JPS60207720A - Electrical discharge machining device - Google Patents

Abstract

PURPOSE:To improve the degree of surface roughness by combining a switching element and a current limiter with a DC power source and an electrode to form an electrical discharge circuit and thereby forming a discharge current waveform having a reduced pulse width and a higher peak valve. CONSTITUTION:Switching off both switching elements FETs 16a, 16b from a state thereof wherein the FETs 16a, 16b have been switched on and thereby a discharge current has been conducted to generate electric discharge, both electrical discharge passages 12a, 12b are opened to completely interrupt discharge of a charged condenser 17. In addition, a transient current conducted due to inductance formed by the discharge passages 12a, 12b just after the FETs 16a, 16b are switched off flows to a charging condenser 17 through current limiters 21a, 22a on connecting passages 21, 22 to cause a discharge current to steeply rise for an ideal discharge current waveform. Thus, electrical discharge machining can be effected with good surface roughness.

Description

Detailed Description of the Invention Technical Field The present invention relates to electrical discharge machining in which a workpiece is machined into a desired shape by utilizing a discharge phenomenon when a voltage is applied between a workpiece electrode and a discharge electrode. It's about machines.

BACKGROUND OF THE INVENTION Conventionally, there is an electric discharge machine of this type as shown in FIG. The configuration is as follows.

A workpiece 1, such as a workpiece electrode, is placed on an X-axis table 2, and the X-axis table 2 is placed on a Y-axis table 3. The X-axis table 2 is reciprocated in the X-axis direction by an X-axis drive motor 4, and the Y-axis table 3 is reciprocated in the Y-axis direction by a Y-axis drive motor 5.

A wire electrode 6 serving as a discharge electrode is pulled out from a supply reel 7, and is wound up by a take-up reel 8 while being given an appropriate tension.

Then, by applying a pulse voltage such that the voltage between the wire electrodes 6 is at a negative level via the feeder 9.10 between the workpiece 1 and the wire electrode 6, the workpiece 1 and the wire electrode 6 are connected to each other. Electric discharge is generated in the gaps between the two.

As shown in FIG. 2, the electric circuit of this tlil energizing machine is as follows. (hereinafter simply referred to as FET) 16, it is connected to the wire electrode 6, and its positive terminal is connected to the workpiece 1 via the discharge path 12b. Then, when the processing start switch 13 is turned on, the DC power supply 11 charges the charging capacitor 17, and the charging voltage of the charging capacitor 1a is changed to the drive circuit 18.
When the FET 16 is turned on, a gap voltage V is applied to the gap between the workpiece 1 and the wire electrode 6.

At this time, the gap narrows based on the drive of each motor 4.degree. 5, so that discharge is started and a discharge current I flows. Then, after a predetermined time after discharge starts, FETI
After turning on the FETI 6, the drive circuit 18 turns on the FETI 6 again after a period of rest, thereby repeating the electric discharge as shown in FIG. 3 and machining the workpiece 1 into a desired shape. become.

Further, a resistor 19 and a diode 20 are connected between the discharge paths 12a and 12b, so that when the FETI 6 is turned off, the resistor 19 consumes the reactance generated on the discharge path due to the inductance L of the discharge path. ing.

However, the problem here is that φ is the discharge path 12a, 1
Since 2b has an inductance component, the discharge current I is distorted by the resistor 19 as shown by the broken line in FIG.
It has been extremely difficult to obtain an ideal discharge current with a small pulse width and a high peak value.

As a result, ideal surface roughness could not be obtained in electrical discharge machining.

Purpose This invention was made to solve the above problems, and its purpose is to shorten the discharge time, that is, to
It is possible to create an ideal discharge current waveform with a small pulse width and a high peak value, which enables discharge machining with good surface roughness, and when the switching element is turned off, the inductance of the discharge path ) to flow the current generated in the positive electrode side of the charging capacitor, and to provide an electrical discharge machine that can effectively utilize the discharge current for the next discharge.

Structure of the Invention In order to achieve the above object, the present invention applies a voltage between a discharge electrode and a workpiece electrode to generate a discharge in the machining gap between them, and uses the discharge energy to machine the workpiece. In an electric discharge machine, a DC power supply that supplies a voltage for generating a discharge between the two electrodes via a discharge path, and a DC power supply connected to the discharge path between both terminals of the DC power supply and the two electrodes, respectively. , one end is connected between a switching element for opening and closing those paths, one electrode connected to the positive terminal side of the DC power supply, and a switching element connected to a discharge path on that electrode side, and the other a first connection path, the end of which is connected to the negative terminal of the DC power source, and a current regulating element that allows current to flow only in a direction from the negative terminal side toward the one electrode side; One end is connected to the positive terminal side of the DC power supply, and the other end is connected between the other electrode and a switching element connected to the discharge path on that electrode side, allowing current to flow only in the direction toward the positive terminal of the DC power supply. The gist of the invention is an electrical discharge machine characterized by comprising a second connection path to which a current regulating element is connected.

EXAMPLE An example embodying the present invention will be described below with reference to FIG.

For convenience of explanation, in this embodiment, the same parts as in the conventional example are given the same reference numerals, and detailed explanation will be omitted.

In FIG. 4, the discharge paths 12a, 12b are provided with first and second FETIs 6a, i6b as switching elements, and are controlled on/off by drive circuits 18a, 18b to operate the respective discharge paths 12a, 12b. Open and close. In this embodiment, drive circuits 18a and 18b are configured to turn both FETs 16a and 16b on and off in synchronization with each other.
It is controlled by.

The first connection path 21 is wired between the discharge path 12b on the side of the workpiece 1 and the discharge path 12a on the side of the DC power source 11, and a first current regulating element 21 made of a diode is installed on the line.
a is provided to allow current to flow only in the direction from the discharge path 12a to the discharge path 12b.

The second connection path 22 is the discharge path 12a on the wire electrode 6 side.
and the discharge path 12b on the DC power supply 11 side, and a second current regulating element 2 made of a diode is installed on the line.
2a is provided to allow current to flow only in the direction from the discharge path 12a to the discharge path 12b.

A transformer 23 is provided in the discharge path 12b, and is connected to the FET
When a discharge occurs in the gap between the workpiece 1 and the wire electrode 6 in a state where 16a and 16b are turned on, the current flowing through the discharge path 12b is detected. The transformer 23 is connected to the light emitting element 24, and causes the light emitting element 24 to emit light based on the detection. And light emitting element 2
The light outputted from 4 is outputted to the light receiving element 26 via the optical fiber 25 as a discharge occurrence detection signal.

The light receiving element 26 is turned on based on reception of the detection signal,
The on signal is output to a central processing unit (hereinafter simply referred to as CPU) 27.

The CPU 27 includes a read-only memory (ROM>28) and a readable and replaceable memory (RAM) 29, and operates according to a control program stored in the ROM28.

Further, the RAM 29 is configured to store various data and various data from time to time.

Then, the CPU 27 turns off the FETIs 6a and 16b at a predetermined time based on the ON signal from the light receiving element 26, and then controls each of the drive circuits 18' via the switching control circuit 30 to turn on the FETIs 6a and 16b after a predetermined time has elapsed. A control signal is output to the terminals a and 18b, and the discharge is controlled to be repeated at a predetermined period.

Next, the operation of the electric discharge machine configured as described above will be explained.

Now, both FETs 16a and 16b are turned on, and a discharge current flows, and from the state where discharge is occurring, both FETs are turned off.
When T16a and T16b are turned off, the same discharge path 12a-,
12b is opened, charging conte]/The 17 1!1. The power is completely cut off, and F F T 16a, 1
Discharge path 12a immediately after 6b is turned off.

The transient current that flows due to the inductance of 12b flows to the charging capacitor 17 through the first and second current regulating elements 21a and 22a of the first and second connection paths 21 and 22, so the fall of the discharge current becomes steep and ideal. In other words, the discharge time can be shortened and discharge machining with good surface roughness can be performed. Furthermore, since the transient current accumulates positive charge in the charging capacitor 17, it is possible to reduce the discharge time for the next discharge. Can be used for electric current.

Effects of the Invention As detailed above, this invention applies a voltage between a discharge electrode and a workpiece electrode to generate a discharge in the machining gap between them, and uses the discharge energy to machine the workpiece. In the processing machine, a DC power supply that supplies a voltage for generating a discharge between the two electrodes via a discharge path, and a DC power supply connected to the discharge path between both terminals of the DC power supply and the two electrodes, respectively; One end is connected between a switching element for opening and closing the path, one electrode connected to the positive terminal side of the DC power supply, and a switching element connected to the discharge path on that electrode side, and the other end is connected to the switching element connected to the positive terminal side of the DC power supply. a first connection path connected to a negative terminal of the DC power source and connected with a current regulating element that allows current to flow only in a direction from the negative terminal side toward the one electrode side; A current that has one end connected to the terminal side, and is connected between the other electrode and a switching element connected to the discharge path on that electrode side, and allows current to flow only in the direction toward the positive terminal of the DC power supply. By providing the second connection path to which the regulating element is connected, it is possible to shorten the discharge time, that is, to create an ideal discharge current waveform with a small pulse width and a high peak value. In addition to enabling electrical discharge machining with good roughness, when the switching element is turned off, the current generated by the inductance of the discharge path flows to the positive electrode side of the charging capacitor, making effective use of the discharge current for the next discharge. It has excellent effects.

[Brief explanation of the drawing]

Figure 1 is a perspective view showing the mechanical arrangement of an electrical discharge machine, Figure 2 is an electrical circuit diagram of a conventional electrical discharge machine, Figure 3 is a waveform diagram to explain the discharge cycle, and Figure 4 is a diagram of this electrical discharge machine. FIG. 1 is an electrical circuit diagram of an electrical discharge machine embodying the invention. In the figure, 1 is a workpiece, 4 is an X-axis drive motor, 5 is a Y-axis drive motor, 6 is a wire electrode, 9 and 10 are feeders, 11 is a DC power supply, 12a and 12b are discharge paths, 16a and 16b is a field effect transistor (FET), 21 is a first connection path, 21a is a first current regulating element, 22 is a second connection path,
22a is a second current regulating element, 23 is a transformer, 24 is a light emitting element, and 27 is a central processing unit (CPU). Patent applicant Brother Industries, Ltd. Agent Patent attorney On 1) Hironobu Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] 1. A voltage is applied between the discharge electrode (6) and the workpiece electrode (1) to generate a discharge in the machining gap (D) between them, and the workpiece is machined by the discharge energy. In an electrical discharge machine for machining an object (1), a DC power supply (11) supplies a voltage for generating a discharge between the electrodes (1, 6) via a discharge path (12a, 12b); Both terminals of the DC power supply (11) and both the electrodes (1, 6>
,! = (7) between 17) fim path (12a, 12b) k
- respectively connected and their paths (12a, 12b)
a switching element (16a, 16b) for opening and closing; one electrode (1) connected to the positive terminal side of the DC power source (11); and a discharge path (12b) connected to the electrode (1) side. One end is connected between the switching element (16b) and the other end is connected to the negative terminal of the DC power source (11), and the current flows from the negative terminal side to the one electrode (1) side. A first connection path (21) to which a current regulating element (21a) that only allows flow is connected, one end of which is connected to the positive terminal side of the DC power source (11), and the other electrode (6). A current regulating element that is connected between the switching element (16a) connected to the discharge path (12a) on the electrode (6) side and allows current to flow only in the direction toward the positive terminal of the DC power source (11). (22a)
A second connection path (22) connected to the electric discharge machine.