JPS5949851B2 - Electric discharge machining method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a method for accurately aligning a workpiece and a machining electrode in an electric discharge machining method, particularly in electric discharge machining in which the machining electrode is fed in an oblique direction. The present invention relates to an electrical discharge machining method.

As is generally known, electrical discharge machining equipment is used in a wide range of machining fields, 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. Therefore, when electrical discharge machining is performed on the mold as described above, the feeding direction of the machining electrode is fixed in the vertical direction, and the position of the machining electrode and the workpiece is adjusted by moving the machining table. Matching can be done easily. In addition, highly accurate alignment can be achieved by using, for example, optical alignment means. However, for example, the first
Figures to Figures 3 (Figure 1 is a side sectional view of one embodiment of a tire molding die, Figure 2 is a partially enlarged sectional view of the lower mold 2 in the embodiment shown in Figure 1, and Figure 3 is a side sectional view of an embodiment of the tire molding die. 2 Illustration missing marks A-N
The arrow B line shown in FIG.
(This line corresponds to the cross section shown in the figure.) Like the tire molding die shown in the figure, an upper mold 1 and a lower mold 2 each consisting of one block.
In order to manufacture, by electric discharge machining, a mold having, for example, a plurality of protrusions 3 to 7 which protrude on the cylindrical inner curved surface of each of the upper mold 1 and the lower mold 2. has been proposed by the inventors of the present application in the "Mold for Tire Molding Using Electrical Discharge Machining" (Japanese Patent Application No. 54-26919) and the "Electrical Discharge Machining Apparatus" (patent application filed on June 20, 1978). As shown, it is not enough to feed the processing electrode in only one direction. For example, taking the lower mold 2 as an example, in a plurality of radial directions (each of the plurality of radial directions) from the central axis of the lower mold 2, and further at angles in the directions of arrows a and b shown in FIG. It is necessary to process by changing the position direction.
That is, the entire area of the cylindrical inner circumferential surface of the lower mold 2 is divided into a plurality of parts and electrical discharge machining is performed, and the lower mold 2 that is finished by performing electrical discharge machining in the divided parts is shown in FIG. It must form a continuous pattern as shown. To achieve this, it is necessary to improve the alignment accuracy between the workpiece (lower mold 2) and the processing electrode during processing in each of the above directions. In cases such as molding molds, alignment of processing electrodes is extremely difficult. This is particularly difficult when the feeding direction of the processing electrode is oblique as in the direction of arrow b in FIG. Furthermore, since the processing electrode is worn out, it is necessary to replace it with a new electrode frequently depending on the degree of wear. Furthermore, in general, in electrical discharge machining, in order to improve machining efficiency, a method is often taken in which the machining electrode is replaced in stages during rough machining, semi-machining, and finishing machining. Therefore, in the electric discharge machining of the tire molding die, the machining electrodes are frequently replaced, and alignment of the machining electrodes becomes a problem each time the electrodes are replaced. In particular, in electrical discharge machining where the feeding direction of the machining electrode is diagonal as in the direction of arrow b shown in FIG. It is desired to perform positioning after giving the above-mentioned inclination, and there is a strong demand for means that can easily and accurately perform positioning of the electrodes. The purpose of the present invention is to satisfy the above-mentioned needs, and to easily and accurately align a workpiece and a machining electrode in electrical discharge machining that can be performed by feeding a machining electrode in an oblique direction. It is an object of the present invention to provide an electric discharge machining method equipped with an electrode positioning means that can perform the following steps.

This will be explained below with reference to the drawings. FIG. 4 is a front view and side view of an embodiment of an electrical discharge machining apparatus used to carry out the electrical discharge machining method of the present invention, and FIG. 5 is an explanatory diagram of the implementation process in one embodiment of the electrical discharge machining method of the present invention. It shows.

First, an embodiment of an electrical discharge machining apparatus equipped with a mechanism necessary for carrying out the electrical discharge machining method of the present invention will be described with reference to FIG. 4, 8 is the workpiece, 9 is the processing head, 10 is the spindle, 11 is the electrode attachment part, 12
13 is a processing electrode, 13 is a head support part, 14 is a drive part for rotating the head, 15 is a lifting block, 16 is a lifting screw, 17 is a column, 18 is a processing tank, 19 is a processing table, 20 is a drive part for rotating the table. , 21 represents a first table, 22 represents a second table, and 23 represents a bed. In FIG. 4, the processing head 9 drives a spindle 10 in the direction of arrow H in the figure by a drive device (not shown). A processing electrode 12 is attached to the spindle 10 via an electrode attachment part 11. The spindle 10 is driven in the direction of the arrow H in the figure to control the gap between the machining electrode 12 and the workpiece, which corresponds to predetermined machining conditions, such as extreme voltage, discharge current, etc. Along with this, the feed is controlled to always maintain and follow the feed constant (hereinafter referred to as automatic control feed). The processing head 9 is fixed to a head support part 13, and the head support part 13 is connected to a drive part 14 for rotating the head.
is rotatably supported in the direction of the arrow α shown in the figure.
Furthermore, the drive unit 14 for rotating the head is fixed to a lifting block 15 supported by a column 17 so as to be movable up and down in the direction of arrow Z in the figure by a lifting screw 16.
Go up and down with. Therefore, the angle with respect to the processing table 19 in the direction of the arrow H in the figure, which is the driving direction of the processing head 9, that is, the feeding direction of the processing electrode 12, is such that the head support portion 13 to which the processing head 9 is fixed is made rotatable. It is possible to set it to a desired value by Further, the heightwise positioning of the processing electrode 12 can be set to a desired heightwise position by raising and lowering the lifting block 15 in the direction of the arrow Z shown in the figure. Note that the rotation of the head support portion 13 in the direction of the arrow α in the figure and the raising and lowering of the lifting block 15 in the direction of the arrow Z in the figure can be carried out manually, electrically, or automatically controlled as necessary, although not shown. You can choose. On the other hand, the processing table 19 on which the workpiece 8 is placed can be rotated in the direction of the arrow β shown in the figure by a table rotation drive unit 20, and the table rotation drive unit 20 is fixed. By moving the first table 21 placed thereon in the direction of the arrow X shown in the figure, movement in the X direction is possible, and furthermore, the second table 21 placed slidably on the bed 23 can be moved in the X direction. By moving the table 22 in the direction of the arrow Y shown in the figure, movement in the Y direction is also possible.

The electrical discharge machining apparatus used to carry out the electrical discharge machining method of the present invention has been described above. This will be explained in relation to electric discharge machining of the lower mold 2 of the mold.

FIG. 5 is an explanatory diagram for explaining the electrode positioning process in one embodiment of the present invention, and only the portions of the electric discharge machining apparatus shown in FIG. 4 necessary for explaining the present invention are shown in an enlarged manner. . Reference numerals 8 to 12 and 19 in FIG. 5 correspond to those in FIG. Further, 24 is the rotation center line of the processing table 19, 25 is the horizontal upper surface of the workpiece 8, 26 is a reference jig, 2T and 28 are indicators, ? indicates the electrode reference point, and the sword indicates the processing completion reference point. The process of electrode alignment in the electrical discharge machining method of the present invention will be explained step by step with reference to FIGS. 4 and 5.

(1) First, when placing the workpiece 8 on the processing table 19, the center of the workpiece 8 and the center of rotation of the processing table 19 are made to coincide.

(2) Next, the related specifications for expressing the predetermined discharge start position of the machining electrode 12 are confirmed.

That is, I) feeding direction angle of processing electrode 12 (illustrated arrow angle θ
).

11) Feeding stroke of the processing electrode 12 (illustrated arrow l).

Iiii) When the machining electrode 12 is fed by the arrow l shown above, a predetermined reference point on the machining surface of the machining electrode 12? The position coordinate value of the machining completion reference point that is reached.

That is, the horizontal distance dl of the processing completion reference point knife with respect to the center line 24 of the workpiece 8 and the vertical distance HO3 with respect to the horizontal upper surface 25 of the workpiece 8) Next, the head rotation and drive shown in FIG. The inclination angle of the machining head 9, that is, the machining table 19, is adjusted by rotating the head support part 13 by the part 14.
The angle of the illustrated arrow I{direction with respect to the grapes is set to be θ.

4) Next, set the reference jig 26 for electrode positioning on the electrode mounting part 11.

In general, the reference jig 26 has a shape that allows a predetermined jig reference point, which serves as a position reference for the reference jig 26, to be accurately measured by a position measuring means such as an indicator. good. In the case of the present invention, as in the embodiment shown in FIG. 5, the reference jig 26 is supported by a support arm as shown in the figure for convenient position measurement of the jig reference point using the indicator 2T, which will be described later. I'm trying to use a sphere.

The center point of the sphere is set as the jig reference point. When setting the reference jig 26, make sure that the center point of the reference jig 26 is the electrode reference point. (Needless to say, the machining electrode 12 is set in the removed state.) In addition, in setting the reference jig 26, the electrode reference point is used to make the explanation easier to understand. I explained that the center point of the reference jig and the center point of the reference jig should be on a vertical line, but what about the electrode reference point above? It is only necessary to know the relative position between the reference jig 26 and the reference jig 26.
5) Next, the first table 21 illustrated in FIG.
By moving the second table 22 in the direction of the arrow X shown in the figure and the second table 22 in the direction of the arrow Y shown in the figure, the center point of the reference jig 26 is aligned with the rotation center line 24 of the processing table 19 (the center line of the workpiece 8 ) The processing table 19 is moved so as to match the position.

In order to confirm that the center point of the reference jig 26 and the table rotation center line 24 match, since the reference jig 26 is spherical, the processing table 19 is rotated in the direction of the arrow β shown in the figure, for example. The position can be set accurately by measuring whether the indicator 27 attached to the processing table 19 correctly slides on the spherical circumferential surface of the reference jig 26. Note that the processing head 9 at this time may be set at an arbitrary height from the workpiece 8. (6) Next, move the first table shown in FIG. 4 to the right to move the reference jig 26 to the position indicated by the arrow (1) in FIG. 5 relative to the workpiece 8. Move from to () position.

The moving distance D2 is a numerical value expressed by the following equation.
That is, D2=d1-{l+(H1-H2)}COSθwhere, H, is the vertical distance of the electrode reference point 4 to the electrode mounting portion 11, and H2 is the vertical distance of the reference jig 26 to the electrode mounting portion 11. (7) Next, the processing head 9 is lowered by vertically lowering the lifting block 15 shown in FIG.
from the position shown in the figure to the position shown by the arrow (1).

The position of the illustrated arrow (l) refers to the position where the center point of the reference jig 26 is on the extended surface of the horizontal upper surface 25 of the workpiece 8. Whether or not the reference jig 26 is in the position indicated by the arrow () in the figure can be determined by looking at the indicator 2 from the horizontal upper surface 25.
8, the position can be confirmed accurately. (8) Next, in the same manner as in (7) above, the reference jig 26
Move the position from arrow (1) to arrow (5) in the figure.

The moving distance D2 is expressed by the following equation. That is, D3=
h−{l+(H1−H2)}Sinθ The position obtained through the above-described steps (1) to (8) becomes the predetermined electric discharge machining start position of the machining electrode 12.

That is, in a state where the process (8) above is completed (hereinafter this position will be referred to as the machining start origin), the reference jig 26 is removed, the machining electrode 12 is set, and electrical discharge machining can be started. Incidentally, even if the machining head 9 is raised to replace the electrode, for example, if the distance of elevation is memorized, it is easy to return it to the machining starting point after replacing the electrode.
In this way, once the machining start origin is obtained through the steps (1) to (8) above, the workpiece 8
If all relative movements between the workpiece 8 and the machining head 9 are performed based on the machining start origin, the workpiece 8
It is easy to return the relative positional relationship between the machining head 9 and the machining head 9 to the machining start origin. As explained above, according to the present invention, it is possible to easily align the workpiece and the machining electrode in electric discharge machining in which the machining electrode is fed in an oblique direction, and the alignment accuracy can be improved. It is possible to provide an electric discharge machining method equipped with a high electrode positioning means.

Further, the present invention can exhibit its effects even more significantly in the above-mentioned electric discharge machining in which electrodes are replaced frequently. By locating the absolute coordinate position (with respect to the processing device) of the jig reference point on the reference jig, subsequent alignment to the processing start origin can be performed automatically, for example, by NC. Needless to say.

[Brief explanation of the drawing]

Fig. 1 is a side sectional view of one embodiment of a tire molding mold, Fig. 2 is a partially enlarged sectional view of the lower mold in the embodiment shown in Fig. 1, and Fig. 3 is an arrow A-A shown in Fig. 2. 4 is a front view and a side view of one embodiment of the electrical discharge machining apparatus used in the present invention, and FIG. 5 is a developed plan view of one embodiment of the electrical discharge machining method of the present invention. An explanatory diagram of the implementation process is shown. In the figure, 8 is a workpiece, 9 is a processing head, 10 is a spindle, 11 is an electrode mounting part, 12 is a processing electrode, 13 is a head support part, 14 is a drive part for rotating the head, 15 is a lifting block, 16 is a lifting screw, 17 is a column, 18 is a processing tank, 19 is a processing table, 20 is a table rotation drive unit, 21 is a first table, 22 is a second table, 23
is the bed, 24 is the table rotation center line, 25 is the horizontal upper surface of the workpiece 8, 26 is the reference jig, 27 and 28 are indicators, 3 is the electrode reference point, and the base is the machining completion reference point. .

Claims (1)

[Claims] 1. At least a processing table that is movable in the front-rear and left-right directions and on which a workpiece is placed, and a processing head that is movable up and down and capable of feeding a processing electrode in an oblique direction, In the electric discharge machining method in the electric discharge machining apparatus for electric discharge machining the workpiece, the electric discharge of the machining electrode is performed by feeding the machining electrode relative to the workpiece by a predetermined distance. When setting the machining electrode at the machining start position, (a) with the machining electrode removed from the electrode attachment part of the machining head, set the reference point on the reference jig relative to the electrode attachment part; A process of setting a reference jig having a spherical body with the jig reference point at the center of the spherical body as a reference jig for locating the discharge start position, (b) setting the feeding direction of the processing head in the diagonal direction; While the reference jig is set at an angle, the jig reference point on the reference jig held in the electrode mounting part and the reference vertical line perpendicular to the predetermined table reference point on the processing table are aligned in advance. A process of matching the predetermined relationship, (c) Determining the distance between the jig reference point and the predetermined electrode reference point on the machining electrode when it is assumed that the machining electrode is attached instead of the reference jig. Taking into consideration, the process of setting the processing head to the processing start origin,
(d) Using the machining start origin as a reference, move the machining head to a desired position or remove the reference jig without moving and attach the machining electrode, and then perform electrical discharge machining in the diagonal direction. A method for electrical discharge machining, characterized in that: