JPH06283B2 - Wire EDM power supply - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wire electric discharge machine power supply for a wire electric discharge machine, and more particularly to an electric discharge machine power supply that prevents an average machining voltage between an electrode and a workpiece from increasing.

In the prior art wire electric discharge machine, the average machining voltage between the wire electrode and the work is detected, compared with the servo voltage, and the voltage proportional to this difference voltage is pulsed by the V / F converter and sent to the numerical controller. The numerical control device controls the movement of the table in proportion to this pulse.

When such a control method is used, in the finishing process called the second cut, the average machining voltage increases and the table feed speed increases in the part where the wire and the work are distant from each other, so the machining amount decreases, and conversely. In the portion where the wire and the workpiece are close to each other, the number of discharge repetitions increases, the average machining voltage decreases, the table feed speed decreases, and the machining amount increases, which is convenient for performing highly accurate machining.

However, even if this control method is used, if the response of the table feed control is insufficient, it may cause hunting, and especially at the convex corner, the machining amount decreases sufficiently even if the electric discharge machining voltage increases. It had a drawback that it could not be cut and an accurate processed shape could not be obtained.

In order to avoid this, it is effective to increase the off-time to reduce the number of discharge repetitions at the place where the machining amount should be reduced, and to reduce the off-time at the place to increase the machining amount. The same effect can be expected if the voltage is controlled to be constant during processing. However, in such a method, the off-time may be very short in the processing that bites into the wire and the work, and if the off-time is too short, the discharge itself is not stable and the processing accuracy deteriorates rather. It had the drawback of

It is necessary to manually change the work material, plate thickness, and off-time to determine the minimum off-time for stable machining.

It is an object of the present invention to provide a switching element for turning on / off the switching element and applying a voltage from a DC power supply between a wire electrode and a work, or a charging voltage of a capacitor for electric discharge machining. The minimum off-time can be set manually in the electric-discharge machining power supply that controls the electric discharge, and the average machining voltage can be lowered by increasing the off-time when the wire electrode and the workpiece are separated, improving the finishing machining accuracy. It is intended to provide a wire electric discharge machining power supply.

The present invention relates to a wire electric discharge machining power source for controlling electric discharge by turning on / off a switching element, and a machining voltage detecting means for detecting and smoothing a difference between a voltage between a wire electrode and a work and a reference voltage, A wire electric discharge machining power supply having off-time generating means for extending a preset set off-time of the switching element according to a detection output voltage level of the machining voltage detecting means and varying the off-time.

Embodiment FIG. 1 shows an embodiment of a circuit for controlling the on-time and off-time of a switching element in a wire electric discharge machining power supply according to the present invention, where P is an electrode, W is a work and 1 is a machining voltage detecting means. Is a smoothing differential amplifier circuit, 2 is an inverting circuit, 3 is a comparator, 4 is a one-shot multivibrator for setting the on-time of the switching element, and the on-time can be set from the outside as in the past. There is. Reference numeral 5 is also a one-shot multivibrator for setting the off-time similar to the conventional one, which can also be set from the outside. In addition, T
Is a transistor, C is a capacitor, and R1 to R13 are resistors.

The voltage between the electrode P and the work W is divided by the resistors R1 and R2, and the difference between this divided voltage and the reference voltage obtained by adding a slight set voltage Vδ to the servo voltage VS is detected by the smoothing differential amplifier circuit 1. The polarity is inverted by the inversion circuit 2, and this output VL (hereinafter, this output VL is referred to as a processing level voltage) is input to the comparator 3. On the other hand, the other terminal of the comparator 3 is connected to one terminal in which the transistor T and the capacitor C are connected in parallel. The base of the transistor T is connected to a one-shot multivibrator 5 for setting the off time of the switching element of the electric discharge machining power source controlled by the switching element, and these comparator 3, transistor T, capacitor C,
The one-shot multivibrator 5 constitutes an off-time generating means. Further, the one-shot multivibrator 5 is connected to the one-shot multivibrator 4 for setting the on-time, and the trailing edge of the one-shot multivibrator 4 triggers the one-shot multivibrator 5 to generate a pulse corresponding to the set off-time. Is to occur. Therefore, the on-time and off-time control operation of the switching element of the wire electric discharge machining power supply of the present invention will be described with reference to the timing chart of FIG. 2 (a) shows the output pulse of the one-shot multivibrator 4 which outputs the on-time time set from the outside, and (b) shows the one-shot multi-vibrator 5 which outputs the off-time time set externally. The output pulse, (c) shows the waveform of the voltage VC input to the comparator 3, and (d) shows the output pulse output from the comparator 3.

Now, assume that an output pulse is output from the one-shot multivibrator 4 that outputs the set on-time, as shown in FIG. As a result, the switching element of the electric discharge machining power supply is turned on, and when electric discharge machining is performed by applying a voltage to the electrode and the work or by capacitor discharge, the capacitor is charged and electric discharge machining is performed. Then, when this output pulse disappears, as shown in Fig. 2 (b) at this falling edge,
The output of the set off time is output from the one-shot multivibrator 5. As a result, the transistor T is turned on, and the voltage VC input to the converter 3 is
Is a value close to 0V. As a result, the voltage VC becomes lower than the machining level voltage VL generated by the voltage between the work W and the electrode P, so that the output of H level is output from the comparator 3 as shown in FIG. To be done. When the set off time expires and the output of the one-shot multivibrator 5 disappears, the transistor T turns off and the bias voltage is applied to the capacitor C via the resistor R12, so that the charging voltage of the capacitor C rises. However, since the charging voltage VC of this capacitor C is input to one terminal of the comparator 3, when the input voltage VC due to this charging voltage becomes higher than the processing level voltage VL input to the other terminal of the comparator 3, As shown in FIG. 2D, L level output is obtained. The fall of the output of the comparator 3 triggers the one-shot multivibrator 4 again to turn on the switching element and repeat the above-described operation.

The above is the operation of the on-time and off-time control circuit of the wire electric discharge machining power supply according to the present invention. As described above, the machining level voltage VL is as long as the voltage between the workpiece W and the electrode P is close to the servo voltage VS. The value becomes close to 0V, and the work W and the electrode P are separated from each other due to the processing of the convex portion and the voltage between them increases, and the processing level voltage VL also increases.

As described above, the processing level voltage VL moves up and down in accordance with the voltage between the work W and the electrode P in FIG. As a result, the off-time time output from the comparator 3 increases or decreases. That is, when the processing level voltage VL moves up and down, the time width indicated by t in FIG. 2 increases or decreases, and the set output of the one-shot multivibrator 5 (FIG. 2 (b)).
Second off time extended by a time width of t
As shown in FIG. 4D, the comparator 3 outputs the data. Therefore, when the electrode P and the work W are separated from each other and the voltage between them is increased, the off-time is increased and the average machining voltage is decreased, so that stable machining can be obtained and the machining accuracy in finishing can be improved.

Although the smoothing differential amplifier circuit 1 is used in the above embodiment, the voltage between the electrode P and the work W may be smoothed, and the difference between the smoothed voltage and the reference voltage may be detected and amplified by the differential amplifier. .

EFFECTS OF THE INVENTION The present invention relates to an electric discharge machining power source for controlling electric discharge by turning on / off a switching element, when a work and an electrode are separated from each other and a voltage between them is increased. , Since the off time of the above switching element is automatically extended beyond the set off time,
The average machining voltage is reduced, machining at the corners of the convex portion during finishing machining is performed accurately, and the off-time does not become too short at the concave portion, so a stable machining state and excellent machining shape Can be obtained.

[Brief description of drawings]

FIG. 1 is a circuit diagram for controlling on-time and off-time of a switching element of a wire electric discharge machining power source according to an embodiment of the present invention, and FIG. 2 is a timing chart of the same embodiment. 1 ... Smoothing differential amplifier circuit, 2 ... Inversion circuit, 3 ... Comparator, 4, 5 ... One-shot multivibrator, P ... Electrode, W ... Work.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masafumi Tonomura 3-5-5 Asahigaoka, Hino-shi, Tokyo Fanatsuku Co., Ltd. (56) References JP-A-54-156296 (JP, A)

Claims (4)

[Claims] 1. In a wire electric discharge machining power source for controlling electric discharge by turning on / off a switching element, machining voltage detecting means for detecting and smoothing a difference between a voltage between a wire electrode and a work and a reference voltage, and preset. A wire electric discharge machining power supply having off-time generation means for adding a time substantially proportional to the magnitude of the detected output voltage level of the machining voltage detection means to the off-time of the switching element to make the off-time. 2. The wire electric discharge machining power source according to claim 1, wherein the machining voltage detecting means is a smoothing differential amplifier circuit. 3. The wire electric discharge power source according to claim 1, wherein the reference voltage is a voltage obtained by adding a slight voltage to a servo voltage. 4. The off-time generating means is discharged by a set off-time output pulse, and is output until the charging voltage of a capacitor charged when the output pulse disappears reaches a detection output voltage level of the machining voltage detecting means. The wire electric discharge power source according to claim 1, 2 or 3, wherein the output of the comparator is an off time.