JPS6146251B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention uses a thin wire, moves between guides while applying a predetermined tension, faces the workpiece using the wire as an electrode, and processes a wire cut by passing current through the opposing gap. Regarding the improvement of

The thin wire used is a thin wire having a wire diameter of about 0.05 to 0.5 mmφ. In order to improve machining accuracy, it is desirable to apply high tension to the wire electrode in the machining section to keep it in a straight line, but if the tension is too strong, the wire will break at the slightest thing, and the wire will break. It becomes easier to do. Therefore, it was not possible to apply a tension exceeding a predetermined value, and therefore it was not possible to improve the machining accuracy.

In view of this point, the present invention is proposed for the purpose of improving processing accuracy by imparting substantially higher tension to the wire electrode than before, and the present invention is proposed by applying a pulse to the wire electrode at a frequency of at least 100 Hz or more. By applying a tension that varies over time, the wire unwound from the winding frame is given elongation, thereby improving the straightness of the wire as it moves between guides.

The pulsed tension is applied as follows. That is, the thin wire is moved between the guides under a predetermined tension by the interaction of a brake and a drive device, and a brake or drive device is provided in which the torque of the brake or the torque of the drive device is controlled in a pulse manner. , thereby controlling the tension applied to the wire in a pulse manner.

The present invention will be explained below with reference to an embodiment of the drawings.
In Fig. 1, 1 is a thin wire with a wire diameter of about 0.05 to 0.5 mmφ, which is moved between guides 2, used as an electrode to face the workpiece 3, and supplies machining fluid (usually water). Processing is carried out by applying electricity. The machining liquid supply nozzle and the current supply source are omitted and not shown. Reference numeral 4 denotes a winding frame around which the wire 1 for processing is wound, and the wire is sequentially fed while being unwound. The supplied wire passes through the processing portion between the guides 2 while being guided by the guide rollers 6, and the exhausted wire after processing is moved by the guide rollers 6 and wound onto the winding frame 5. 7 is a brake provided in front of the processing section when the wire 1 moves in the direction of the arrow, and 8 is a drive device that applies a driving force for movement to the wire that has passed through the processing section and comes out. A required tension is applied to the wire 1 between the guides 2 by the tensile force and the brake 7 to cause the wire 1 to move.

The brake 7 is reversely rotated by a pressure roller 71 and a torque motor 73. brake roller 72
The brake is applied by sandwiching the wire 1 between the rollers 71 and 72 and keeping the rollers 71 and 72 in pressure contact. Reference numeral 74 denotes a clutch that connects and disconnects the connection between the motor 73 and the roller 72, and is configured to pulse-control this clutch to change the brake torque in a pulse-like manner. Further, the drive device 8 also includes the pressure roller 8.
1 and a drive roller 82 rotated forward by a motor 83.
The wire 1 is sandwiched between the two and the drive torque is applied.

FIG. 2 shows an oscillator 9 that supplies control pulses to the clutch 74, and supplies pulses obtained by half-wave rectification of the output of the oscillation transformer to the clutch 74 coil. The oscillation frequency used is approximately 0.1 to 10 KHz.

Due to the action of the brake 7 and the drive device 8, the wire 1
The brake 7 is moved in the direction of the arrow with tension acting on it, and the clutch 75 of the brake 7 is controlled on/off by the output of the oscillator 9 to connect and disconnect between the drive motor 73 and the brake roller 72. Since the brake torque is changed in a pulse manner, the tension acting on the wire 1 is therefore applied in a pulse manner. The frequency of this pulse change must be at least 100Hz or higher to be effective. A continuous driving torque is applied to the wire 1 by the driving device 8, but as the brake 7 changes the torque in a pulsed manner as described above, the wire 1 between the two is instantaneously applied to the driving device in a pulsed manner. A force greater than the driving torque by 8, that is, a tension force is applied, and the result is substantially the same as that of an extremely large tension force, and the wire 1 is sufficiently stretched and its linearity is significantly improved. Even if the tension acting on the wire 1 acts as described above, it does not act continuously but acts instantaneously in the form of a pulse, so that the drive can be controlled without disconnection. In this way, the tension is applied in a pulsed manner, and by substantially increasing the tension and moving the wire 1, the linearity of the wire 1 is improved, and the wire between the guides 2 is in a straight line under tension, facing the workpiece 3. Therefore, the processing accuracy using this wire is significantly improved.

For example, using a 0.2 mmφ Cu wire, it was moved between guides under a constant tension of 750 g using the conventional method, and was used as an electrode to cut a 50 mmφ circular cut into an S55C plate. When the machining fluid was water with a resistance value of 2 × 10 ₄ Ωcm, after 5 machinings,
As for machining accuracy, the maximum diameter error in circular machining is 18
They were μ, 19μ, 16μ, 15μ, and 16μ. Next, according to the present invention, a magnetic clutch brake is used as the brake, and this brake torque is controlled in a pulse manner to apply a high load that exceeds the tensile strength of the wire electrode material, to the extent that the wire does not break even when constantly applied for 1.2 mmsec. By applying low loads alternately,
When controlling the tension so that a load of 2 kg is applied to the wire by changing the tension in a pulsed manner, the maximum error in the diameter of the circular machined hole after 5 machining operations under the same machining conditions as above was 6 μ, 8 μ, 4 μ, respectively. 6μ, 3μ
The machining accuracy has been significantly improved compared to the conventional method. In addition, an electrostatic clutch brake was used for the brake, and a high load exceeding the tensile strength of the wire electrode material was applied by applying the brake for 0.8 msec.
When the maximum load on the wire is set to 1.4 kg by alternating pulse control with a low load that does not break even if sec is constantly applied, the maximum errors in the five processing steps are 4 μ, 6 μ, 8 μ, respectively. 2
It was μ, 3μ. In both cases, high-precision machining was possible through pulse-like control of brake torque.

The above description has been given of controlling the brake torque in a pulsed manner, but in order to control the tension of the wire in a pulsed manner, the driving device 8 may be provided with a device that applies the driving torque in a pulsed manner. For this purpose, a clutch may be provided on the drive shaft connecting the drive roller 82 and the motor 83, and the clutch may be controlled by a pulse oscillator. Alternatively, both the drive device 8 and the brake 7 may be capable of controlling torque in a pulse manner, and both may be controlled synchronously or out of phase.

As a modification, it is possible to use a drive pulley for the winding frame that rotates in a pulsed manner as shown in FIG. 10 is a disc with an outer groove formed on its outer periphery; 1
Reference numeral 1 denotes a rotary motor, and 12 a pawl that is caught in the groove.The pawl 12 is moved up and down by the excitation of a magnet 13, and the hook is released. Rotating force is always applied to the disk 10 by the motor 11, but there are claws 1 in the outer circumferential groove.
Since 2 is stuck, it cannot rotate freely. Then, when the magnet 13 is excited by the output pulse of the oscillator, the claw 12 is attracted, the hook is released, and the disk 10 rotates to the next groove. By controlling the pawl 12 in a pulsed manner, the step rotation of the disc 10 is repeated, and the wire is wound in a pulsed manner.As a result, the wire 1 moving between the guides 2 is wound in a pulsed manner. A pulse-like tension will work.

A few examples of the method of applying pulsed tension to the wire have been described above, but various other modifications are possible. In any case, by applying pulsed tension, a substantially strong tension can be applied to the wire, which improves the straightness of the wire and significantly improves the processing accuracy of wire cuts. Also, of course, by improving the straightness of the wire, arcs, short circuits, etc. are less likely to occur, and stable machining can be continued and machining speed can be increased.

[Brief explanation of the drawing]

FIG. 1 shows an embodiment of the present invention, FIG. 2 shows an embodiment of an oscillator, and FIG. 3 shows an embodiment of a reel drive pulley. 1 is a wire, 2 is a guide, 3 is a workpiece,
4 and 5 are winding frames, 6 is a guide roller, 7 is a brake, and 8 is a drive device.

Claims (1)

[Claims] 1. In wire cutting, in which a thin wire is moved between processing section guides while applying a predetermined tension, the wire is used as an electrode to face the workpiece, and electricity is applied to the opposing gap for processing, the wire between the processing section guides is Machining while applying tension that changes in pulses at a frequency of at least 100 Hz by alternately applying a high load that exceeds the tensile strength of the electrode material and a low load that does not break even if constantly applied to the electrode. A current-carrying wire cutting method characterized by: