JPH03208520A - Machining pulse control method and device for electric discharge machine - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention applies a bipolar machining pulse to an electrode and a workpiece in a wire electrical discharge machine or a die-sinking electrical discharge machine. The present invention relates to a machining pulse control method and apparatus for an electrical discharge machine that performs machining by electrical discharge.

[Conventional technology]

Normally, a wire electric discharge machine increases the pulse current and lengthens the application time (on time) during the rough machining process to increase the discharge energy and increase the machining speed.

In the rough machining process, in order to increase the machining speed, the wire electrode side is biased to the negative side and the workpiece side is biased to the positive side. This is because damage to the wire electrode during discharge is small, damage to the machined surface of the workpiece is large, and this polarity is also appropriate for rough machining that does not require surface roughness. However, if unipolar pulses are continuously applied between the wire electrode and the workpiece, the following problems occur.

That is, when water is used as a machining fluid, an electric current flows through the water, which causes an electrolytic phenomenon, and this electrolytic phenomenon causes deterioration of the surface roughness.

In order to solve this problem, a bipolar force pulse is applied between the wire electrode and the workpiece to prevent electrolytic phenomena caused by the machining fluid from occurring. This prevents the surface roughness from deteriorating due to electrolytic phenomena, and causes the surface roughness to depend only on the applied voltage, the magnitude of the current, and the time. FIG. 4 shows the voltage waveform on the wire electrode side in this conventional gap. When the wire electrode is biased to the negative side, it is referred to as positive polarity, and when it is biased to the positive side, it is referred to as reverse polarity. As shown in the figure, in the conventional bipolar pulse application method, discharge occurs on both the positive polarity side and the negative polarity side.

[Problem to be solved by the invention]

In the conventional voltage waveform between electrodes due to bipolar pulses, discharge occurs on the positive and negative sides, and when electrical discharge machining is performed with such a waveform, no electrolytic phenomenon occurs because it is bipolar, so electrolysis occurs. Although the deterioration of surface roughness caused by this phenomenon is resolved, the surface roughness of the machined surface becomes 1.5 to 2 times rougher when the wire electrode is energized with positive polarity than when it is energized with reverse polarity. This phenomenon occurs, and there is a problem in that the overall surface roughness becomes the coarser surface roughness on the positive polarity side.

Therefore, although this is not a problem in the rough machining process, in the finishing process, if the voltage when the wire electrode is energized to the positive polarity is as high as that of the opposite polarity, it will be difficult to improve the surface roughness.

On the other hand, it is conceivable to simply bias the wire electrode side to the opposite polarity during the finishing process, but this can improve the surface roughness, but as mentioned above, the brass of the wire electrode melts due to the electrolytic phenomenon and the machined surface This causes problems such as adhesion to the surface and deterioration of the appearance of the machined surface. Similar problems occur in die-sinking electric discharge machines.

An object of the present invention is to improve the surface roughness in the finishing process of electric discharge machining, in which a bipolar voltage is applied between an electrode and a workpiece to perform electric discharge machining on the workpiece.

[Means to solve the problem]

The present invention is characterized in that bipolar machining pulses are used, and the voltage of one polarity of the voltage between the electrodes is set to a level that causes discharge, and the voltage of the other polarity is set to a level that does not cause discharge. That is. That is, in a machining pulse control method for an electrical discharge machine, in which a bipolar machining pulse is applied to an electrode and a workpiece, and the workpiece is machined by electric discharge, the voltage between the electrodes and the workpiece is The voltage of one polarity is set to a magnitude that causes discharge, the voltage of the other polarity is set to a magnitude that does not cause discharge, and the integral value of the voltage of one polarity and the voltage of the other polarity are set. There is provided a machining pulse control method for an electric discharge machine, characterized in that the application time of the voltage of one polarity and the voltage of the other electrode are set so that the integral value of In a machining pulse control device for an electric discharge machine, which generates bipolar machining pulses by turning on and off a current from a power source using a switching means, and applies the pulses to an electrode and a workpiece to machine the workpiece by electrical discharge. , an inter-electrode voltage detecting means for detecting an inter-electrode voltage between the electrode and the workpiece, and a voltage of one polarity of the inter-electrode voltage detected by the inter-electrode voltage detecting means has a magnitude at which electric discharge occurs. , a voltage control means for controlling the voltage of the machining power supply so that the voltage of the other polarity is at a level that does not cause discharge; and an integral of the voltage of one polarity of the voltage between the machining electrodes detected by the voltage detection means between the machining electrodes. and an on/off time control means for controlling the on/off time of the switching means so that the integrated value of the voltage of the other polarity becomes equal to the integrated value of the voltage of the other polarity. is provided.

[For production]

In the present invention, when electrical discharge machining is performed by applying bipolar voltages between the electrode and the workpiece, the voltage of one polarity on the wire side is set in a range that discharges, and the voltage of the other polarity is set in a range that does not discharge. This is designed to prevent surface roughness from deteriorating due to electrolytic phenomena and to improve surface roughness in the finishing process.

〔Example〕

FIG. 3 is a diagram showing the main part structure of the wire electric discharge machine of the present invention.

A wire electrical discharge machine has four basic structural elements: ■ The main body of the processing machine, which includes a wire electrode traveling mechanism and an XY table, ■ A numerical control device that controls the movement of the XY table, ■
It consists of a machining power source that generates an applied voltage, and ■ machining fluid.

The wire electrode 1 is made of first class brass (with a diameter of 0.2 to 0.3 mm).
BS) line is most often used. This is because it has good electrical conductivity, is easy to process, and is cheap.

The wire electrode 1 is connected to the upper and lower wire guides G1 that sandwich the workpiece 2.
．． It is important that the wire is always stretched straight with G2 as the fulcrum, so that appropriate tension is applied to the wire electrode.

The machining power source E is a power source for generating a discharge voltage to be applied between the wire electrode 1 serving as an electrode and the workpiece 2. The applied voltage has a pulse waveform that is interrupted by a switching means as described later.

FIG. 1 shows the voltage waveform of the wire electrode between the wire electrodes when the bipolar pulse of the present invention is applied between the wire electrodes and the workpiece and discharge is started.

As shown in the figure, the wire electrode is set to the positive side, that is, the voltage v1 that can sufficiently discharge the reverse polarity voltage, and the wire electrode is set to the negative side, that is, the limit range in which the positive polarity voltage is not discharged. Set with . In this case, voltage V2 is experimentally about 30% of voltage V1. Further, the relationship between waveforms A and B is that the integral value of waveform A (shaded area) is the integral value of waveform B (
The application time T of waveform B is set so that it is equal to the shaded area). Also, integration is not performed on each waveform one by one, but is performed on several waveforms at once by setting a sampling time to obtain the average voltage, and then perform integration so that the positive and negative values of the average voltage are equal. The application time T may be set to .

FIG. 2 is a circuit diagram of an embodiment for generating the bipolar voltage waveform of FIG. 1. As shown in the figure, a variable power source E1 is provided to generate voltage v1, and a variable power source E2 is separately provided to generate voltage V2. These two power sources are connected as shown in the figure, and switching elements SWI and SW2 are alternately connected. By switching to , the waveform shown in FIG. 1 is obtained. For example, if the switching element SWI is turned on, the voltage v on the positive side, that is, the opposite polarity
1 is applied to the wire electrode 1, and when it switches and turns on the switching element SW2, the negative side, that is, the positive polarity voltage V
2 is applied to the wire electrode 1. Note that since the workpiece 2 is connected from the position shown in the figure, the potential is 0.

Furthermore, the control circuit 3 includes a switching element SWI. The detection circuit 4 is a circuit for controlling on/off of SW2, the detection circuit 4 is a circuit for detecting the average voltage between poles, and the voltage control circuit 5 is a circuit for controlling the magnitude of voltages v1 and V2. Machining conditions are input to the control circuit 3, and furthermore, a voltage between machining electrodes is input. Based on these signals, switching elements SWI,S
The on/off time of W2 is controlled so that the integral value of the positive side voltage and the integral value of the negative side voltage of the interelectrode voltage are equal. Further, the voltage control circuit 5 controls the voltages Vl and V of the machining power sources El and E2 so that the positive side voltage of the inter-electrode voltage detected by the detection circuit 4 is in a discharge range, and the negative side voltage is a value in a non-discharge range.
2 respectively.

In this way, even if water is used as a machining fluid, electrolytic phenomena such as the wire electrode melting and adhering to the workpiece will not occur, and the electrical discharge machining will progress only when the opposite polarity has a good surface roughness. Processing can be done neatly.

It should be noted that a die-sinking electric discharge machine using a water-soluble machining fluid will also be effective if it has a similar structure.

〔Effect of the invention〕

As explained above, according to the present invention, in an electrical discharge machine that performs workpiece C electrical discharge machining by applying a bipolar pulse between an electrode and a workpiece, a voltage of one polarity of the intermachining voltage in the finishing process is used. Since the voltage is set within a range that does not cause discharge, it is possible to avoid electrolytic phenomena due to bipolar voltage, and it is also possible to significantly improve surface roughness in the finishing process.

[Brief explanation of drawings]

Fig. 1 is a diagram of the voltage waveform on the wire electrode side between the electrodes of the present invention, Fig. 2 is a schematic diagram of an embodiment of the present invention, and Fig. 3 is a diagram of the main part configuration of the wire electric discharge machine of the present invention. FIG. 4 is a voltage waveform diagram on the wire electrode side between the conventional electrodes. (Explanation of symbols) 1...Wire electrode, 2...Workpiece, 3...
- On/off control circuit, 4... Gap voltage detection circuit, 5... Voltage control circuit, E, El, E2... Processing power supply, Sll 1, SW 2... Switching element.

Claims (1)

[Claims] 1. Applying bipolar machining pulses to the electrode and the workpiece,
In the machining pulse control method for an electrical discharge machine that processes the workpiece by electrical discharge, one polarity of the voltage between the electrode and the workpiece is set to a magnitude at which electrical discharge occurs, and the other polarity is set to a magnitude that generates electrical discharge. The voltage of the one polarity and the voltage of the other polarity are set to a level that does not cause discharge, and the voltage of the one polarity and the voltage of the other polarity are set so that the integral value of the voltage of the one polarity and the integral value of the voltage of the other polarity are equal. A machining pulse control method for an electric discharge machine, characterized in that a time for applying voltage to an electrode is set. 2. A machining pulse of an electric discharge machine that turns on and off a current from a machining power supply using a switching means to generate a bipolar machining pulse, which is applied to an electrode and a workpiece to machine the workpiece by electric discharge. In the control device, an inter-electrode voltage detection means detects an inter-electrode voltage between the electrode and the workpiece, and a voltage of one polarity of the inter-electrode voltage detected by the inter-electrode voltage detection means causes discharge to occur. voltage control means for controlling the voltage of the machining power source so that the voltage of the other polarity is at a level that does not cause discharge; Machining using an electrical discharge machine, characterized in that it is equipped with on/off time control means for controlling the on/off time of the switching means so that the integral value of the voltage is equal to the integral value of the voltage of the other polarity. Pulse control device.