JPH07106500B2 - Wire cut electrical discharge machine - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a wire-cut electric discharge machine for electric discharge machining using fine wire electrodes.

[Prior art and problems]

Conventionally, it has been known to supply a machining current to a wire electrode in a wire-cut electric discharge machine by providing a conduction electron that contacts the wire electrode. However, the current-conducting current that has been conventionally used does not change in the middle if the contact pressure between the wire electrode and the current-conducting is set beforehand by a spring or the like. In this case, the current is worn on both the brush and the roller, and the contact state changes due to continuous use. Normally, the contact pressure is reduced due to the abrasion of the conduction electrons, and the conduction resistance is increased. If the electric discharge machining is continued under such a situation change, the machining current will gradually decrease and the machining efficiency will decrease, causing heat generation due to the contact resistance between the conduction electrode and the wire electrode, and generating a spark between them. There is a defect that causes a wire breakage. In particular, in recent years, a high-speed processing technology in which a large current is passed has been developed, and there is a problem that the consumption speed of the energizing pin is increased.

[Means for solving problems]

SUMMARY OF THE INVENTION In order to eliminate the conventional drawbacks, the present invention provides a current-carrying electron that supplies power for pulse discharge by contacting a traveling wire electrode and a current-carrying pressure contact with the wire electrode. A controllable pressurizing device, a detecting device for detecting a contact state between a wire electrode and a conduction electron, a comparing circuit for comparing a detection signal of this detecting device and a comparison reference value indicating an appropriate pressurizing range, and this comparing circuit. And a control circuit for controlling the pressing force of the pressurizing device according to the output of the.

[Action]

The contact state between the wire electrode and the conduction electrode is detected, the detected value is compared with the comparison reference value that is set appropriately by the comparison circuit, and the conduction circuit is contacted with the wiring electrode by the control circuit based on the output of this comparison circuit. The pressure of the pressurizing device is controlled. Therefore, the contact energization state between the wire electrode and the conduction electrons is optimally controlled.

〔Example〕

The present invention will be described below with reference to an embodiment of the drawings. 1 is the wire diameter
A thin wire electrode of about 0.03 to 0.5 mmφ, which is usually supplied from a winding reel and travels with a predetermined tension and speed by the action of a take-up device and a brake (not shown).
The workpiece is opposed to the moving wire electrode 1 for electrical discharge machining. Reference numeral 2 is a stator of a conduction member that applies a machining current to the wire electrode 1, 3 is a conduction member that applies pressure from the opposite side, 4 is a pressure guide of an insulator, and 5 is a pressure lever. Pressurize. Reference numeral 7 denotes an electromagnet iron core, which exerts a magnetic attraction force on the support piece of the lever 5 by excitation of the coil 8 to perform pressurization control. Reference numeral 9 denotes a spring that repels a magnetic attraction force, and an electromagnetic force is applied to the lever 5, the guide 4, and the current carrying member 3 against the spring. The fixed-side communication 2 is attached to the fixed wall surface 10, and the piezo element 11 is sandwiched between them to detect a pressure-electric signal. Reference numeral 12 is a signal detection circuit from the piezo element 11, 13 is a signal comparison circuit, and the comparison reference value is appropriately set by the setting device 14. The reference value is set to an optimum value depending on the material of the wire electrode 1, the wire diameter, the processing pulse conditions, etc., but can be set manually or by NC program control. Reference numeral 15 denotes an excitation control power supply for supplying an excitation current to the coil 8, which controls the excitation by the output signal of the comparison circuit 13. Reference numeral 16 is a lead wire for connecting the machining power source to the electronic device 2.

In the above, the wire electrode 1 is sandwiched between the conducting electrons 2 and 3, and the initial setting of the pressing force is magnetic attraction by the excitation of the magnet coil 8 to pressurize the lever 5, and the pressure guide 4 to the conducting electron 3. The pressure is applied to maintain the contact energization state with the wire electrode 1 at an optimum value.
The detection signal of the piezo element 11 in this state is in the proper pressurization range, and the signal of the detection circuit 12 for detecting this is compared with the comparison circuit.
When comparing in addition to 13, the control power supply 15 controlled by the comparison output maintains the initial state. In the meantime, by continuing the machining, the current carrying electrodes 2 and 3 that pressurize and slide by the wire electrode 1 moving and moving will be worn and deformed.
Since the magnet attracts the lever 5 by a constant exciting current and exerts pressure against the spring force 9,
When 3 wears, the pressure contact force decreases
The detection signal of 1 is reduced. As a result, the output signal compared with the reference value of the comparison circuit 13 increases, and the control coil 15 controls the exciting coil 8 to strongly excite it. As a result, when the pressing force of the conduction electron 3 increases, the detection signal of the piezo element 11 increases and the signal applied from the detection circuit 12 to the comparison circuit 13 increases, so the comparison output of the comparison circuit 13 decreases and the control power supply 15 increases.
Control to keep the excitation of the coil 8 by
As a result, the pressure contact force with the wire electrode 1 is maintained constant even when the conduction electrons 2 and 3 are worn, so that the contact energization state between the two is always controlled to be constant. For this reason, it is possible to completely prevent the current flow rate from decreasing the machining efficiency as in the past, and to completely prevent the occurrence of wire electrode disconnection accidents due to heat generation and sparks due to defective contact, and a stable and highly efficient wire cut discharge. Processing can be performed.

It should be noted that the comparison of the detection signal with the reference value is not limited to analog comparison, but digital determination can be performed, the reference value is set in several stages, the determination output is performed, and the control power supply 15 is digitally changed stepwise. It can also be controlled. Further, the detection of the contact state between the conduction electron and the wire electrode may be carried out by detecting the change of the energization resistance and the energization current between them, and various corresponding detecting devices can be used. Further, as a pressurizing device for pressurizing and controlling the conduction electrons, thermal expansion, magnetostriction, electrostriction, other electrical or mechanical activator, liquid or gas activator can be arbitrarily used.

Further, although the conducting electrons of the embodiment are provided so as to face each other with the wire electrode 1 sandwiched therebetween, one may be a pressure pad or a hard insulator such as ceramic. In general, the conduction is provided so as to energize the wire electrodes on the upper and lower sides of the work piece, but in that case as well, stable energization is achieved by detecting the contact state and controlling the pressurization to maintain a constant energized state. Can be done. The same applies when a roller is used for communication.

〔The invention's effect〕

INDUSTRIAL APPLICABILITY As described above, the present invention is provided with a pressurizing device capable of controlling the pressure applied to the conduction electrons and a contact detection device for detecting the contact state between the wire electrode and the conduction electrons, and further based on the detection signal of the contact detection device. Since the control circuit for controlling the pressurizing device is provided so as to optimize the contact state between the wire electrode and the conduction electrode, even if the conduction electron is worn, the control of the pressurizing device can be used to control the contact with the wire electrode. The contact pressure is optimally controlled to keep the contact energization state stable and the energizing current is not lowered, and the crest value, pulse width, waveform, etc. of the machining pulse are constantly controlled to be constant and stable high speed, Highly efficient electric discharge machining can be performed. Further, it is possible to completely prevent the occurrence of the electrode disconnection accident due to the heat generation and the spark due to the defective contact between the wire electrode and the conduction electron, and the stable electric discharge machining can be performed. Further, based on the machining program input to the NC device, it is strong during rough machining and weak during finishing, and the contact pressure is optimally controlled to reduce wear of the conduction and extend the replacement period.

[Brief description of drawings]

 The drawing is a block diagram of an embodiment of the present invention. 1 ... Wire electrode 2, 3 ... Conductor 4 ... Pressurizing guide 5 ... Pressurizing lever 6 ... Pressurizing ball 7 ... Magnetic core 8 ... Exciting coil 9 ... Spring 11 ... Piezo element 12 ...... Signal detection circuit 13 …… Comparison circuit

Claims (1)

[Claims] 1. An apparatus for machining a wire electrode, wherein a machining fluid is supplied to a gap facing a workpiece while the wire electrode is run and moved between guides at a predetermined tension and speed, and a pulse discharge is repeated by energizing the machining fluid. A current-carrying electron that contacts the traveling wire electrode to supply the electric power of the pulse discharge, and a pressure device that press-contacts the current-carrying electron with the wire electrode.
A detection device that detects a contact state between the wire electrode and the conduction, a comparison circuit that compares a detection signal of the detection device and a comparison reference value that is set based on an appropriate pressure range of the pressure contact, A wire-cut electric discharge machine comprising: a control circuit for controlling the pressure applied by the pressurizing device according to the output of the comparison circuit.