JP3336110B2 - Power supply for electric discharge machine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply for an electric discharge machine, and more particularly to a power supply for an electric discharge machine having a simple structure and improved machining efficiency.

[0002]

2. Description of the Related Art In an electric discharge machine, a high voltage is applied between an electrode and a work from an auxiliary power supply to make a discharge state between the electrode and the work (hereinafter referred to as a gap), and then a large current is supplied from a main power supply. The workpiece is processed by supplying a processing pulse.

The switching from the main power supply to the power supply after the interelectrode discharge by the power supply from the auxiliary power supply is performed by a switching element such as a transistor element. The structure and operation of this type of electric discharge machine are described in, for example, Japanese Patent Publication No. 46-24678 / FIG.
This is described with reference to the drawings, and a simplified circuit diagram thereof is shown in FIG.

In FIG. 6, first, the transistor Tr1 is turned on and the transistor Tr2 is turned off, and the negative terminal of the auxiliary power supply VS is connected to the electrode E via the resistor R1 and the diode D for preventing interference (backflow prevention). Then, by connecting the plus terminal of the auxiliary power supply VS to the work W, a discharge is generated between the electrodes. When this inter-electrode discharge is detected by a detection circuit (not shown), the transistor Tr2 is turned on to connect the negative terminal of the main power supply VM for supplying a large current for electric discharge machining to the electrode E via the resistor R2. The main electric current for machining is supplied between the poles to perform electric discharge machining.

[0005] In this configuration, after the discharge between the poles is started by the auxiliary power supply VS, until the stable electric discharge machining is enabled by the main power supply VM, the switching operation time of the transistor and the inductance component of the power supply line and the like are required. Thus, there is a delay time of several tens to several hundreds of nsec. During this period, a sustain current for maintaining the discharge state between the electrodes is supplied from the auxiliary power supply VS. But,
The auxiliary power supply VS generally has a small capacity and cannot supply a sufficient discharge maintaining current, and sometimes the discharge is interrupted, resulting in a reduction in machining efficiency. Further, if the current capacity of the auxiliary power supply is increased and the discharge by the auxiliary power supply is continued, the discharge time becomes longer, and when the electrode E is a wire electrode, the wire electrode is melted, which may cause disconnection.

Therefore, a series circuit of a capacitor and an inductance is connected in parallel between the electrode and the work (between the poles) so that the gap between the electrodes is discharged by the auxiliary power supply and the supply of the sustaining current is charged by the auxiliary power supply. A device for preventing interruption of the discharge from the discharge between the electrodes to the supply of the machining current from the main power supply is disclosed in Japanese Patent Publication No. 5-92.
No. 09 discloses this with reference to FIGS. 1 to 6 of the publication.

FIG. 7 is a configuration diagram of a main part of this type of electric discharge machine, in which a series circuit of a capacitor C and an inductance L is connected in parallel between an electrode E and a work W.
By the operation of the transistor Tr1 operated by N, the auxiliary power supply VS is connected to the resistor R1, the diode D1 and the power supply cable 11
, And charges the capacitor C of the series circuit. The control circuit 10 detects the detection lines 12 and 1
3, when the inter-electrode discharge is detected, the transistor Tr2 is turned off.
N, the main power supply VM is connected to the resistor R2 and the diode D2.
Then, the electric discharge machining is performed by supplying the voltage between the poles via the power supply cable 11. During the delay time from the detection of the discharge by the auxiliary power supply to the supply of the current from the main power supply, the energy stored in the capacitor C is supplied between the poles as the discharge sustaining current. Since the current sustaining current capacity from the capacitor C has a sufficient capacity for sustaining the discharge, the above-mentioned problem of the circuit of FIG.

FIG. 8A shows an equivalent circuit of a power supply circuit using such a series circuit of inductance and a capacitor (resistance r of the circuit). FIG. 8 (B). FIG. 8 (A)
In FIG. 7, the conduction and non-conduction state between the electrode E and the work W is repeated by the discharge, so that the switch is shown. As shown in FIG. 8B, the discharge maintaining current supplied from the capacitor changes in a sine wave shape.

[0009]

As described above, the power supply device of the conventional electric discharge machine requires an auxiliary power supply for inter-electrode discharge and a main power supply for electric discharge machining.

In addition, a series circuit of a capacitor and an inductance is connected in parallel between the poles, the capacitor is charged when the gap is opened by the auxiliary power source, and the energy charged in the capacitor is discharged at the same time as the discharge between the poles as a discharge maintaining current. To supply.

However, such a power supply device for an electric discharge machine requires not only two power supplies but also a series circuit of an inductance and a capacitor for charging a discharge maintaining current. 8 (B)
As shown in (1), it becomes a sine wave, and it takes time from the start of the current flow to the peak. For this reason, the processing performance is limited.

Accordingly, an object of the present invention is to eliminate the need for an auxiliary power supply for starting electric discharge, to use only a main power supply for electric discharge machining, and to realize a simple configuration and a sharp rise in current simultaneously with the start of electric discharge. Another object of the present invention is to provide a power supply device of an electric discharge machine which enables highly efficient electric discharge machining.

[0013]

In order to solve the above-mentioned problems, a power supply apparatus for an electric discharge machine according to the present invention supplies a voltage from a power supply between an electrode and a work through a switching circuit to connect the electrode to the work. In the power supply device of an electric discharge machine for generating electric discharge and supplying electric discharge machining current to perform electric discharge machining of the work, a predetermined one connected in parallel between the electrode and the work via a resistor for impedance matching on one end side. It comprises at least one long coaxial cable.

[0014]

In the present invention, one end of at least one coaxial cable of a predetermined length is connected in parallel between the electrode and the work via a matching impedance, and the electrode and the work are discharged by one power supply. Thereafter, an electric discharge machining current is supplied between the electrode and the work by the energy stored in the coaxial cable.

[0015]

Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a main part circuit configuration diagram showing an embodiment of a power supply device of an electric discharge machine according to the present invention.

In this embodiment, only one power supply 2 is required, no auxiliary power supply is required, and the ON / O
Power is supplied between the poles via the resistor R by the FF operation. That is, in this embodiment, the resistor R, the transistor 3 and the power supply 2 are connected in series between the poles, and a negative voltage is supplied to the electrode (E) 4 and a positive voltage is supplied to the work (W) 5. The transistor 3 is ON / OFF controlled by the control unit 6.
Between the poles, a coaxial cable 1A whose one end is open via matching impedances ZA and ZB.
And 1B are connected in parallel. The number of coaxial cables connected in parallel between the poles can be set arbitrarily according to the magnitude of the supplied current, and a matching impedance is connected to each coaxial cable to be connected.

Coaxial cables 1A, 1 open at one end
B, as an equivalent circuit, is represented by a distributed constant circuit including an inductance component L and a capacitance component C, as shown in FIG. 3, and has a signal delay function. Therefore,
When the voltage from the power supply 2 is supplied between the poles, the voltage is supplied and charged to the coaxial cables 1A and 1B until the gaps reach a discharge state.
Pulses for electric discharge machining are supplied from A and 1B to perform electric discharge machining.

FIGS. 4A and 4B are a circuit diagram and a waveform diagram for explaining the function of the coaxial cable in this embodiment. One end of the coaxial cable 1 having a length h whose other end is open is connected via a matching impedance Z to a switch SW (between the electrode E and the work W) which simulates a discharge operation between the electrodes and a non-discharge operation by a switch operation. Connected in parallel. When the switch SW is OFF, the capacitance of the coaxial cable is charged from the power supply V via the resistor R and the matching impedance Z. By simulating the discharge state between the electrodes, the switch S
As soon as W is turned on, the coaxial cable 1
A pulse current i as shown in (B) is supplied to the switch SW. In FIG. 4, the magnitude of the supplied current i is
The pulse width (duration) t is determined by the characteristic impedance and the number of coaxial cables connected in parallel, and the pulse width (duration) t is proportional to the length h of the coaxial cable.

That is, the coaxial cable 1 is represented by a distributed constant circuit of an inductance and a capacitor, functions as a capacitor in terms of static characteristics, functions as a signal delay circuit for a high-speed signal, and includes a transistor 3. As long as it is turned on and not yet discharged, it functions as a capacitor and is charged. At the same time as the discharge occurs between the poles, the gap acts as a load, and the energy stored in the coaxial cable 1 is released. Since the voltage is sequentially sent from the open end side of the coaxial cable 1 to the load side, the voltage at the output end is constant while the voltage remains in the coaxial cable.
A square wave current as shown in FIG.

FIG. 2 shows an operation timing chart of the circuit configuration section of this embodiment shown in FIG. In response to the ON operation of the transistor 3, as shown in FIG. 4A, a voltage that rises steeply from the power supply 2 via the resistor R is supplied to the gap. When the gap starts to be discharged at the timing t1 of the voltage supply to the gap, an electric discharge machining current having a pulse width tw as shown in FIG.
Discharge is performed.

FIG. 5 shows an applied embodiment of the present invention, in which a voltage supply cable for charging the capacitance of a coaxial cable is also used as a coaxial cable, and the operation and function are the same as those in FIG.

As described above, when the present invention is applied, the machining performance of the wire electric discharge machine is improved, and the machining functions of the non-ferrous metal and the general finishing in the die sinking electric discharge machine are improved. In particular, since the time from the start of electric discharge to the supply of machining current is greatly reduced, when used in a wire electric discharge machine, the disconnection of the wire electrode is reduced, the impact coefficient can be increased, and the machining speed is improved. I do.

[0023]

As described above, according to the power supply device for an electric discharge machine according to the present invention, only one power supply is required, and the time from the discharge to the supply of the machining current can be greatly reduced, so that the configuration is simplified. Thus, stable and high-speed processing can be performed.

[Brief description of the drawings]

FIG. 1 is a main part circuit configuration diagram showing one embodiment of a power supply device of an electric discharge machine according to the present invention.

FIG. 2 is an operation timing chart of a circuit configuration unit of the present embodiment.

FIG. 3 is a diagram for explaining functions and operations of the coaxial cables 1A and 1B having one open end used in the embodiment.

FIG. 4 is a circuit diagram and a waveform diagram for explaining the operation of the coaxial cable.

FIG. 5 is a main part circuit configuration diagram of another embodiment according to the present invention.

FIG. 6 is a configuration diagram of a power supply device of a conventional electric discharge machine.

FIG. 7 is a configuration diagram of a power supply device of another conventional electric discharge machine.

8 is a diagram for explaining the operation of the device shown in FIG.

[Explanation of symbols]

 1, 1A, 1B Coaxial cable 2 Power supply 3 Transistor 4 Electrode 5 Work 6 Control unit ZA, ZB Matching impedance

Claims (2)

(57) [Claims] An electric discharge machine which supplies a voltage from a power supply between an electrode and a work via a switching circuit to generate a discharge between the electrode and the work, and supplies an electric discharge machining current to perform an electric discharge machining of the work. A power supply device for an electric discharge machine, comprising at least one coaxial cable of a predetermined length connected in parallel between the electrode and the work via a resistor for impedance matching on one end side. . 2. The method according to claim 1, wherein the power supply is a single power supply, and after a discharge is started between the electrode and the work by the power supply, a discharge machining current is supplied between the electrode and the work by energy stored in the coaxial cable. The power supply device for an electric discharge machine according to claim 1, wherein