JPH0657371B2 - Wire cut electrical discharge machining method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a wire-cut electric discharge machining method, and more particularly to a wire-cut electric discharge machining method performed under a state where a wire electrode is tilted, for example. Based on the detection of the short circuit of the wire electrode that occurs immediately before the release of the wire electrode, by forcibly excluding the free micromachining piece, it relates to the wire cut electric discharge machining method that prevents the disconnection due to the occurrence of the short circuit of the wire electrode. is there.

(Prior Art and Problems) The applicant of the present application uses a manufacturing apparatus such as that shown in FIG. 2 which is configured by combining a wire cut electric discharge machine and a milling machine, for example. Proposed first "extrusion die and its manufacturing method", in which all the parts are automatically processed to significantly reduce the manufacturing man-hours and reduce the manufacturing cost. 58-182319). In FIG. 2, reference numeral 1 is a workpiece, 2 is a working table, 3 and 4 are control motors for driving the working table in the orthogonal X and Y directions, 5 is a wire electrode, and 6 is a wire. Electrode supply rollers, 7 and 10 tension rollers, 8 upper guides, 9 lower guides, 1
Reference numeral 1 is a scraper roller, 12 and 13 are control motors for moving the upper guide 8 in the orthogonal X and Y directions, 14 is a milling head, 15 is a milling cutter, and 16 is a control motor. Above milling cutter
It shows that the feed of the milling cutter 15 in the head 14 is controlled.

However, by using the manufacturing method proposed above, for example, as shown in FIG. 3, an extrusion die having a bearing hole 17 having a radiused portion (arrows A, B and C shown in the drawing) having a relatively small radius of curvature, or As shown in FIG. 4, when processing a back relief portion of an extrusion die having a bearing hole 18 in which a mohair portion 19 exists, a small piece (a loose portion in the present invention, referred to as the present invention) of a part of a workpiece is formed on the back side of the extrusion die. An undesired phenomenon occurs in which minute work pieces are released. The phenomenon of generation of the loose micro-machined pieces will be described with reference to FIG.

In the processing step for forming the back relief portion 20 of the extrusion die, as shown in FIG. 5 (A), the wire electrode 5 corresponds to the inclination angle of the back relief inclined surface 20 ′ forming the back relief portion 20. Under the condition that it is tilted at the tilt angle θ,
It moves so as to pass through the depth position P ₁ of the bearing length 1 at each desired position of the bearing hole 21. Then, depending on the value of the inclination angle θ of the wire electrode 5, the passing locus of the wire electrode 5 may intersect at a point O as shown in the figure. FIG. 5 (B) is a diagram showing the locus of the cutting work by the wire electrode 5 in order to make the state of the cutting work in the working process of the back relief portion 20 easy to understand. Upper surface 1-1 and lower surface 1-2
In the case where it exists between and, the free micromachining piece 22 is generated on the lower surface 1-2 side as shown in the drawing. Reference numeral 23 in the figure represents the locus of the point P ₁ . The arrow a in the figure indicates an intersection P ₂ between the upper surface 1-1 of the workpiece 1 and the wire electrode 5.
, The arrow b indicates the direction of movement of the locus of the intersection P ₃ between the lower surface 1-2 of the workpiece 1 and the wire electrode 5.

The free micromachining piece described above is, for example, as described above, the rounded portions A, B, C in the back relief processing step of the extrusion die having the bearing holes 17 having the rounded portions A, B, C as shown in FIG. Bearing hole 1 having mohair portions 19 as shown in FIG.
It occurs at a position corresponding to the mohair portion 19 in the back escape portion processing step of the extrusion die having No. Then, the problem occurs in a state immediately before the loose microfabricated piece is loosened. That is, for example, in the mode shown in FIG. 5 (B), the wire electrode 5 at the start of processing (shown in FIG. 5 (A))
Is on the straight line connecting the points P ₁ , P ₂ and P ₃ , the cutting point on the lower surface 1-2 moves from the point P _{3 in the} direction of the arrow b in the figure as the machining progresses. When the cutting point approaches the point P ₃ , the free micromachining piece 22 acts in the direction of sandwiching the wire electrode 5, so that a short circuit phenomenon occurs between the wire electrode 5 and the workpiece. Therefore, there is a problem that not only the processing is stopped but also an undesired processing failure such as disconnection of the wire electrode 5 occurs due to the short circuit phenomenon.

(Means for Solving Problems) The present invention is intended to solve the above problems, and therefore the wire-cut electric discharge machining method of the present invention uses wire electrodes to detect movement information of a machining table. In the wire-cut electric discharge machining method, in which the wire electrode is tilted with respect to the workpiece placed on the machining table to perform cutting with a tapered surface of a predetermined shape, a short circuit is generated. In addition to providing a short-circuit detecting means for detecting, a jet nozzle for ejecting liquid as a jet flow is provided, and it is detected that a short circuit has occurred between the wire electrode and the workpiece and that the short circuit has been maintained for a predetermined time. On the condition that the above was done, at this time, the jet stream was jetted by the jet nozzle in a cutting gap manner to cause the short circuit. The feature is that pressure is applied to the micro-machined piece that is being inserted so that the small machined piece is released from the workpiece and eliminated. Hereinafter, description will be given with reference to the drawings.

(Embodiment of the Invention) FIGS. 1A and 1B are explanatory views for explaining one embodiment of the present invention, in which reference numeral 24 is a cutting gap, 25 is a jet nozzle, and 26 is It represents a jet stream, and other symbols correspond to those in FIG.

The embodiment shown in FIG. 1 used for explaining the present invention corresponds to FIG. 5 used for explaining the phenomenon of generation of the free micromachining piece 22 at the beginning of the present specification. And the first
FIG. 2B is a bottom view taken along the arrow AA ′ in FIG. 1A and shows the state immediately before the loosened microfabricated piece 22 is loosened.

As described above, when the processing start position is the arrow position P ₃ shown in FIG. 1 (B), the wire electrode 5 moves in the direction of the arrow b shown in FIG. 1 and the wire electrode 5 is shown in FIG. 1 (B). As described above, when reaching the position P ₄ which is close to the processing start position P ₃ (the arrow Δd shown in this case is about 0.01 mm to 0.5 mm), the free micromachining piece 22 is displaced and the wire electrode 5 is moved.
A short circuit phenomenon occurs between the workpiece 1 and the workpiece 1. In this state, that is, just before the loosening, the loosened micro-machined piece 22 merely bridges the workpiece 1 by the portion indicated by the arrow Δd. And, as mentioned above, the above-mentioned arrow Δd is 0.01 mm.
Since it is about 0.5 mm, by applying an appropriate external pressure to the free microfabricated piece 22, the bridging portion is broken and the free microfabricated piece 22 can be easily separated from the workpiece 1. . The present invention uses the free piece removing means referred to in the present invention for the free micromachined piece 22 when the short circuit phenomenon occurs and the short circuit phenomenon is continued for a predetermined time (for example, about 5 msec to 1 second). External pressure is applied to force the free micromachining piece 22 to be processed 1
It is intended to be free from.

In the embodiment shown in FIG. 1 (A), a jet nozzle 25 is used as the free piece removing means, and the free micromachining is performed by a jet stream 26 (for example, air, electric discharge machining fluid) ejected from the jet nozzle 25. The piece 22 is forcibly excluded. That is, when it is detected that the above-mentioned short-circuit phenomenon continues for a predetermined time (the description is omitted because the detection means is well known to those skilled in the art), the jet nozzle 25 ejects the jet. Stream 26 is forced into cutting gap 24. By doing so, the free micromachining piece 22 in the state shown in FIG. 1 (B) can be easily separated from the workpiece 1. When jetting the jet stream 26, it is desirable to stop the power supply to the wire electrode 5 and retract the wire electrode 5 (to prevent disconnection of the wire electrode 5 when removing loose pieces).

As described above, it is possible to automatically and continuously detect the short-circuit phenomenon, forcibly remove loose pieces, and restart the electric discharge machining. Therefore, the actual cutting process is interrupted during this period, but the cutting process is substantially stopped. It can be thought that is performed continuously. Furthermore, in the above description, the present invention has been described by taking as an example the free micro-machined pieces that are generated when the back relief portion of the extrusion die is processed, but it goes without saying that the present invention is also applied to the case of other wire cut electric discharge machining. .

(Effects of the Invention) As described above, according to the present invention, it is possible to prevent the wire electrode from breaking due to the short circuit phenomenon of the wire electrode that occurs immediately before the loosened microfabricated piece, and the wire electrode can be prevented. Short-circuit detection, forced removal of loose pieces, and restart of electrical discharge machining are performed automatically in succession, so there is no manual interruption of machining when loose pieces occur, and virtually wire-cut electric discharge machining occurs even when loose pieces occur. Can be continued.

[Brief description of drawings]

FIG. 1 is an explanatory view for explaining an embodiment of the present invention, FIG. 2 is a configuration of an embodiment of an extrusion die manufacturing apparatus, and FIGS. 3 and 4 are examples of bearing hole shapes in the extrusion die, FIG. 5 shows an explanatory view for explaining the phenomenon of occurrence of loose microfabricated pieces. In the figure, 1 is a workpiece, 1-1 is an upper surface, 1-2 is a lower surface, 5
Is a wire electrode, 20 is a back relief portion, 22 is a free micromachining piece, 24 is a cutting gap, 25 is a jet nozzle, 2
6 represents a jet flow.

Claims (1)

[Claims] 1. A taper having a predetermined shape is formed by inclining the wire electrode with respect to a workpiece placed on the machining table based on movement information of the machining table using the wire electrode. In a wire-cut electric discharge machining method for cutting with a surface, a short-circuit detecting means for detecting the occurrence of a short-circuit is provided, and a jet nozzle for ejecting a liquid as a jet flow is provided, and the wire electrode is provided between the wire electrode and the workpiece. On the condition that a short circuit has occurred and that the short circuit has been detected for a predetermined period of time, the jet stream is jetted by the jet nozzle in a cutting gap at that time point to cause the short circuit. The wire-cut discharge is characterized in that pressure is applied to the micro-machined piece so that the micro-machined piece is released from the workpiece and eliminated. Construction method.