JPS5949850B2 - Electric discharge machining method using electric discharge machining equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides an electrical discharge machining method using an electrical discharge machining device, and in particular, enables setting of a feeding angle of a machining electrode and relative positioning of the machining electrode and a workpiece, and enables the above-mentioned machining. The processing head for feeding the electrode is composed of a first processing head and a second processing head fixed to the tip of a spindle of the first processing head, and the first processing head and the second processing head are connected to each other. The table rotation drive unit that rotates the processing table uses an electric discharge machining device having a servo drive mechanism, and has a larger recess than the so-called first processing electrode that processes the protrusion of the workpiece. The present invention relates to an electrical discharge machining method for machining the root portion of a protrusion in a manner that wraps the protrusion using a second machining electrode.

As is generally known, electrical discharge machining equipment is used in a wide range of machining fields by taking advantage of the excellent features of electrical discharge machining.

In particular, it is possible to process efficiently regardless of the mechanical properties of the workpiece, such as hardness, tensile strength, work hardening properties, etc., and even when processing complex shapes, it is possible to use electrodes with a shape that corresponds to the shape to be machined. It is widely used in the mold processing field because it allows high-precision processing. In general, in electrical discharge machining, which involves machining molds such as cutting dies, drawing dies, and forming dies, all of the machining surfaces of the mold can be viewed from one direction.
The processing electrode may be fed in only one predetermined direction. However, for example, in order to manufacture a mold having multiple protrusions that protrude almost perpendicularly on a curved surface, such as a tire mold, by electrical discharge machining, the machining electrode must be fed in only one direction. However, it is necessary to change the position of the tire in a plurality of directions radially from the center of the tire molding die, and further in a plurality of angular positions in each of the plurality of radial directions (
Note that it goes without saying that it may be necessary to replace the machining electrodes used for machining in each of the above directions. The need to be able to change the feed direction of the machining electrode as described above when manufacturing the tire molding die by electric discharge machining will be explained with reference to FIGS. 1 to 3. FIG. 1 is a side sectional view of one embodiment of a tire molding mold, FIG. 2 is a partially enlarged sectional view of a lower mold in the embodiment shown in FIG.
A developed plan view taken along the arrow AA' in the figure is shown.
In the figure, 1 is the upper mold, 2 is the lower mold, 3 is the contour surface and corresponds to the ground contact surface of the tire, 4 is the shoulder part, and 5 to 9 are the protrusions. Parts 6 and 8
protrudes almost perpendicularly to the curved surface of the contour surface 3.
Further, PL is the parting line, which is the joint surface between the upper mold 1 and the lower mold 2, CL is the center line, which is the center line of the contour surface 3, and the arrow B line shown in FIG. 3 is shown in FIG. Lines corresponding to the cross sections are shown. Generally, a tire molding mold is composed of an upper mold 1 and a lower mold 2 as shown in FIG. The tire molding inner circumferential surface of each mold is formed with a concavo-convex surface having a complicated shape as shown in FIGS. 2 and 3, for example. In order to mold the upper mold 1 or the lower mold 2 by electric discharge machining, a machining electrode having an uneven shape opposite to that of the upper mold 1 or the lower mold 2 is used. However, in general, a plurality of substantially perpendicular grooves are often formed on the ground contact surface of a tire. That is, as shown in FIG. 2, which shows a side cross section of the lower mold 2, for example, protrusions 6 and 8 are provided which are formed to protrude substantially perpendicularly to the contour surface 3. As in the embodiment shown in FIG. 2, when two or more protrusions are provided that protrude perpendicularly to the contour surface 3, no matter which angular position the electrode is fed in, the protrusions If it is attempted to process parts 6 and 8 at the same time, it is inevitable that one or both of the protrusions will be overcut. Therefore, the inventors of the present invention have proposed a manufacturing system for tire molding molds by electric discharge machining (Japanese Patent Application No. 1982-26919).
Accordingly, first move the machining electrode (not shown) in the direction shown by the arrow a in the second figure.
Then, the machining electrode is replaced and the machining electrode is fed in the direction of the arrow b shown in Figure 2 to perform electrical discharge machining (the machining order is changed to direction, then a direction). Furthermore, since the inner peripheral surface of the tire molding mold is cylindrical, the electrical discharge machining is performed on the inner peripheral cylindrical surface of the tire molding mold in a range corresponding to the size of the machining surface of the machining electrode. It is necessary to perform the processing separately, and it is necessary to freely select the feeding direction of the processing electrode relative to the inner cylindrical surface in a radial direction. That is, in order to manufacture the above-mentioned tire molding die by electrical discharge machining, it is possible to freely set the machining electrode feeding angle and to freely align the machining electrode and the workpiece relative to each other. There is a strong desire for an electric discharge machining apparatus configured as described above. Further, as is generally known in electrical discharge machining, electrode wear to a greater or lesser degree is an unavoidable problem.

FIGS. 4A to 4C show an example of the electrode wear process as the machining progresses. In the figure, E represents a processing electrode, and W represents a workpiece. As illustrated in FIG.
The machining electrode E shown in Figure A before machining wears out as the machining progresses, as shown in the machining electrode E shown in Figures 4B and 4C. As shown in the figure, the corners are particularly worn out, and the corners are rounded and r-shaped. Therefore, it is difficult to process the workpiece W shown in FIG. 4A into a shape having corners without r, as shown by the dotted lines. In order to perform this processing, it is necessary to perform finishing processing on the workpiece W shown in FIG. 4C using a new processing electrode E shown in FIG. 4A. In order to finish the shape with sharp corners as indicated by the dotted line in FIG. 4A, it is necessary to repeat the finishing process many times by replacing the machining electrode E with a new one. Therefore, in order to finish one workpiece W into the desired shape, a large number of processing electrodes E (shown in FIG. 4A) must be prepared. The present invention
In order to solve the above problems, the electric discharge is designed to be able to set the feed direction angle of the machining electrode and to align the machining electrode relative to the workpiece, as well as having corners without r. It is an object of the present invention to provide an electric discharge machining method that uses an electric discharge machining device that facilitates machining and that can perform desired machining while minimizing the number of electrode replacements.

This will be explained below with reference to the drawings. 5A and 5B are a front view and a side view showing one embodiment of the electrical discharge machining apparatus used in the present invention, and FIG. 6 is an enlarged view of related parts to explain the operation of the machining head and machining table in FIG. 5. figure,
FIG. 7 is a diagram showing an example of a processing process for explaining the corner forming processing without r in the present invention.

In the figure, 10 is the workpiece, 11 is the first machining head in the direction of the arrow H in the figure, 11' is the pulse motor of the first machining head 11, 12 is the spindle of the first machining head 11, 13 is the second processing head 13' in the direction of the arrow h shown in the figure.
14 is a processing electrode mounting jig, 15 is a processing electrode, 16 is a head support part that supports the first processing head 11, and 17 is a drive part for rotating the head. 18, which rotates the head support part 16 together with the first processing head 11 in the direction of the arrow α shown in the figure;
is an elevating block supported by a column 20 so as to be movable up and down in the direction of arrow Z in the figure by means of an elevating screw 19;
21 is a processing tank, 22 is a processing table, and the workpiece 1
0 is placed, 23 is a table rotation drive unit that rotates (servo drive) the processing table 22 in the direction of the arrow θ shown in the figure, for example by a pulse motor or hydraulic pressure, and 24 is a first table rotation drive unit. The processing table 22 together with the table rotation drive unit 23 is
25 is a second table that moves the first table in the direction indicated by the arrow Y;
Each number 6 represents a bet. In FIG. 5, which shows one embodiment of the electrical discharge machining apparatus used in the present invention, a machining head 11 drives a spindle 12 in the direction of arrow H in the figure by a pulse motor 11'.

A second machining head 13 is fixed to the tip of the spindle 12, and the second machining head is connected to a pulse motor 1.
37, the processing electrode 15 is driven in the direction of the arrow h in the figure via the electrode mounting jig 14. The operation of the second processing head 13 will be described later, but will be explained here assuming that the second processing head 13 is in a stopped state. The spindle 12 is driven by the pulse motor 1 of the machining head 11 in the direction of the arrow H shown in the figure.
5 and the workpiece 10 is controlled to always maintain and follow the gap as the machining progresses (hereinafter referred to as automatic servo drive). Note that the first and second processing heads 1
Instead of the pulse motors 11', 13' for driving L13, other automatic servo drives such as hydraulic servos may be used. That is, the electrical discharge machining apparatus used in the present invention shown in FIG. The angle of the machining head 11 in the direction of the arrow H, that is, the machining table 2
The automatically controlled feed direction angle of the machining electrode 15 relative to the workpiece 10 can be set to a desired angle, and the machining position when the machining electrode 15 performs electrical discharge machining on the workpiece 10 can be set as desired.

Furthermore, the electric discharge machining apparatus of the present invention will be explained in connection with electric discharge machining of the lower mold 2 of the tire molding mold shown in FIGS. 1 to 3.

First, the center of the workpiece 10 formed by, for example, machining, leaving a machining allowance due to electrical discharge machining (minimum machining allowance is good for performing electrical discharge machining efficiently), is located in the θ direction of the machining table 22. As shown in FIG. 5, the workpiece 10 is placed on the processing table 22 so as to coincide with the center of rotation.

Next, the workpiece 10 is moved to a predetermined position relative to the processing head 11 by moving the first table 24 and the second table 25 in the directions of the arrows X and Y shown in the figure. Set. For example, when electrical discharge machining is performed on the lower mold 2 as shown in FIG. Therefore, electrical discharge machining will be performed. First, for example, if we start machining in the direction of arrow b shown in FIG. 2, we turn the head support part 16 so that the direction of arrow H shown in FIG. Move and set. Next, the lifting block 18 is lowered to set the processing electrode 15 at a predetermined position. As described above, after the machining electrode 15 and the workpiece 10 are aligned, the machining electrode 15 is automatically controlled and fed to perform electrical discharge machining.
It goes without saying that during the electrical discharge machining, the workpiece 10 is immersed in a machining liquid (not shown) supplied into the machining tank 21. Then, when the feeding stroke of the machining electrode 15 in the H direction in the electric discharge machining reaches a predetermined depth, the electric discharge machining is interrupted and the machining electrode 15 returns to its original position before machining. The portion machined by the electrical discharge machining described above is limited to the portion corresponding to the machining surface of the machining electrode 15. Therefore, the processing table 22 is rotated by a predetermined angle in the direction of the arrow θ in the figure by the table rotation drive unit 23, and then the processing electrode 15 is rotated by a predetermined angle.
Replace or perform electrical discharge machining again without replacing. In this way, the machining table 22 is sequentially rotated to perform electrical discharge machining. When the machining table 22 rotates once and the electric discharge machining in the direction of the arrow b in FIG. 2 is completed, for example, the electric discharge machining in the direction of the arrow a in FIG. 2 is performed next. In the electric discharge machining, the machining electrode 15 is prepared in advance as described above.
In addition to replacing the electrode with one for directional machining, the feeding direction of the machining electrode 15 must be corrected to the above-mentioned direction a. That is, by rotating the head support part 16 in the direction of the arrow α in the figure, the direction of automatically controlled feeding of the processing head 11 (the direction of the arrow H in the figure) is changed to the second direction.
It should be parallel to the direction of arrow a shown in the figure. Then, the machining table 22 is rotated to perform electrical discharge machining in the same way as the electrical discharge machining in the direction b shown in FIG. 2 described above. By performing electric discharge machining on the workpiece 10 as explained above,
A lower mold 2 of a tire molding mold as shown in FIGS. 1 to 3 is manufactured.

In the electric discharge machining, the machining electrode 15 is worn out due to electric discharge, so it goes without saying that it is necessary to replace it with a new electrode depending on the degree of wear. Further, the controlled feeding of the machining electrode 15, the drive of the machining table 22, etc. in the electric discharge machining are automated by predetermined program control, so that the electric discharge machining is automatically performed. Further, in electric discharge machining, as described with reference to FIG. 4 at the beginning of this specification, electrode wear occurs as the machining progresses. Particularly, the electrode consumption occurs significantly at the corners of the electrode shape. Therefore, in order to form a corner without r, in the electrical discharge machining apparatus of the present invention, as shown in FIGS. 5 and 6, the pulse motor 13'
The processing table 22, which is equipped with a second processing head 13 that is automatically servo-driven by the machine and on which the workpiece 10 is placed, is automatically servo-driven by a table rotation drive unit 23. . That is, as shown in FIG. 6, the first processing head 11 (spindle 1 shown in FIG.
The second machining head 13 fixed at the tip of the
The machining electrode 15 is automatically servo driven by the motor 13' via the electrode mounting jig 14 in the direction of the arrow h in the figure. Further, the processing table 22 is automatically servo driven in the direction of the arrow θ shown in the figure by a table rotation drive unit 23 (see FIG. 5). As shown in FIG. 7A, it is assumed that the machining electrode 15 is automatically servo-driven in the direction of the arrow H in the figure to perform electric discharge machining on the workpiece 10 to finish it into the shape shown by the dotted line in the figure.

However, as shown in FIG. 7B, the corners of the processing electrode 15 become rounded due to electrode wear. Therefore, the workpiece 10
However, the desired shape as shown by the dotted line in FIG. 7A is not obtained, and the corners are rounded. Therefore, as shown in FIG. 7B, the side wall of the concave portion 15' of the processing electrode 15 is cut off to expand it until the dotted line shown in the figure, that is, the r of the corner portion disappears. d in the figure shows the expansion width. Actually, an expanded machining electrode is created in advance and this machining electrode is used.
Furthermore, even when using this expanded processing electrode,
Since the right and left root portions of the protrusion 1'' shown in FIG. 7C are processed at once, the number of electrode replacements is reduced compared to the case where electrodes are used to process individual root portions. Next, as shown in FIG. 7C, after the processing electrode 15 is sent a predetermined distance in the direction
The corner marked r is removed by automatic servo driving by a distance d in one direction of the arrow h shown in the drawing by the second processing head 13 shown in the drawing.

Thereafter, the processing electrode 15 is moved a distance 2 in the other direction of the h direction.
The other corner with r is machined by automatic servo driving by d. As a result, the protrusion 1' of the workpiece 10 is
It is possible to finish the shape into a shape having corners without r as shown by the dotted line in the figure. H of the machining electrode 15 in the above electric discharge machining
The feeding distance in the direction and the h direction can be set within a predetermined range using, for example, a limit switch. That is, the automatic servo drive in the direction of the arrow H shown in FIG. After stopping the feeding in the H direction, the automatic servo drive in the H direction is started, and this drive is performed by the second processing head 13. and,
In the machining in the h direction, if a short circuit occurs between the electrode 15 and the workpiece 10, the machining electrode 1
5 is moved back by a predetermined distance in the direction of arrow H and in the opposite direction to the direction of arrow h. The retraction distance can also be set, for example, by presetting the number of pulses sent to the processing head. Note that, after the processing electrode 15 is once retreated, processing is continued by first feeding it in the H direction and then feeding it in the H direction again. The retreating operation of the processing electrode 15 may be performed by simultaneously performing the retreating in the H direction and the h direction, or by starting the retreating in the h direction first and then starting the retreating in the H direction. good. Furthermore, although not shown in the drawings, if the corner with the r mentioned above exists in a direction parallel to the surface of the processing table 22, the processing table 22 is automatically servo driven in the θ direction shown in FIG. Corners can be finished without r.

In this case, instead of the automatic servo drive of the machining electrode 15 in the direction of the arrow h shown in the figure by the second machining head 13, which explained the relative movement between the machining electrode 15 and the workpiece 10 in FIG. This is done by automatic servo driving in the θ direction, and the machining process does not change in any way and can be easily understood, so a detailed explanation will be omitted. The electrical discharge machining method for forming a corner without r in the direction parallel to the arrow h direction or θ direction shown in FIG. 6 has been described above, taking the electrical discharge machining of a tire molding die as an example.

However, in general, for example, in the tire molding mold described above, the corners without the r do not necessarily exist only in the direction parallel to the h direction or the θ direction, but usually exist in any direction as well. be. Therefore, when machining a corner without r that exists in any direction, automatic servo driving of the second machining head 13 in the direction of the arrow h shown in FIG. The automatic servo drive in the direction of the arrow θ shown in the figure is made to run in parallel at the same time, and the automatic servo drive speed of the husband in the h direction and the θ direction is changed to the same or alternately to correspond to the above arbitrary direction. By doing so, it is possible to form a corner portion having no r in a desired direction. It goes without saying that the linked operation between the automatic servo drive in the direction of the arrow H in FIG. 6 and the automatic servo drives in the h and θ directions in this machining is performed in the same manner as described with reference to FIG. stomach. As explained above, according to the present invention, it is possible to set the feeding direction angle of the machining electrode and to align the machining electrode and the workpiece relative to each other, and also to perform electrical discharge machining of a shape having corners without r. It is possible to provide an electrical discharge machining method using an electrical discharge machining device that can easily perform the following steps.

[Brief explanation of drawings]

FIG. 1 is a side sectional view showing one embodiment of a tire molding die;
Fig. 2 is a partially enlarged view of the lower mold in the embodiment shown in Fig. 1, Fig. 3 is a developed plan view taken along arrows A and A' in Fig. 2, and Fig. 4 is an electric discharge machining diagram for explaining electrode wear. FIG. 5 is a front view and plan view of one embodiment of the electric discharge machining apparatus of the present invention, and FIG. 6 is a diagram showing the machining process in the embodiment shown in FIG. FIG. T is an enlarged view of related parts for explaining the operation of the head and the processing table, and is a view showing one embodiment of the processing process for explaining the corner forming processing without r in the present invention. In the figure, 10 is the workpiece, 10' is the protrusion formed on the workpiece 10, 11 is the first machining head, 11' is the pulse motor, 12 is the spindle, and 13 is the second machining head. A machining head, 13' is a pulse motor, 14 is an electrode mounting jig, 15 is a machining electrode, 15' is a recess provided in the machining electrode 15, 16 is a head support part, IT is a drive part for rotating the head, 18 is a 19 is a lifting screw, 20 is a column, 21 is a processing tank, 22 is a processing table, 23 is a table rotation drive unit, 24 is a first table, 25 is a second table, and 26 is a bed. ing.

Claims (1)

[Scope of Claims] 1. A machine that corresponds to the shape of the workpiece and has a processing table on which the workpiece is placed and a processing head that feeds the processing electrode, and has a protrusion protruding from the surface. Using a machining electrode having a concavity formed from the surface thereof, an electric discharge machining device configured to perform machining of the workpiece using electric discharge energy in a manner corresponding to the concavity of the machining electrode. In the electric discharge machining method, the electric discharge machining apparatus includes a first machining head and a first machining head fixed to the tip of a spindle of the first machining head and feeding in a direction crossing a feeding direction by the first machining head. a second processing head, a head support section that supports the first processing head, a head rotation drive section that rotatably supports the head support section, and a processing table on which the processing table is mounted. At least the first processing head, the second processing head, and the table rotation drive section have a servo drive mechanism to feed the first processing head. The second processing head and/or the processing table is configured to be controlled and driven within a predetermined distance by the servo drive mechanism on condition that the position reaches a predetermined position. Ori,
Furthermore, after the processing is performed using the processing electrode, a cross-sectional area of the opening of the recess corresponding to the cross-section of the root is formed to be larger than a cross-sectional area of the root of the protrusion of the workpiece processed by the processing electrode. A control drive is activated for the second processing head and/or the processing table using the second processing electrode, so as to process a root portion of the protrusion in a shape that wraps around the protrusion. A method of electrical discharge heating using an electrical discharge machining device characterized by: 2 When a short circuit occurs between the second processing electrode and the workpiece during control within the predetermined distance range, the first processing head and the second processing head and/or Alternatively, the machining table is retracted by a predetermined distance in the counter-feeding direction, and the electric discharge machining is started again from the retracted position. Electric discharge machining method using electric discharge machining equipment. 3 The backward movement of the first processing head in the counter-feeding direction is as follows:
3. The electric discharge machining method using the electric discharge machining apparatus according to claim 2, wherein the electric discharge machining method is started after the start of the backward movement of the second machining head and/or the machining table.