JPH02274426A - Electric discharge machine - Google Patents

Abstract

PURPOSE:To increase a machining speed by providing a current direction setting means which sets a direction of a current, flowing in a shield, to a direction reverse to the direction of a current flowing in a core wire. CONSTITUTION:A machining current, flowing in a core wire 11 of a coaxial cable 10, is controlled on and off by the first switching means T0 generating surge energy absorbed by a capacitor C1 charged with an electric charge supplied to a shield and controlled by the second switching means T1, and a current in the shield 12 is allowed to flow in a direction reverse to the direction of the current flowing in the core wire 11 by setting means D1, D2. In this way, a machining speed can be increased, and power consumption of machining can be decreased when the machining speed is equal.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to an electrical discharge machine.

[Prior art] As shown in Fig. 4, a conventional electric discharge machine has a power supply PSO.
An electric discharge machining current is supplied to the machining electrode E and the workpiece W via the diode D, the transistor TO1, and the coaxial cable CC.

A power supply device having an electric current IIApso, a diode D, a transistor TO, etc., and a main body of an electric discharge machine having a machining electrode E, a workpiece W, etc. are connected by a coaxial cable CC. This coaxial cable CC reduces the inductance between the power supply device and the electrical discharge machine main body,
Improving processing speed.

[Problems to be Solved by the Invention] In the above-mentioned conventional device, in the electrical discharge machine main body, the work W
There is a part where the and processing electrode E are separated, and the coaxial cable CC cannot be used in this part, and a single wire SW is used in this part. In particular, in the area between the machining electrodes E and the work W, it is necessary to use a single wire SW.

When the machining current flows, induced inductance is generated in the single wire SW, and due to this inductance, the rise of the electric discharge machining current waveform is poor, the discharge current Q peak value is small, and the machining speed is reduced. There's a problem.

Furthermore, in order to increase the processing speed, it is necessary to increase the power supply voltage, which poses a problem of increasing power consumption.

Furthermore, as the overall shape of the electric discharge machine becomes larger, the single wire SW becomes longer, so the machining speed gradually decreases. Therefore, the performance such as the machining speed changes depending on the shape of the electric discharge machine and is not constant. There's a problem.

The present invention can increase the machining speed, reduce the power consumption at the same machining speed, and even if the shape of the electric discharge machine changes, the machining speed remains constant. The purpose is to provide a certain electric discharge machine.

[Means for Solving the Problem] The present invention supplies a machining current from a power source to a machining electrode and a workpiece through a core wire of a coaxial cable, and controls on/off of the machining current flowing through the core wire by a first switching means. The surge energy generated by the first switching means is absorbed by a capacitor, and the charge charged in the capacitor is controlled to be supplied to the shield by the second switching means, so that the current in the shield is made equal to the current flowing through the core wire. It flows in the opposite direction.

[Function] The present invention controls on/off of the processing current flowing through the core wire of the coaxial cable by the first switching means, absorbs the surge energy generated by the first switching means with the capacitor, and absorbs the surge energy charged in the capacitor. The supply of electric charge to the shield is controlled by the second switching means, and the current in the shield is caused to flow in the direction opposite to the direction of the current flowing through the core wire, so the machining speed can be increased, and even if the machining speed is the same, can reduce the power consumption of
Further, even if the shape of the electric discharge machine changes, the machining speed remains constant.

[Example] FIG. 1 is a circuit diagram showing one embodiment of the present invention.

In this embodiment, a coaxial cable 10 having a core wire 11, a shield 12, and an insulating material insulating these is provided in place of the single wire SW of the conventional example. On and off of the current is controlled by the transistor TO, the surge energy generated by the transistor TO is absorbed by the capacitor C1, and the charge charged in the capacitor C1 is controlled to be supplied to the shield 12 by the transistor TI, and the surge energy generated by the transistor TO is controlled to be supplied to the shield 12. Current, core wire 1
The current flows in the opposite direction to the direction of the current flowing in 1.

In other words, connect the core wire of coaxial cable CC to workpiece W,
The shield of the coaxial cable CC and the processing electrode E are connected by the core wire 11 of the coaxial cable IO. Then, the transistor TO turns on the processing current flowing to the core wirework 1.
The capacitor CI absorbs the surge energy generated in the transistor TO, and the transistor Tl
controls supplying the electric charge charged in the capacitor C1 to the shield 12, and is connected so that the direction of the current flowing through the shield 12 is opposite to the current flowing through the core wire 11.

Note that the diodes D1 and D2 are reverse current blocking diodes, and the variable resistor VRI adjusts the amount of current flowing through the shield 12.

Further, the transistor TO is an example of a first switching means that controls on/off of the processing current flowing through the core wire, and the capacitor C1 is an example of a capacitor that absorbs surge energy generated by the first switching means, The transistor T1 is an example of a second switching means that controls supply of the electric charge charged in the capacitor C1 to the shield 12.

Next, the operation of the above embodiment will be explained.

When performing electrical discharge machining on the workpiece W, the transistor TO is configured to apply a discharge pulse between the machining electrode E and the workpiece W according to the state of the machining gap, the material of the workpiece W, the machining speed, the state of the machining fluid, etc. The transistor T1 repeats on and off with the same pulse width and period as this repeat of on and off.

Note that surge energy is generated when transistor TO is turned on, and this surge energy is transferred to capacitor C1.
When the transistor TI is turned on, a current flows through the shield 12 using this surge energy as a power source. The value of this current can be controlled by adjusting variable resistor VRI.

Then, when the pulse of the transistor TO is turned on and discharge is started, a machining current flows from the coaxial cable CC toward the machining electrode E. At this time, the transistor T1 is turned on, so that the shield 12 of the coaxial cable 10 A current flows from the front end 13 to the rear end 14. In other words, the third
As shown in the figure, the direction of the processing current I flowing through the core wire 11 of the coaxial cable 10 and the direction of the current i flowing through the shield 12 are opposite to each other.

At this time, the rising edge of the waveform of the machining current becomes better and steeper than in the conventional example shown in FIG. 4), the peak value of the machining current (2) increases, and the machining speed improves. Furthermore, in order to process at the same speed as the conventional example shown in FIG. 4, the voltage of the power source PSO can be lowered, and therefore power consumption can be reduced.

As mentioned above, the reason why the peak value of the machining current increases by using the coaxial cable 10 instead of the single wire SW is because of the power supply around the machining electrode E! The value of the inductance of l (coaxial cable 10) is the same as that of the single wire S in the conventional example.
This is because the inductance value is smaller than the value of the inductance of W.

Furthermore, the length of the part where single wire SW was conventionally used (the third
By adjusting the axial length Ll of the shield 12 relative to the length shown as L2 in the figure, the inductance value of the part used in place of the conventional single wire SW (the coaxial cable 10 and the single wire part) can be adjusted. can be adjusted. Therefore, in the largest shape electrical discharge machine, the single wire S
It is possible to match the inductance value of the part used in place of W to the inductance value of an electrical discharge machine of another size. This makes it possible to unify the machining speed even if the electric discharge machines have different sizes. Moreover, conventionally, the inductance value of the single wire SW portion was decreased by increasing the number of single wire SWs, but according to the above embodiment, the inductance value can be adjusted without increasing the number of coaxial cables. Gade monkey.

FIG. 2 is a circuit diagram showing another embodiment of the present invention.

In the embodiment shown in FIG. 2, the variable resistor VRI of the embodiment shown in FIG. 1 is omitted.

To increase the value of the current flowing through the shield 12, it is sufficient to increase the value of the capacitor C1, and to decrease the value of the current flowing through the shield 12.

It is sufficient to reduce the value of the capacitor C1, and thereby the value of the current flowing through the shield 12 can be controlled to some extent even if the variable resistor VRI is omitted.

In this case as well, the inductance between the coaxial cable CC and the electrode E is reduced. Therefore, in this case as well, the machining speed can be increased.

Note that the variable resistor VRI can be replaced with a fixed resistor. In addition, a circuit consisting of the coaxial cable 10, variable resistor VRI, transistor T1, diodes DI, D2, and capacitor C1, or a circuit in which variable resistor VRI is omitted, is connected between the core wire of coaxial cable CG and the workpiece W. May be used for

Further, other switching elements may be used in place of the transistors TO and Tl.

Furthermore, the portion connected to the core wire of the coaxial cable CC may be connected to its shield, and the portion connected to the shield may be connected to its core wire.

[Effects of the Invention] According to the present invention, the machining speed can be increased, and at the same machining speed, the power consumption can be reduced, and furthermore, the shape of the electric discharge machine can be changed. This also has the effect of keeping the machining speed constant.

O...coaxial cable, 1...core wire, 2... Shield, 1... Capacitor.

1...Transistor.

Claims (2)

[Claims] (1) An electric discharge machine that supplies machining current from a power source to a machining electrode and a workpiece through the core wire of a coaxial cable consisting of a core wire, a shield, and an insulating material that insulates these, and the current flows to the core wire. The first part controls the on/off of the machining current.
a switching means; a capacitor for absorbing surge energy generated by the first switching means; a second switching means for controlling the supply of electric charge charged in the capacitor to the shield; An electrical discharge machine comprising: current direction setting means for setting a direction opposite to the direction of the current flowing through the core wire; (2) An electrical discharge machine according to claim (1), further comprising a resistor in series with the second switching means.