JPH02274425A - Electric discharge machine - Google Patents

Abstract

PURPOSE:To increase a machining speed by providing the first and second switching means for allowing an electric current, flowing in a shield, to flow in a reverse direction to an electric current flowing in a core wire. CONSTITUTION:A machining current is supplied to a machining electrode E and a workpiece W from a power supply through a core wire 11 of a coaxial cable 10, while an electric current, flowing in a shield 12, is allowed to flow in a reverse direction to the current, flowing in the core wire, by providing the first switching means T0 controlling on and off the machining current, flowing in the core wire 11, and the second switching means T1 controlling on and off the current supplied from the power supply and flowing in the shield 12 of the coaxial cable 10. In this way, a machining speed can be increased.

Description

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

[Conventional technology 1] As shown in Fig. 4, a conventional electrical discharge machine uses 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 including a power supply pso, a diode D, a transistor TO, etc., and an electric discharge machine main body including a machining electrode E, a workpiece W, etc. are connected by a coaxial cable cc. The coaxial cable CC reduces the inductance between the power supply device and the electrical discharge machine main body, thereby improving the machining speed.

[Problem to be solved by the invention J] In the above-mentioned conventional device, the workpiece W is
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 p (flows), inductive inductance is generated in the single wire SW, and due to this inductance, the rise of the discharge machining current waveform is poor, the peak value of the discharge current is small, and the machining speed is reduced. There is a problem.

Furthermore, as the overall shape of the electrical discharge machine becomes larger, ! As the SW becomes longer, the machining speed gradually decreases.Therefore, there is a problem that the machining speed and other characteristics change depending on the shape of the electrical discharge machine and are not constant.

SUMMARY OF THE INVENTION An object of the present invention is to provide an electric discharge machine that can increase the machining speed and maintains a constant machining speed even if the shape of the electric discharge machine changes.

[Means for Solving the Problems] The present invention provides a first switching means for supplying a machining current from a power source to a machining electrode and a workpiece through a core wire of a coaxial cable, and controlling on/off of the machining current flowing through the core wire. and a second controller that controls on/off of the current supplied from the power source and flowing through the shield of the coaxial cable.
A switching means is provided to cause the current flowing through the shield to flow in the opposite direction to the current flowing through the core wire.

[Operation 1] The present invention provides a first switching means for supplying a machining current from a power source to a machining electrode and a workpiece through a core wire of a coaxial cable, and controlling on/off of the machining current flowing through the core wire; A second controller for controlling on/off of the current supplied from the coaxial cable to the shield of the coaxial cable.
Since the current flowing through the shield is caused to flow in the opposite direction to the current flowing through the core wire, the machining speed can be increased, and even if the shape of the electric discharge machine changes, the machining speed can be maintained. 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 them is provided in place of the conventional single wire SW, and an electrical discharge machining current is passed through the core wire 11, and a current is supplied from the power source PSO. A transistor T1 is provided to control on/off of the supplied current flowing through the shield 12,
The current flowing through the shield 12 is caused to flow in the opposite direction to the current flowing through the core wire 11.

Note that the variable resistor VRI is used to adjust the amount of current flowing through the shield 12.

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 10. Then, a current from the power source PSO flows to the shield 12 of the coaxial cable 10 via the diode D and the variable resistor VRI under the control of the transistor T1. And shield 1
The wires 2 are connected so that the direction of the current flowing through the core wire 11 is opposite to the current flowing through the core wire 11.

Further, the transistor TO is an example of a first switching means that controls turning on and off of the machining current flowing through the cores t&11. The transistor T1 repeats on and off in synchronization with the operation of the transistor TO, and is connected to the power supply PS.
Turning on the current supplied from O and flowing through the shield 12,
This is an example of a second switching means for controlling off.

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 one cycle of pulse width, which is the same as the repetition of on and off.

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 IO is opposite to the direction of the current i flowing through the shield 12.

At this time, the rise of the waveform of the machining current I becomes better and steeper than in the conventional example shown in FIG. 4), the peak value of the machining current I increases, and the machining speed improves.

As mentioned above, the reason why the peak value of the machining current I increases by using the coaxial cable 10 instead of the single wire SW is that the power line around the machining electrode E (the coaxial cable 10
0) 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
(length shown as L2 in Ugi), shield 1
By adjusting the axial length Ll of 2, it is possible to adjust the inductance value of the portion (the coaxial cable IO and the single wire portion) used in place of the conventional single wire SW. Therefore, the inductance value of the part used in place of the single wire SW in the largest-sized electrical discharge machine,
It is possible to match the inductance value of electrical discharge machines of other sizes. 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. I can do it.

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

In the embodiment shown in FIG. 2, the transistor TI of the embodiment shown in FIG. 1 is omitted.

Lead wire from the cathode side of diode D to shield 12, shield 12, and variable resistor VR from shield 12
I. The loop from the variable resistor VRI to the ground side of the power source PSO is an example of a loop that is supplied with current from the power source PSO, has a resistor, and allows current to flow through the shield.

In this way, although current always flows through the shield 12, the inductance between the coaxial cable CC and the electrode E is reduced at least when electric discharge is occurring between the electrode E and the workpiece W. 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.

Note that a circuit including the coaxial cable 10, the variable resistor VRI, and the transistor T1, or a circuit in which the transistor TI is omitted may be used between the core wire of the coaxial cable CC and the workpiece W.

Further, other switching elements may be used in place of the transistor TO1T1.

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 even if the shape of the electric discharge machine changes, the machining speed can be maintained constant.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing one embodiment of the present invention. FIG. 2 is a circuit diagram showing another embodiment of the present invention. FIG. 3 is an explanatory diagram of the operation in the above embodiment. FIG. 4 is a diagram showing an example of a conventional electric discharge machine. 0...Coaxial cable, 1...core wire, 2... Shield, TI...Transistor.

Claims (2)

[Claims] (1) An electric discharge machine that supplies a machining current from the amount of electricity 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, which flows to the core wire. The first part controls the on/off of the machining current.
A switching means, and a second switching means for controlling on/off of a current supplied from the power source and flowing through the shield, so that the current flowing through the shield is caused to flow in the opposite direction to the current flowing through the core wire. Characteristic electric discharge machine. (2) 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 a loop that is supplied with current from the power source and has a resistor and that flows current through the shield, An electrical discharge machine characterized in that current flows in the opposite direction to the current flowing through the core wire.