JPS5848292B2 - Wire power supply - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in an apparatus for processing a wire electrode by winding it up with a predetermined tension and moving it while passing current between the wire electrode and a workpiece.

The electrode wire is usually a thin wire with a wire diameter of about 0.05 to 0.3 mm, and is bent at 70 mm to prevent lateral vibration.
A tension of about 0 to 800 g is applied to move the workpiece from one side to the other, and a machining fluid such as water or oil is supplied to the gap where the workpiece faces the workpiece, and electricity is applied to process the electrode or the workpiece. By applying a two-dimensional machining feed in a plane perpendicular to the direction of movement of the wire according to the progress of machining, various shapes can be cut, extracted, etc.

This wire electrode processing has the effect of making it easy to process various shapes with a single wire, but as mentioned above, extremely thin wires are used for the wire electrodes, and a considerable amount of tension is applied to them. It has the disadvantage of being easily cut.

Furthermore, compared to when no load is applied, during machining, the tensile strength is lowered due to Joule heat due to current flow, electric discharge, etc., and local pressure is applied, so that yarn edge breakage is more likely to occur.

The present invention was proposed to prevent this wire from breaking.

That is, when a predetermined tension is applied to the wire, it elongates in accordance with the tension, and this elongation is detected and used as a signal to control the tension.

The present invention will be explained below with reference to an example of the drawings. In FIG. 1, a wire 1 is fed out from a reel 2 by a wire electrode, passes through a plurality of guide rollers 4 on the way, and is wound onto a take-up reel 3.

5 is a drive roller that winds the wire 1 and drives it in the direction of movement; 6 is a pinch roller; 7 is its drive motor; 8 is a brake roller provided on the feeding reel 2 side of the wire electrode 1; for example, a magnetic brake is used; 9 is a vinyl roller, 10 is a brake excitation coil, and 11 is a workpiece, which is fixedly attached to a table 12 to which two-dimensional machining feed in X and Y is given by NC signals, copying signals, etc., and wire electrode 1 and Electricity is supplied to the opposing machining gap from a machining power source connected to terminal B.

14 is an encoder that converts and detects the rotation of the drive roller 5 into a pulse signal, 15 is an encoder that converts the rotation of the brake roller 8 into a pulse signal, 16 and 17 are Schmitts that digitally detect the output of the encoder, and 18 is an up/down counter. , the signal from the Schmitt 16 is used to count up, and the signal from the other Schmitt 17 is used to count down.

Reference numeral 19 denotes an oscillator that drives and controls the pulse motor 7 by passing clock pulses of a constant frequency through a gate circuit 20.

Reference numeral 21 denotes a discrimination device that detects and discriminates the state of the machining gap using, for example, the average voltage of the gap, and this discrimination output and the counter 18
The gate circuit 20 is turned on and off by the AND gate 22 output, and the drive motor 7 is controlled.

23 is a knot gate. 〇Figure 2 shows the specific structure of the brake roller 8.
A magnet 25 is attached to a disc 24 directly connected to the brake roller shaft.
When the magnet coils 10 are made to face each other and the magnet coils 10 are constantly excited, an electromagnetic force is applied by the eddy currents induced in the discs to perform brake operation.

Machining is performed by applying a machining pulse from a terminal 13 to a gap between a moving wire electrode 1 and a workpiece 11 attached to a machining table 12, and machining is performed by electric discharge or electrolytic action. The desired shape is processed by controlling the motor by applying a processing feed signal.

During processing, the wire electrode 1 is sent from a reel 2, is wound onto another reel 3, and a predetermined tension is applied by the winding force of the drive roller 5 and the braking action of the brake roller 8, and in this state, the wire electrode 1 is moved to the other reel 3. By passing through the opposing portions of the wire 11, bending and lateral vibration of the wire are prevented and precision machining is performed.

This wire tension can be arbitrarily adjusted by controlling the rotational speed of the drive roller 5 by the motor 7 and controlling the braking force of the brake roller 8. Even if the number of rotations of the roller 5 is increased, the tension can be increased.

Conversely, if the excitation of the excitation coil 10 is weakened, the oscillation frequency of the oscillator 19 is lowered, and the rotational speed of the roller 5 is lowered, the tension is weakened, and if this control is kept constant, the tension can be kept constant.

For the wire electrode 1, a wire made of Cu, W, Co, Mn, etc. with a wire diameter of about 0.05 to 0.3 mm is usually used. For example, if a 0.2 mm diameter Cu wire is used, the length is 1.2 m. When a tension of 700 g is applied to the material, an elongation of about 2.4 mm occurs.

The elongation of this wire increases proportionally when the tension is increased, and eventually it breaks, but this is also different when no current is applied and when it is energized, and it also increases proportionally when current is applied. .

Figure 3 shows 10
When processing 855C material with a thickness of 7 nm, the tension was 7 at the beginning.
Adding 50g shows an elongation of 3.5 times per meter of length,
This is an experimental graph when the tension was controlled so that this elongation remained constant even with changes in current.

In other words, this is controlled so that the tension is applied to a value that keeps the elongation constant, and when no current is applied, the tensile strength is approximately 3 3 k!
What was 97ml was approximately 20k with an average processing current of 3A.
It can be seen that the tensile strength decreases to as low as 15 to 16 kg/mrlt, and that it is cut when the tensile strength reaches about 15 to 16 kg/mrlt.

Therefore, when processing while keeping the tension constant, it is necessary to control the tension by using the elongation of the wire as a detection signal in order to prevent the wire from breaking.

When the tension is maintained constant, the difference between the number of rotations of the drive roller 5 and the number of rotations of the brake roller 8 corresponds to the elongation of the wire. The signal is applied to the counter 18 through the Schmitt 17 and counted up and down to produce a counter output proportional to the elongation.

The output of the counter 18 is "0" while the count number is low.
On the way, knot 23 is inverted, signal 11'' is added to AND game 22, and gate 20 is turned on, so oscillator 1
Since the clock pulse of 9 is applied to the motor 7 and rotates at a constant speed, a constant tension is applied between the motor 7 and the constant brake 8. When the counter 18 counts up to the preset value, a signal 61 is generated. Therefore, when the elongation of the wire exceeds a certain value, the counter 18 outputs a signal "'1".
is output, which is inverted at knot 23 and is applied to AND gate 2
A signal "O" is applied to the signal "O", and the AND output becomes "0", which turns off the gate 20 and stops the drive motor 7.

If the tension decreases due to this instantaneous stop of the motor 7, the elongation will also decrease, and the output of the counter 18 will become n O n. Since the signal N I 11 is applied to the AND gate 22, the gate 20
is turned on and the motor 7 starts driving again.

Therefore, by setting the preset value of the counter 8 to a value that has a margin before the amount of elongation breaks depending on various conditions such as the material of the wire electrode 1, the wire diameter, and the guide gap, the set value can be exceeded. Since the tension is instantly reduced and controlled, wire breakage can be prevented and stable machining can be continued.

That is, for example, with a 0.2 mwφCu wire, the moving speed is 1
In the case of motor control of 2 ml mm, tension 700 g, and 1 pulse of 300 μs, approximately 0. 7 8 @se ■ Tension can be controlled in response to speed, and the detection accuracy of elongation by the encoder is approximately ±
It can be detected with an accuracy of 0.05 mm, and when the tension is controlled to be weakened to 1 when the elongation exceeds the set value, wire breakage can be completely prevented.

In general, wire breakage can be prevented by providing a response speed of 3 to 5 mse (l) or less.

During processing, the tension will vary depending on the thickness of the workpiece and the current flow.
Although it varies between 5 g and 716 g, stable processing can be performed by not controlling this intermittent fluctuation, but by determining and controlling when there is continuous elongation of the wire.

Furthermore, as shown in the example in Figure 3, even if the elongation of the wire is constant, the tensile strength decreases due to the processing current, so when the current increases beyond a certain value, quick tension control is required before the elongation of the wire occurs. However, this is detected by the discrimination device 21.

That is, the discriminating device 21 discriminates the gap voltage, and when the current abnormally increases for some reason, the gap voltage decreases, so this is discriminated and detected.

Normally, during normal machining, the output signal is "1" and the AND gate 2
In addition to 2, when the abnormal state is determined, the signal II
0 to 11, the AND gate 22 output becomes "O", and the gate 20 is immediately turned off and the drive motor 7 is turned off.
to stop.

In this way, processing is performed while detecting and determining the state of the wire elongation and processing gap (changes in current, voltage, etc.), and when an abnormality exceeds the set value by AND combination of both signals, tension control is performed. Can be processed while completely preventing the wire from breaking.

Of course, it is also possible to detect the elongation of the wire electrode in an analog manner and use this as a signal to control the tension in an analog manner, or to perform analog control of the tension by detecting the gap state in an analog manner.

In FIG. 4, reference numeral 26 denotes a device for analog detection of the machining current, and a differential voltage obtained by comparing this detection signal voltage with a reference value 27 controls the tension control drive motor (DC motor) 28 in analog.

Of course, the tension may be controlled by controlling the brake on the sending side of the wire electrode.

Although the above embodiments have been described with reference to examples such as a tension change control device, a wire elongation detection device, and a gap machining state detection/discrimination device, it goes without saying that other commonly used devices can be used.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an actual winding example of the present invention, FIG. 2 is a detailed view of a part thereof, FIG. 3 is a characteristic diagram of an experimental example for explaining the present invention, and FIG. 4 is a diagram of a winding example of the present invention. FIG. 2 is a partial configuration diagram of an embodiment of the present invention.

Claims (1)

[Scope of Claims] 1. In an apparatus in which a moving wire electrode applies electricity to a gap facing a workpiece with a small gap, the apparatus includes a tension control device for controlling the tension of the wire electrode, and a tension control device for controlling the elongation of the wire electrode. An electrical processing device using a wire electrode, characterized in that a detection device is provided, and a signal from the detection device controls the tension control device so that the elongation of the wire electrode is below a certain value. 2. A device for controlling the tension of the wire electrode, a device for detecting the elongation of the wire electrode, and a voltage in the processing gap, in a device that processes a moving wire electrode by applying current to a gap opposed to the workpiece with a minute gap, A device is provided to detect the energization state of the wire electrode using current or impedance as a signal, and the tension control device is controlled by the signals from both of the detection devices so that the elongation of the wire electrode is below a certain value. Electrical 7J equipment that uses wire electrodes.