JPS6263018A - Wire electrode breaking position detecting method in wire-cut electric discharge machine - Google Patents

Abstract

PURPOSE:To aim at smooth separation of an electrode from a groove or a concave part in a workpiece, by pulling the wire electrode in leaving an upper wire guide held at a machining position intact and, after the wire electrode comes off the workpiece, separating the upper wire guide from that position and detecting a tip of the electrode between the upper wire guide and a workpiece table. CONSTITUTION:When retraction of a wire electrode W progresses and contact with a groove in a workpiece P is released free, output from a comparator 145 is outputted to a numerical control device 42, and in response to this movement, the N/C device 42 separates a wire guide 12 from a workpiece table 10 toward an upper part, while a wire handling unit 90 being so far retracted during electric discharge machining is made to move up to a position where the wire electrode W is interposed between cutters of a cutting device as well as between contact makers of a wire detecting device. When retraction of the electrode W progresses and it comes off the wire detecting device, output of a detecting circuit 140 is outputted to the N/C device 42 so that hoisting motion of the wire electrode is suspended. With this constitution, even at the time of disconnection during taper machining, the wire electrode is smoothly pulled out, thus its breaking position is detectable without fail.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to wire-cut electrical discharge machining, and more particularly to a wire electrode breakage position detection method for automatically detecting the breakage position of a sharpening wire electrode where the wire electrode is broken during electrical discharge machining. .

2. Description of the Related Art Conventionally, an upper wire guide and a lower wire guide are provided above and below a work table that holds a workpiece, respectively, and a wire feed mechanism is provided that clamps a wire electrode and sends it out downward. An electric discharge machining device is used for the wire cutter 1 in which a recovery device is installed. In such an electrical discharge machining apparatus, when changing the electrical discharge machining position of a workpiece, it is necessary to cut the wire electrode once and then automatically tension the wire electrode anew between the upper wire guide and the lower wire guide. In addition, if the wire electrode breaks in the electrical discharge machining area, after pulling the broken end of the wire electrode upward from the electrical discharge machining area, contact and separate the part that is bent or has a rough surface, and then move the wire electrode to the upper wire guide. Automatic tensioning between the wire guide and the lower wire guide is required.

For this reason, the applicant has already proposed an automatic wire connection device in which a wire cutting device and a wire breakage position detection device are provided below the upper wire guide.

If the wire electrode breaks for some reason during electrical discharge machining and the wire breakage position is to be detected by the above-mentioned automatic wire connection device, the upper wire guide is raised from the processing position, and the wire breakage position detection device of the automatic wire connection device is moved to the upper wire guide position. When the wire electrode is held between the contacts of the wire breakage position detection device and a current is passed between the contacts, the wire electrode is wound up, and the current flow between the contacts stops, that is,
The wire breakage position is detected when the wire electrode passes between the solid contacts and the solid contacts are insulated, but during taber machining, the wire electrode is perpendicular to the top surface of the workpiece. In other words, the length of the machined groove is from 11WI to FA.
As a result, one side of the circumferential surface of the wire electrode is pressed against the opposing inner surface of the machined groove, and the wire electrode, which has a tendency to bend or has a rough surface due to wire breakage, gets caught in the machined groove and is pulled smoothly. A problem arises in which it cannot be raised.

Problems to be Solved by the Invention It is an object of the present invention to provide a wire electrode breakage position detection method that can smoothly pull up the wire electrode from the groove being processed in the workpiece even if a wire breakage occurs during taber machining. The purpose is

Means and operation for solving the problems The present invention provides a method of applying a constant voltage between the wire electrode and the workpiece and pulling up the wire electrode while detecting a short circuit between the workpiece and the wire electrode when the wire electrode is disconnected during electrical discharge machining. After the short circuit is no longer detected, the upper wire guide is raised to a predetermined position, the wire detection means is moved to the upper wire guide position, the wire electrode is held between the contacts of the wire detection means, and a voltage is applied between the contacts. is applied, and the wire electrode is pulled up while detecting that the contacts are short-circuited by the wire electrode, and the wire electrode is Detects the position of wire breakage.

Example Hereinafter, the present invention will be described in detail with reference to the drawings.

1 to 3 show a wire cut electric discharge machine to which a wire breakage position detection method according to an embodiment of the present invention is applied. During the wire cut electric discharge machining, a work table 10 for holding a work P is used. We are prepared. The work table 10 is provided movably in the directions of horizontal orthogonal axes X and Y with respect to a base frame (not shown). An upper wire guide 12 having a wire passage 13 is provided above the work table 10, and a lower wire guide 14 having a wire passage 15 is provided below the work table 10. The lower wire guide 14 is fixed to a base frame that supports the work table 10, and the upper wire guide 12 is provided so as to be movable in the X and Y axes directions and movably in two vertical axes directions with respect to the base frame. The upper wire guide 12 is attached to the support frame 11, and when performing tapering processing, the upper wire guide 12 is adjusted in position horizontally with respect to the lower wire guide 14 so that the wire electrode W is stretched diagonally at a predetermined angle.

The wire-cut electrical discharge machining apparatus includes a wire feeding mechanism 23 that feeds the wire electrode W downward from above the upper wire guide 12 during electrical discharge machining. The wire V feeding mechanism 23 includes a wire reel 24 driven by a motor 25 and a pair of wire guide rollers 26 that sandwich the wire electrode W fed out from the wire reel 24 above the upper wire guide 12.
．． 26, a pair of wire feed rows 527, 27 which are disposed below one side of the lower wire guide 14 and sandwich the wire electrode W that has passed through the wire passage 15 and feed it downward, and a motor that rotationally drives both rollers 27 and 27. It is equipped with 28. A wire collection device 29 for collecting the wire electrode W is provided below the lower wire guide 14, and the device 29 has a belt conveying device 30 for sandwiching the wire electrode W between belts and feeding it into a collection box 31. We are prepared. During M-heavy machining, the Wi-V electrode W is wire feed roller 27°27
The wire is continuously sent out downward by the wire guide 12, passes through the machined hole or groove of the workpiece P, and then passes through the wire passage 15 of the lower wire guide 14 to the wire recovery device 29. Belt conveyance 8
Incorporated into @30. On the other hand, if the wire electrode W is disconnected due to abnormal discharge or the like during electrical discharge machining, the disconnected end of the wire electrode W is moved above the workpiece P by the reverse rotation drive of the motor 25 and the drive of the wire feed rollers 22, 22 by the motor 21. be pulled up. Note that the rollers 22 and 22 are driven by a solenoid-type driving means (not shown) to connect the wire electrode W.
The electrode holding position shown in FIG. 1 is taken only when pulling down the wire electrode W during automatic wire connection and when pulling up the wire electrode W when the wire electrode W is disconnected. moreover,
A power supply contact 32 is provided above the upper wire guide 12, and one end of the discharge circuit 33 is connected to a wire electrode W via a changeover switch 41 and a power supply contact 32, which will be described later.
The other end of the discharge circuit 33 is connected to a grounded workpiece P.

The upper wire guide 12 and the lower wire guide 14 are each connected with a jet liquid supply pipe 34.35 for supplying a jet liquid as a machining liquid into the wire passage 13.15. During electrical discharge machining, injection liquid is supplied to the wire passage 13 of the upper wire guide 12 and the wire passage 15 of the lower wire guide 14, respectively. The injection liquid supplied to the wire passage 13.15 is emitted towards the workpiece P and cools the wire electric wire l4iW. The work P is machined by stable underwater discharge generated between the work P and the wire electrode W.

Next, the automatic wiring device will be described. This device is constructed in substantially the same manner as that disclosed in the patent application “Wire-cut electric discharge application II automatic wire connection device” previously filed by the present applicant, and includes a housing 50 fixed to a support frame 11. A pneumatic motor 60 and a pneumatic cylinder 70 are attached to the housing 50. Further, a wire processing unit 90 is fixed to a movable shaft 100 which is provided to be able to rotate integrally with a rotating shaft (not shown) of a motor 60 and to be movable in the relative axial direction, and the unit 90 is rotated by the motor 60. The unit 90 is also moved in the height direction by the cylinder 70 via a support plate that rotatably supports the unit 90. As shown in FIGS. 2 and 3, a pneumatic wire cutting device 110 consisting of a pair of cutter blades 111 and 112 is installed at the outer end of the wire processing unit 90, and a wire electrode W is introduced at the time of expansion. A pair of nozzle portions 121.1 which define a nozzle hole 125 (FIG. 1) when closed.
Pneumatically driven nozzle hole forming sections 120 consisting of 22 are provided in sequence in the rotating direction of the unit 90, and a wire detection device 130 is provided in alignment with the cutting device @110 in the height direction.

This wire detection device 130 has a fixed contact 131,
It includes a movable contact 132 that is driven forward and backward, and a solid contact 13
1,132 is a wire electrode detection circuit 140 shown in FIG.
The output V of a detector 144 that is connected to both terminals 142 and 143 of the AC power supply circuit 141 and detects the potential difference between the two terminals.
t is compared with the reference potential VC by the comparator 145, and when the wire electrode W is not interposed between the contacts 131 and 132 and a non-conducting state occurs, a potential difference exceeding the reference potential VC occurs, and a signal from the comparator 145 is sent to the NG device. ! The signal is output to the disconnection position detection input terminal 42.

Furthermore, in order to detect a short-circuit state between the workpiece P and the wire electrode W when the wire electrode is disconnected, the wire electrode detection circuit 1
NG to one terminal 143 of AC power supply circuit 141 of 40
In accordance with a wire electrode disconnection position detection command from the device W42, the wire electrode W is connected via the changeover switch 41 that switches to the switching position shown in FIG. 1 and the above-mentioned power supply contactor 32.

Hereinafter, a method for detecting a disconnection position when a wire electrode is disconnected in the wire-cut electrical discharge machine configured as described above will be described.

If the wire electrode W is disconnected due to some abnormality during electric discharge machining, the electric discharge machining is stopped by the operation of a disconnection detector (not shown). Next, the NC device 42 outputs a wire breakage position detection command, switches the changeover switch 41 to the state shown in FIG. The wire reel 24 is rotated by the motor 21, and the wire reel 24 is rotated by the motor 25, so that the wire electrode W is pulled up from the machining groove of the workpiece P.

At this time, the wire passage 13 of the upper wire guide 12 is disconnected during taper machining, and even when the wire electrode W is pulled up inside the workpiece P in an oblique direction, the wire passage 13 of the upper wire guide 12 remains in the extension line of the machining groove.
Since the wire electrode W is pulled up along the axis of the machined groove, even if the wire electrode W has a tendency to bend or has a rough surface at the broken end, it can be pulled up smoothly without being caught in the machined groove. On the other hand, by switching the changeover switch 41, power is supplied to the wire electrode W from the wire detection circuit 140, and if the tip of the wire electrode W is in the machining groove of the workpiece P, the electrode W and the workpiece P are connected, and eventually both ends Since the terminals 142 and 143 are shorted, there is no output from the detector i'lG 140. On the other hand, when the wire electrode W separates from the groove of the workpiece P as the pulling progresses and the contact between the wire electrode W and the workpiece P is broken, both terminals 142 and 143 immediately become non-conductive, corresponding to the potential difference between them. The output Vt of the detector 144 is the reference potential V
C, the output from the comparator 145 is output to the disconnection position detection input terminal of the NC device 42.

The NC device 42 drives the Z-axis in response to the output to separate the upper wire guide 12 upward from the work table 10, and also drives the motor 60 and cylinder 70 to process the wire that has been evacuated during electrical discharge machining. The unit 90 is first moved to a position where the wire electrode W is interposed between the cutter blades 111 and 112 of the wire cutting device 110 and the contacts 131 and 132 of the wire detection device 130, and then the wire feed rollers 22, 22, etc. Wind up the wire electrode W.

During this winding, the wire detection device 130 detects the contacts 131,
The fixed contacts 131' and 132 are connected to terminals 142 and 143 of a wire detection circuit 140 that operates as described above. Therefore, the wire electrode W is pulled up and the contact 131.
132, the detection circuit 140 has terminals 142.
143 immediately becomes non-conducting, and circuit 140 becomes nonconductive as described above.
The output is output to the NC device 42. In response to this output, the NC device 42 stops the winding operation of the wire electrode W. Therefore, the cutting position of the wire electrode is determined by the wire detection device 1.
It will stop at position 30, which means that the cutting position of the wire electrode has been detected. As in the past, the wire electrode W is pulled down appropriately (depending on the thickness of the workpiece P), the portion where the surface has been roughened due to electrical discharge machining is cut by the wire cutting device 110, and then the automatic wire connection operation is performed. urge

Effects of the Invention As described above, according to the present invention, the wire electrode is pulled up while the upper wire guide is held at a processing position close to the workpiece, and after the wire electrode is removed from the hole or groove of the workpiece, the upper wire guide is moved to the workpiece. Since the tip of the wire electrode is separated from the table and detected between the upper wire guide and the work table, it can be pulled up smoothly from the hole or groove of the wire electrode even in the event of a wire breakage in the Taber hO■. Even if a recess is formed in the workpiece, the wire electrode disconnection position will not remain in the workpiece.
It is possible to reliably detect the disconnection position of the wire electrode.

[Brief explanation of drawings]

FIG. 1 is an overall configuration diagram showing a wire-cut electrical discharge machine for carrying out a wire electrode breakage position detection method according to an embodiment of the present invention, and FIG. 2 is a plan view of the wire processing unit shown in FIG. FIG. 3 is a partially cutaway side view of the unit. DESCRIPTION OF SYMBOLS 10... Work table, 12... Upper wire guide, 22... Wire feed roller, 23... Wire feed device, 29... Wire collection device, 130... Wire detection device, 140...・Wire detection circuit.

Claims (1)

[Claims] When the wire electrode breaks during electrical discharge machining, a constant voltage is applied between the wire electrode and the workpiece, the wire electrode is pulled up while detecting a short circuit between the workpiece and the wire electrode, and after the short circuit is no longer detected, the upper wire guide is moved to a specified position. position, the wire detection means is moved to the upper wire guide position, the wire electrode is held between the contacts of the wire detection means, and a voltage is applied between the contacts so that the wire electrodes short-circuit the contacts. A wire electrode in a wire-cut electrical discharge machine that detects a wire electrode breakage position by pulling up the wire electrode while detecting that the wire electrode is broken, and detecting that conduction between the contacts is lost when the wire electrode passes through the breakage part. Disconnection position detection method.