JP2002239841A - Short circuit avoiding method in wire electric discharge machining - Google Patents

Abstract

PROBLEM TO BE SOLVED: To instantly avoid a short circuit state between electrodes by a simple process and improve machining efficiency in a short circuit avoiding method in wire electric discharge machining. SOLUTION: In response to occurrence of the short circuit state between a wire electrode 1 and a workpiece 2 in the wire electric discharge machining, a controller moves the wire electrode 1 backward along a machining slit and applies vibration to the wire electrode 1 to avoid the short circuit state. The controller periodically increases and decreases tension applied to the wire electrode 1 by a tension roller 10 of a wire electrode supply system 9 to generate vibration of the wire electrode 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for avoiding a short circuit at the time of wire electric discharge machining in which vibration is applied to a wire electrode in order to avoid a short circuit between a wire electrode and a workpiece.

[0002]

2. Description of the Related Art Conventionally, a wire electric discharge machine is shown in FIGS.
As shown in FIG. 3 and FIG. 3, a discharge machine is generated between the wire electrode 1 and the workpiece 2 to cut out the workpiece 2 such as cemented carbide or hardened steel. A processing tank 26 is provided on the provided work table 29. The lower wire head 6 attached to the lower arm 31 and the workpiece 2 attached to the work table 29 by a clamp or the like are installed in the processing tank 26. Also,
The upper arm 33 attached to the head 7 provided with the Z-axis driving device, the U-V-axis driving device and the like is provided with the upper wire head 5 facing the lower wire head 6. When starting the electric discharge machining, the wire electrode 1 is inserted in advance into the start hole 3 or the machining slit 4 drilled in the workpiece 2. When an inter-electrode voltage is applied between the wire electrode 1 and the workpiece 2, which are constantly supplied, and the workpiece 2 is discharged, the workpiece 2 is discharged into a predetermined machining shape by the discharge energy.
The wire electric discharge machining of the workpiece 2 is performed by the power supply device 30 of the NC device.
The workpiece 2 is formed with a continuous machining slit 4 in the workpiece 2 in accordance with the shape programmed in the controller of the NC device.

[0003] In the wire electric discharge machine, the wire electrode automatic feeder has been developed, the operator be performed even desorption of the workpiece, the work from the insertion of the wire electrode to the machining is completed, the As programmed into the controller It is automated so that it can be supplied in the process. When the processing of the workpiece 2 is completed and the processing of another workpiece 2 is started, and when the wire electrode 1 is disconnected during the electric discharge machining, the wire electrode 1
Is cut and removed, and the newly formed tip is inserted into the start hole 3 or the processing slit 4 of the workpiece 2 to set the wire electrode 1. As part of the automation of the electric discharge machining operation, the mounting operation of the wire electrode 1 from sending out the wire electrode 1 to cutting the wire electrode 1 and reinserting the wire electrode 1 into the machining slit 4 is automated.

In particular, FIG. 3 shows that a wire electrode 1 which has been annealed and straightened is provided with a start hole 3 previously formed in a workpiece 2 with or without the aid of a water flow.
Alternatively, an automatic wire feeder that passes through the processing slit 4 is shown. As shown in FIGS. 2 and 3, the automatic wire feeder supplies various kinds of direction changes to supply the wire electrode 1 fed from the source bobbin 11 attached to the source bobbin shaft 25 to the processing slit 4 or the start hole 3. Roller 12, brake pulley 1 for
3, a wire electrode supply system 9 including a tension roller 10, a guide roller 15 for changing the direction, a winding roller 22, and the like.

[0005] In the wire electrode supply system 9, a felt pad 16 is arranged on the upstream side of the brake pulley 13, and a felt brake 17 is provided to the brake pulley 13.
And a pulley opening / closing lever 18 are provided. Further, a tension roller 10 around which the wire electrode 1 is wound is provided downstream of the brake pulley 13. The tension roller 10 is driven by, for example, an electromagnetic brake,
Tension roller 1 by controlling the current to the electromagnetic brake
The rotation speed of 0 is controlled, and the tension of the wire electrode 1 is adjusted. Further, the wire electrode feed system 9
A disconnection detection sensor 14 is provided downstream of the tension roller 10 for detecting either the supply state or the disconnection state of the wire electrode 1.

[0006] From the source bobbin 11 to the wire electrode supply system 9
Is passed through the annealing roller 19 and the common roller 20, and a current is applied to the wire electrode 1 between the annealing roller 19 and the common roller 20 to anneal the wire electrode 1 and the habit of the wire electrode 1. taking to straighten. The wire electrode 1 that is straight droop,
The deformed portion at the tip is cut using a cutter, and the waste wire clamp is activated to be discarded to the waste wire hopper 24. The wire electrode 1 having a straightened tip is a common roller 2
From 0, it passes through a power supply or the like and is sent to the upper wire head 5 attached to the head 7, and then inserted into the start hole 3 or the processing slit 4 formed in the workpiece 2 disposed in the processing tank 26. The wire is guided by the winding roller 22 from the lower wire head 6 disposed in the processing tank 26 attached to the column 8 through the wire guide 21, a discharge roller for discharging the used wire electrode 1, a discharge pipe, and the like. The wire hopper 2 is pulled out from the wire guide 23 and discharged.
It is discharged to 7.

The wire electrode 1 is guided by the upper wire head 5 and the lower wire head 6, so that the wire electrode 1 is accurately positioned with respect to the workpiece 2 while restricting lateral runout between the two heads. To run. The lower wire head 6 is supported by the tip of a lower arm 31 attached to the head 7 so as to hang down from above the processing tank 26, and includes a direction changing roller and the like inside. In the downstream of the lower wire head 6, a pair of draw-out rollers, such as a pair of draw-out rollers, ie, take-up rollers 22, which draw out the wire electrode 1 through the guide pipe 32 and tension the wire electrode 1, are mounted outside the processing tank 26. ing. Wire electrode 1 annealed is straight extended been performed is inserted from its distal end to the start hole 3 or processing slits 4 of the workpiece 2. An example of this type of automatic wire feeder is disclosed in Japanese Patent Application Laid-Open No. 2-145215.

The workpiece 2 includes upper wire heads 5 facing each other.
It is fixed to the machining tank 26 in a state of being placed between the lower wire head 6, by suitable clamping means or supporting means and. The electric discharge machining of the workpiece 2 is performed in a state of being immersed in the machining fluid filled in the machining tank 26, or by preventing the occurrence of aerial discharge by supplying the machining fluid as a water flow to the electric discharge machining portion. It is. Processing tank 26
Is driven in accordance with the processing shape of the workpiece 2 in a plane defined by the X-axis and the Y-axis, for example, by a cross slide composed of an X-axis table and a Y-axis table. The Y-axis table is driven in the Y-axis direction by a Y-axis servo motor on the bed base, and the X-axis table with the processing tank is driven in the X-axis direction by the X-axis servo motor on the Y-axis table.

[0009]

[SUMMARY OF THE INVENTION Incidentally, in the wire electric discharge machine, when between the wire electrode and the workpiece is shorted during wire electrical discharge machining, or to increase or decrease the tension of the wire electrode in a short period, the wire electrode directly At present, vibration is generated in the wire electrode using a tapping mechanism or the like, thereby removing machining debris accumulated in the processing slit and eliminating a short circuit between the workpiece and the electrode. However, in the above-described method for eliminating the short-circuit state between the poles, since the avoidance processing is performed at the short-circuited point, when the workpiece is a thick member, the shape of the processing slit is in the traveling direction of the wire electrode. There was a bowing phenomenon, and in that case, it was found that even if the wire electrode was vibrated, it was not always effective in removing the machining debris. In addition, φ where wire electrodes are usually used
When a wire electrode having a diameter smaller than 0.2, for example, a diameter of about 0.1 or less is used, the width of the processing slit becomes small, and processing chips accumulate on the processing slit, resulting in a short circuit between the poles. Generate a state. Therefore, even in machining slit width less immediately eliminate swarf machining slit, it is necessary to a normal discharge is performed.

[0010]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems, and to immediately eliminate a short-circuit state caused by the accumulation of machining debris between a workpiece and a wire electrode. It is an object of the present invention to provide a method for avoiding a short circuit at the time of wire electric discharge machining, in which the gap is returned to a normal state, electric discharge machining is quickly restarted, and machining efficiency is improved.

According to the present invention, an upper wire head provided on a head and a column opposed to the upper wire head are formed on a column by a wire electrode fed from a source bobbin through a wire electrode supply system including a guide roller, a brake pulley, and a tension roller. The wire electrode is inserted into a start hole or a machining slit formed in the workpiece in order to perform a wire electrical discharge machining on a workpiece installed between the lower wire head and the workpiece. In a wire electric discharge machining method for performing wire electric discharge machining on the workpiece by electric discharge energy generated by applying a voltage between the electrodes, a controller causes a short circuit between the wire electrode and the workpiece during wire electric discharge machining. The wire electrode is moved along the machining slit in response to the occurrence of Performing control for avoiding the short-circuit state by applying vibration to the wire electrode while retracting relates shorting workarounds during wire electrical discharge machining according to claim.

The controller controls the tension applied to the wire electrode by the tension roller of the wire electrode supply system by periodically increasing or decreasing the tension to change the tension, thereby generating vibration of the wire electrode.

[0013] The change to periodically increase or decrease the tension applied to the wire electrode by the tension roller is achieved by increasing or decreasing the current to the electromagnetic brake that drives the tension roller.

The short circuit between the wire electrode and the workpiece is caused by the accumulation of machining chips generated during wire electric discharge machining on the machining slit, and the machining chips are caused by the vibration of the wire electrode and the machining. It is removed from the working slit by retreating along the slit.

The controller performs a control for ignoring an abnormal signal in wire electrode feed control such as a wire electrode disconnection signal or a wire electrode absence signal generated by the vibration of the wire electrode by the tension roller.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a method for avoiding a short circuit during wire electric discharge machining according to the present invention will be described below with reference to the drawings. This method of avoiding short circuits during wire electric discharge machining can be applied to, for example, the wire electric discharge machine shown in FIGS. 1, 2 and 3.

The illustrated wire electric discharge machine, the head 7 constituting the machine body, the upper wire head 5, processing tank 26
A lower wire head 6 disposed opposite to the upper wire head 5 is attached via a lower arm 31 hanging down. The upper wire head 5 is suspended from the head 7 and attached to the head 7 so as to be able to move up and down. Further, the upper wire head 5, about the vertical direction and the insertion hole is formed for inserting the wire electrode 1 through the die guide is attached to the tip portion. A wire guide for guiding the wire electrode 1 is provided at the tip of the die guide. Even if the tip opening of the wire guide is formed in a tapered shape like the conventional one,
Alternatively, it may be formed straight. Further, the workpiece 2 is formed with a start hole 3 or a processing slit 4 which is a processing path through which the wire electrode 1 is to be inserted. In addition, the insertion of the tip of the wire electrode 1 is performed with the head nozzle and the workpiece 2 as close as possible to each other.

In particular, this method for avoiding short circuits during wire electric discharge machining is characterized by the following processing steps in the above wire electric discharge machine. In the wire electric discharge machining method capable of achieving the short circuit avoiding method at the time of the wire electric discharge machining,
Is sent from a source bobbin 11 through a wire electrode supply system 9 including a guide roller 12, a brake pulley 13, and a tension roller 10. Then, the wire electrode 1, the wire head 5 on which is provided in the head 7, a workpiece 2 which is disposed between the lower wire head 6 opposite the upper wire head 5 provided on the column 8 wire electric discharge Automatically supplied for processing. First, the workpiece 2 is generated by inserting the wire electrode 1 into a start hole 3 or a processing slit 4 formed in the workpiece 2 and applying a voltage between the wire electrode 1 and the workpiece 2. Wire electric discharge machining is performed by the discharge energy.

The method of avoiding short circuit during wire electric discharge machining is as follows.
In particular, the controller provided in the NC power supply 30 causes the wire electrode 1 to retreat along the machining slit 4 in response to the occurrence of a short circuit between the wire electrode 1 and the workpiece 2 during wire electric discharge machining. It is characterized in that control for avoiding a short-circuit state by giving a vibration to the wire electrode 1 while performing. The controller periodically controls the tension applied to the wire electrode 1 by the tension roller 10 of the wire electrode supply system 9 to increase or decrease the tension to generate vibration of the wire electrode 1.

In this method for avoiding short circuit during wire electric discharge machining, the change for periodically increasing or decreasing the tension applied to the wire electrode 1 by the tension roller 10 is performed by the tension roller 1.
This is achieved by increasing or decreasing the current to a drive device such as an electromagnetic brake that drives 0. The short circuit between the wire electrode 1 and the workpiece 2 is caused by the accumulation of machining chips generated during wire electric discharge machining on the machining slit 4, and the machining chips are generated by the vibration of the wire electrode 1 and the machining slit 4. The wire electrode 1 is removed from the processing slit 4 by retreating along.

The controller is set so as to perform a control for ignoring an abnormal signal in the wire electrode feed control such as a wire electrode disconnection signal or a wire electrode absence signal generated by the vibration of the wire electrode 1 by the tension roller 10. Therefore, in the step of removing the processing waste from the processing slit 4, even if the disconnection signal of the wire electrode 1 is input to the controller from the wire electrode disconnection detector, that is, the wire electrode disconnection sensor 14, the signal from the wire electrode disconnection sensor 14 is used. no transition into the insertion process of the electrode 1. That is, when the wire electrode 1 is cut at the beginning of the operation of the wire electric discharge machine or during the wire electric discharge machining of the workpiece 2, the end of the wire electrode 1 is cut by a cutting mechanism (not shown). A new tip is formed on the electrode 1. The process of feeding the wire electrode 1 having a new tip portion of the wire electrode 1 to the upper wire head 5 by a feed roller from above is not performed.

[0022]

As described above, this method of avoiding a short circuit at the time of wire electric discharge machining performs control to avoid a short circuit state by vibrating the wire electrode while retracting the wire electrode along the machining slit. Only by controlling the electrode to retreat along the processing slit, a short circuit state can be avoided with a remarkably high probability as compared with the removal of processing chips from the processing slit, and the processing efficiency can be improved. Moreover,
Vibration can be applied to the wire electrode only by controlling the supply of current to the tension roller, and the tension of the wire electrode can be changed, and the vibration can be made very easily. Also,
The controller ignores abnormal signals in the wire electrode feed control such as the wire electrode disconnection signal and the wire electrode absence signal generated by the vibration of the wire electrode by the tension roller, so that the short-circuit condition can be eliminated immediately without fail. be able to.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a wire electric discharge machine capable of achieving a method of avoiding a short circuit during wire electric discharge machining according to the present invention.

FIG. 2 is a front view of the wire electric discharge machine shown in FIG.

FIG. 3 is an enlarged front view showing a wire electrode supply system in the wire electric discharge machine shown in FIG. 2;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Wire electrode 2 Workpiece 3 Start hole 4 Processing slit 5 Upper wire head 6 Lower wire head 7 Head 8 Column 9 Wire electrode supply system 10 Tension roller 11 Source bobbin 12, 15 Guide roller 13 Brake pulley 14 Disconnection detection sensor 16 Felt pad 17 Felt brake 18 Pulley opening / closing lever 19 Annealing roller 20 Common roller 21 Wire guiding part 22 Winding roller 23 Discharge wire guide 24 Waste wire hopper 25 Source bobbin shaft 26 Processing tank 27 Discharge wire hopper 28 Base 29 Work table 30 NC power supply 31 Lower arm 32 Guide pipe 33 Upper arm

Claims (5)

[Claims] An upper wire head provided on a head and a column provided opposite to the upper wire head by a wire electrode fed from a source bobbin through a wire electrode supply system comprising a guide roller, a brake pulley, and a tension roller. In order to perform wire electric discharge machining of a workpiece placed between the lower wire head and the lower wire head, the wire electrode is inserted into a start hole or a machining slit formed in the workpiece, and the wire electrode is inserted between the wire electrode and the workpiece. In the wire electric discharge machining method for performing wire electric discharge machining on the workpiece by discharge energy generated by applying a voltage between the electrodes, a controller causes a short circuit between the wire electrode and the workpiece during wire electrical discharge machining. The wire electrode is retracted along the machining slit in response to the A method for avoiding a short circuit at the time of wire electric discharge machining, wherein control is performed to avoid vibration by applying a vibration to the wire electrode. 2. The apparatus according to claim 1, wherein the controller periodically increases or decreases the tension applied to the wire electrode by the tension roller of the wire electrode supply system, and changes the tension to generate vibration of the wire electrode. The method for avoiding a short circuit during wire electric discharge machining according to claim 1. 3. The method according to claim 2, wherein the change to periodically increase or decrease the tension applied to the wire electrode by the tension roller is achieved by increasing or decreasing the current to an electromagnetic brake that drives the tension roller. short workaround during wire electrical discharge machining according. 4. A short circuit between the wire electrode and the workpiece is caused by accumulation of machining chips generated during wire electric discharge machining in the machining slit, and the machining chips are caused by vibrations of the wire electrode. The method according to claim 2 or 3, wherein the wire is removed from the machining slit by retreating along the machining slit. 5. The controller according to claim 1, wherein the controller ignores an abnormal signal in the wire electrode feed control such as a wire electrode disconnection signal or a wire electrode absence signal generated by the vibration of the wire electrode by the tension roller. The method for avoiding a short circuit during wire electric discharge machining according to any one of claims 1 to 4.