JPH0457618A - Electric discharge machine - Google Patents

Abstract

PURPOSE:To increase a machining speed without interrupting electric discharge by controlling the time length of discharge current for machining via the control of a switching element, and compensating for the delay of the discharge current due to the inductance or the like of a current circuit with discharge current from a resistor and capacitor series circuit. CONSTITUTION:Pulsed discharge current is controlled with the operation of a switching element 4 controlled with a switching element control circuit 41, depending upon voltage between an electrode 1 and a workpiece 2, thereby controlling the current time length of discharge current. Concurrently, resistance and capacitance discharge current is fed from a resistor and capacitor series circuit 7 during a discharge process, thereby compensating for the time delay of discharge current. According to the aforesaid construction, the interruption of discharge machining can be prevented.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an electrical discharge machining device in which the time length of a machining discharge current is controlled and the delay of the machining discharge current due to machining current path inductance is compensated for. be. The apparatus according to the present invention is used, for example, when performing electrical discharge machining such as die-sinking on a workpiece using an electrode made of copper, graphite, etc., and is suitable for finishing work on a workpiece with a large area of 300 mm x 300 mm or more. It is advantageously used in cases etc.

[Prior art and problems to be solved by the invention] Conventionally, in electrical discharge machining equipment, machining current is supplied from a DC power supply to an electrode/workpiece through a machining current path, and a switching element and a current limiter are connected to the machining current path. By inserting a resistor in series and controlling the switching element, the machining discharge current is controlled and a pulsed voltage is applied between the electrode and the workpiece.

However, in this electric discharge machining apparatus, the power supply line, current limiting resistor, and other wiring as the machining current path have inductance, so a current delay occurs due to the inductance, which is necessary to maintain the electric discharge in electric discharge machining. There is a problem in that current cannot be supplied in some cases, and the discharge is interrupted during electrical discharge machining, resulting in deterioration of the electrical discharge machining.

This is a problem that becomes particularly noticeable when electrical discharge machining is performed on a large area or when electrical discharge machining is performed using a small current.

Further, even if an attempt is made to control the time length of the machining discharge current by controlling the switching element, a current delay occurs due to the inductance, so there is a problem that the time length of the machining discharge current cannot be appropriately controlled. There is also.

The main purpose of the present invention is to control the time length of a machining discharge current by controlling a switching element inserted in a machining current path, and to control the time length of a machining discharge current by controlling a switching element inserted in a machining current path. It is an object of the present invention to provide an electric discharge machining apparatus in which machining speed is increased without causing discharge interruption by compensating for delays in machining discharge current due to inductance of a machining current path using discharge current from a series circuit.

[Means and effects for solving the problem] The present invention includes an electrode (1) for performing electric discharge machining on a workpiece (2), and a machining current path (6) through which a machining current is passed through the electrode and the workpiece. a DC power supply (3) to supply; a switching element (4) inserted in the processing current path, which is controlled by a switching element control circuit (41) that operates according to the voltage between the electrode and the workpiece; and a resistor connected in parallel to the gap between the electrode and the workpiece.
A capacitor series circuit (7), wherein the time length of the machining discharge current is controlled by controlling the switching element, and the inductance, etc. of the machining current path is controlled by the discharge current from the resistor/capacitor series circuit. Provided is an electrical discharge machining apparatus characterized in that a delay in a machining discharge current caused by a machining discharge current is compensated for.

In the apparatus according to the present invention, the pulsed machining current is controlled according to the voltage between the electrode and the workpiece by the operation of the switching element controlled by the switching element control circuit, and the current time length of the machining current is controlled. Ru. At the same time, during discharging, a resistor/capacitor discharge current is supplied from the resistor/capacitor series circuit to compensate for the time delay of the discharge current. This prevents the electrical discharge machining from being interrupted.

〔Example〕

An electric discharge machining apparatus as an embodiment of the present invention is shown in FIG. FIG. 2 shows the voltage and current waveforms in the electrical discharge machining apparatus shown in FIG. The electrical discharge machining apparatus shown in FIG. 1 includes an electrode 11 that performs electrical discharge machining on a workpiece 2, and a DC power supply 3 that supplies a machining current to the electrode and workpiece through a machining current path 6.
, and a transistor 4 as a switching element inserted into the processing current path 6. A switching element control circuit 41 is connected to the gate of the transistor 4 .

The switching element control circuit 41 detects the voltage between the electrode and the workpiece, and controls the transistor 4 so that the processing pulse voltage is controlled according to the detection result.

A current limiting resistor 5 is inserted into the machining current path 6.

Inductance existing in the machining current path, current limiting resistor, other wiring, etc. is expressed as an inductance 61 connected in series to the machining current path 6.

In the electric discharge machining apparatus shown in FIG. 1, the electrode/workpiece 1.
A series circuit 7 consisting of a resistor 71 and a capacitor 172 is connected in parallel to the gap between the two.

In the electric discharge machining apparatus shown in FIG. 1, the pulsed machining current is controlled according to the voltage between the electrode and the workpiece by the operation of the switching element 4 controlled by the switching element control circuit 41, and the current of the machining current is The length of time is controlled. At the same time, during discharging, a resistance/capacitance discharge current is supplied from the resistance/capacitance series circuit 7, and time delay of the discharge current is compensated for. This prevents the electrical discharge machining from being interrupted.

Maximum value of resistance/capacitance discharge current for this compensation.

and the current time Tci is the voltage between the electrode and the workpiece E,
The resistance and capacitance in the resistance/capacitance series circuit are R, respectively.
When C, it is expressed by the following relational expression.

IC= (1) Tc1=C
R(2) In the electric discharge machining apparatus shown in FIG. 1, the voltage between the electrode and the workpiece is set to the waveform (1) shown in FIG. Waveform (1
), the switching element 4 is controlled so that the period T1 in which the inter-electrode voltage is in a decreasing state is constant.

The current flowing through the power supply line as a machining current path has a waveform (2) in FIG. The rising period T of this feeder current
dI is the inductance of the machining current path, and when the resistance value of the current limiting resistor 5 is R1, T a i = L /
It is blessed with Rh. That is, Tdl for the current
It is shown that this results in a time delay of . If this state continues, the current during discharge will decrease due to this time delay, and if the current decreases below the discharge sustaining current, there is a possibility that the discharge will be interrupted.

In the electric discharge machining apparatus shown in Fig. 1, the waveform shown in Fig. 2 (
3), a resistance/capacitance discharge current for compensation of the maximum value IC1 current time Tci is supplied.

As a result, (3) CR discharge current is superimposed on (2) feeder current in Figure 2, and the second
The current shown in (4) total discharge current in the figure will flow.

〔Effect of the invention〕

According to the present invention, the time length of the machining discharge current is controlled by controlling the switching element inserted in the machining current path, and the resistor connected in parallel to the gap between the electrode and the workpiece
The discharge current from the series circuit of the capacitors compensates for the delay in the machining discharge current due to the inductance of the machining current path.
It is possible to obtain an electrical discharge machining device with increased machining speed without causing electrical discharge interruption.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an electrical discharge machining apparatus as an embodiment of the present invention, and FIG. 2 is a diagram showing voltage and current waveforms in the electrical discharge machining apparatus of FIG. 1. (Explanation of symbols) 1... Electrode, 2... Workpiece, 3...
・DC power supply, 4... switching element, 41
... Switching element control circuit, 5... Current limiting resistor, 6... Processing current path, 61... Inductance, 7... Resistance/capacitance series circuit, 71... Resistor, 72... capacitor.

Claims (1)

[Claims] 1. Electrode (1) for performing electric discharge machining on a workpiece (2)
, a DC power source (3) that supplies a machining current to the electrode/workpiece through a machining current path (6), a switching element (4) inserted in the machining current path, and a switching element (4) that connects the electrode/workpiece with the machining current. a switching element control circuit (41) that operates according to the voltage of the electrode, and a resistor connected in parallel to the gap between the electrode and the workpiece.
A capacitor series circuit (7), wherein the time length of the machining discharge current is controlled by controlling the switching element, and the inductance, etc. of the machining current path is controlled by the discharge current from the resistor/capacitor series circuit. An electric discharge machining apparatus characterized in that a delay in a machining electric discharge current due to an electric discharge is compensated for. 2. The electric discharge machining apparatus according to claim 1, wherein the resistance value and the capacitance value of the resistor/capacitor constituting the resistor/capacitor series circuit (7) are respectively variable.