relative feed speed by switching the pause time of the pulse of 1 and the pulse period of the OS 2, and controlling this control means by detecting the bending angle, and then counting the predetermined number of pulses. When he learned that he had been sent a certain distance,
It is equipped with a means for restoring the machining power and relative feed speed to their original values, and when the wire electrode is located at a bend, and when the wire electrode passes through a bend until it has moved a predetermined distance. while,
Since the machining power is lowered by extending the pause time of the pulse voltage and the relative feed speed is lowered by extending the feed pulse period, excessive machining power is not applied to the machining gap. Therefore, when the wire electrode is located at a bend in the processing path, it is possible to reliably prevent the wire electrode from breaking even after the wire electrode passes through the bend until it moves a predetermined distance. This has the advantage that wire cut electrical discharge machining can be performed smoothly.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of the present invention, and FIG.
The figure is a waveform diagram explaining the operation. P...Wire electrode, W...Work material, Vs...
DC high voltage power supply, OS1, OS2...pulse oscillator,
M...Motor, Q1...Comparator, FF...
Flip-flop, CU...Counter, TR...Switching transistor, C1, C2...Capacitor, R1-R4...Resistor.

Claims (1)

[Claims] 1. Detection for detecting the bending angle of a machining path in a wire-cut electrical discharge machining device that inserts a power supply and a switching element in series between a wire electrode and a workpiece, and applies a pulse voltage with a predetermined pause time to the machining gap to perform machining. and driving a motor for increasing the pause time of the pulse voltage applied to the machining gap when the detection output of the detection means is generated, thereby reducing the machining power, and controlling the relative feed between the wire electrode and the workpiece. a control means for reducing the relative feed speed by changing the pulse period; and after counting a predetermined number of pulses of the drive pulses from the generation of the output of the detection means, the machining power and relative feed speed reduced by the control means are returned to their original values. A wire cut electrical discharge machining device characterized by comprising means for returning the wire cut to the original state.