JPH089125B2 - Power supply for electrical discharge machining - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a wire electric discharge machining pulse power supply device capable of increasing a machining depth in finishing machining in wire cut electric discharge machining.

[Conventional technology]

In wire-cut electric discharge machining, a repulsive force that impedes its progress acts on the wire electrode due to electric discharge. For this reason, a deviation occurs between the position of the wire electrode indicated by the NC device or the like and the actual position of the wire electrode, and the shape accuracy of the workpiece is reduced.

Therefore, when machining a work piece that requires high precision, after roughing the work piece to a size larger than the finished dimension, a finishing process called a second cut is performed to obtain the required size and surface roughness. It has been finished to the best. Roughing is performed so that the finished dimension at this time is generally several μm.

As a machining electrode for performing the finishing machining, there is, for example, a power supply device for electric discharge machining disclosed in Japanese Patent Laid-Open No. 61-4620.

In this power supply device for electric discharge machining, a pulse voltage of both positive and negative polarities is generated based on the pulse oscillated from a single oscillator, applied to the machining gap, and the average voltage between the poles is set to zero while unidirectional. Since the processing is performed by the voltage, it is possible to prevent the deterioration of the precision of the processed surface and the electrolytic corrosion due to the electrolytic current.

[Problems to be Solved by the Invention]

However, since positive and negative voltages are applied alternately, the machining down time becomes long and the machining efficiency is reduced.

Further, when the oscillation frequency of the oscillator is increased, there is a problem that the voltage applied to the machining gap becomes insufficient and the discharge does not occur.

An object of the present invention is to provide a power supply device for electric discharge machining, which prevents deterioration of machining surface accuracy and electrolytic corrosion due to electrolytic current and enables high-efficiency finish machining.

[Means for solving the problem]

The inventor has paid attention to the fact that if the machining pause time is shortened and the dischargeable time is lengthened, the number of effective discharges between the wire electrode and the workpiece is increased and the machining efficiency is improved. Also,
Experiments have shown that the pulse width of the voltage applied to the machining gap is 10
It was found that the electrolytic current does not increase if the voltage application is interrupted after the voltage is applied between the wire electrode and the workpiece for 0 μsec or less.

A configuration of the present invention for realizing such processing conditions will be described with reference to FIGS. 1 and 2 corresponding to the embodiment.

1 is a work piece. Reference numeral 2 is a wire electrode which holds a predetermined processing gap with the workpiece 1. Reference numeral 4 denotes a transistor, which applies a negative pulse voltage to the machining gap. Reference numeral 7 denotes a transistor, which applies a positive pulse voltage to the machining gap. 9 is a low frequency pulse oscillator. 10 is a high frequency pulse oscillator. Reference numeral 11 is an inverter, which is connected to the low-frequency pulse oscillator 9. An AND circuit 12 has one input terminal connected to the high frequency pulse oscillator 10, the other end connected to the inverter 11, and an output terminal connected to the base side terminal of the transistor 4.
Reference numeral 14 is a NAND circuit, one end of the input terminal is connected to the high frequency pulse oscillator 10, the other end is connected to the low frequency pulse oscillator 9, and the output terminal is connected to the base side terminal of the transistor 7.

[Action]

Then, the inverter 11 outputs an inverted waveform C of the output waveform B of the low frequency pulse oscillator 9. AND circuit 12 has waveform C
And the AND condition of the output waveform A of the high frequency pulse oscillator 10 is taken, and the transistor 4 is turned on and off by the output waveform D,
The voltage of the waveform F on the collector side of the transistor 4 is generated. On the other hand, the NAND circuit 14 takes the NAND condition of the output waveform B of the low-frequency pulse oscillator 9 and the output waveform A of the high-frequency pulse oscillator 10, turns on / off the transistor 7 with the output waveform E, and applies the voltage of the waveform G to the collector side of the transistor 7. To generate. Then, the voltage waveform H obtained by adding the waveform F and the waveform G
Is applied to the machining gap.

This waveform H is shaped into a rectangular shape with the cycle of the waveform B having a long cycle due to the inductance and stray capacitance of the current-carrying cable or the like, so that the time ta that is equal to or higher than the dischargeable voltage E _A can be long. Therefore, the dischargeable time is long and the number of effective discharges can be increased, so that the machining efficiency is improved.

〔Example〕

1 and 2 are views showing an embodiment of a power supply device for electric discharge machining of the present invention.

Reference numeral 1 denotes a workpiece, which is installed on a table (not shown) that moves on the XY axis plane by a driving device such as an NC device. Reference numeral 2 denotes a wire electrode, which holds a predetermined machining gap between the workpiece 1 and the work piece 1 through water as a machining liquid. Reference numeral 3 denotes a DC power source, the positive electrode side of which is connected to the workpiece 1
A voltage is applied between the wire electrode 2 and the wire electrode 2. Reference numeral 4 denotes an NPN type transistor, the emitter side of which is connected to the negative side of the DC power supply 3 to turn on and off the voltage E ₁ of the DC power supply 3. A current limiting resistor 5 is inserted in series between the collector side of the transistor 4 and the wire electrode 2. 6 is a DC power supply, the negative electrode side is connected to the workpiece 1, and is connected in parallel with the DC power supply 3,
A voltage having a polarity opposite to that of the DC power supply 3 is applied between the workpiece 1 and the wire electrode 2. 7 is a PNP type transistor, the emitter side is connected to the positive side of the DC power supply 6, and the voltage of the DC power supply 6
Control E _{2 on} and off. A current limiting resistor 8 is inserted in series between the collector side of the transistor 7 and the wire electrode 2. 9 is a low frequency pulse oscillator. 10 is a high frequency pulse oscillator. Reference numeral 11 is an inverter, which is connected to the low-frequency pulse oscillator 9. An AND circuit 12 has one input terminal connected to the high-frequency pulse oscillator 10, the other end connected to the output terminal of the inverter 11, and the output terminal connected to the base side of the transistor 4. A drive circuit 13 is inserted in series between the AND circuit 12 and the base side of the transistor 4. 14 is a NAND circuit, one end of the input terminal is connected to the high frequency pulse oscillator 10 in parallel with the AND circuit 12, and the other end is connected to the low frequency pulse oscillator 9 in parallel with the inverter 11.
Moreover, the output terminal is connected to the base side of the transistor 7. A drive circuit 15 is inserted in series between the NAND circuit 14 and the base side of the transistor 7.

With such a configuration, the high frequency pulse oscillator 10 outputs a pulse having a short cycle like the waveform A as shown in FIG.
On the other hand, the low-frequency pulse oscillator 9 outputs a pulse having a long cycle like the waveform B. The inverter 11 inverts the waveform B,
The signal of waveform C is output. The AND circuit 12 takes the AND condition of the waveform A and the waveform C, and outputs the signal of the waveform D. The drive circuit 13 amplifies the signal of the waveform D and the transistor 4
Turn on and off. Then, the voltage on the collector side of the transistor 4 has a waveform F. On the other hand, the NAND circuit 14 takes the NAND condition of the waveform A and the waveform B and outputs the signal of the waveform E. The drive circuit 15 amplifies the signal of the waveform E to turn on / off the transistor 7. Then, the voltage on the collector side of the transistor 7 has a waveform G. The pulse voltages of the waveform F and the waveform G are added through the current limiting resistance 5 and the current limiting resistance 8 and then applied to the machining gap. Here, the waveform of the voltage applied to the processing gap becomes a waveform H due to the inductance and stray capacitance of the energizing cable. Then, electric discharge is generated in the machining gap, and the workpiece 1 is machined. Then, when an electric discharge occurs, a machining current of waveform I flows through the machining gap,
The voltage in the machining gap drops and becomes a waveform J.

In the period of the waveform H is long period waveform B, because it is shaped pulse voltage in a rectangular shape, a dischargeable voltage E _A above in which dischargeable time t _a is long, can increase the number of effective discharge machining, The processing efficiency can be improved.

 A specific experimental example in the above embodiment will be shown below.

Workpiece 1: Tool steel SKD11, HRC60 ℃ hardened material, plate thickness 50mm Wire electrode 2: Brass 0.2mmφ DC power supply 3: 50V DC power supply 6: 50V Low frequency pulse oscillator 9: Cycle 80μsec High frequency pulse oscillator 10: Cycle 0.25 Under the condition of μsec, the same quality as the conventional processing roughness (processing surface roughness 0.8
(μmRmax, drum amount 5μm or less)
A processing amount of 2 μm (0.5 μm in the past) was obtained at 3 mm / min.

〔The invention's effect〕

According to the present invention, in finishing machining of wire cut electric discharge machining, a rectangular pulse voltage having a long bipolar period is applied to the machining gap. It is possible to improve the processing efficiency by increasing the number of.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of a power supply device for electric discharge machining of the present invention, and FIG. 2 is a time chart for explaining its operation. 1 ... Workpiece, 2 ... Wire electrode, 4 ... Transistor, 7
... Transistor, 9 ... Low frequency pulse oscillator, 10 ... High frequency pulse oscillator, 11 ... Inverter, 12 ... AND circuit, 14 ...
Nando circuit.

Claims (1)

[Claims] 1. Machining formed between a wire electrode and a workpiece by generating a negative pulse voltage by turning on and off a first switching element and generating a positive pulse voltage by turning on and off a second switching element. In a power supply device for electrical discharge machining that applies a positive and negative pulse voltage alternately to a gap to generate an intermittent discharge, a high-frequency pulse oscillator is provided, a low-frequency pulse oscillator is provided, and high-frequency pulse and low-frequency pulse NAND conditions are set. An electric discharge machining is provided, in which a NAND circuit for activating the second switching element is provided, and an AND circuit for activating the first switching element by taking an AND condition of a high frequency pulse and an inverted low frequency pulse is provided. Power supply.