JPS6048292B2 - Electric discharge machining control method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electrical discharge machining method, and particularly to machining control when applying an auxiliary displacement between a machining electrode and a workpiece with an element in a direction orthogonal to the direction in which the two approach each other. Regarding the method.

The above-mentioned auxiliary displacement is usually applied to the machining electrode or the workpiece for the purpose of obtaining a highly accurate similarity between the machining milk shape and the machining electrode cross-sectional shape, or for other purposes.

A conventional method of providing this auxiliary displacement will be described with reference to FIGS. 1-5. In Fig. 1, a machining electrode 1 with a triangular cross section is caused to make circular motion (revolutionary motion) with a radius indicated by 2, and as a result, the apparent cross-sectional shape of the electrode is caused by a radial movement at the corner of the triangle, as indicated by 3. Because it has a shape that connects arcs,
A similar processed hole 5 is formed in the workpiece 4. In this machining method, it goes without saying that the cross-sectional shape of the machining electrode 1 and the machining hole 5 do not have similar shapes. Figures 2 and 3 show that a machining electrode 6 with a square cross-sectional shape is given a similar movement locus 7 along the electrode shape, that is, a square periodic motion, and its position is changed as shown by the arrow. is expanded step by step every cycle. According to this method of applying the auxiliary displacement, in principle, a machining hole 8 having a similar shape to that of the machining electrode 6, which is an enlarged cross-sectional shape, is formed in the workpiece 4.
However, in this machining control, since the direction of the periodic motion 7 is always constant, when the machining electrode 6 moves, the part where the electric discharge occurs is constant, facing the new machining part, and as a result, the machining electrode has no effect on the electric discharge. Local electrode wear 9 occurs only on one side of the corner, and a machining residue 10 corresponding to the electrode wear 9 occurs in the machined hole 8, making it impossible to obtain an accurate square machined hole. arise. Furthermore, FIG. 4 shows another periodic motion locus 11 imparted to the machining electrode 6 having a square cross-sectional shape.
After moving a certain distance in the a) direction, it returns to point P, then similarly moves in the directions (b), (c), and (d), and then returns to point P by drawing a square trajectory 11a. .

The amount of movement in the directions (a) to (d) is sequentially expanded, and accordingly, the square locus 11a is also expanded. According to this control method, the local electrode wear that occurs on the machining electrode and the resulting amount of machining residue on the workpiece are improved to some extent compared to the case shown in Fig. 2, but the square motion Locus 11
It is undeniable that the same tendency as in the case of FIG. 2 occurs due to a. Furthermore, in this control method, the processing electrode 6 repeatedly moves in the radial direction from the origin P, so there is a lot of waste in the operation.
FIG. 5 shows this situation, and shows the amount of movement f of the processing electrode 6.
Since the ratio of the electric discharge machinable range e to the machining area e is small, a large amount of time is spent simply moving the machining electrode 6, resulting in a disadvantage that the machining time becomes long. Note that g indicates a discharge gap. The present invention solves the problems of such conventional devices,
In particular, it eliminates the disadvantage of uneven electrode wear of the machining electrode, and by reversing the direction of the periodic movement of the auxiliary displacement given between the machining electrode and the workpiece as machining progresses, the machining electrode can be made wider. The feature is that the parts are efficiently used for electrical discharge machining, thereby preventing extreme local wear.

To explain the illustrated example, in FIGS. 6 and 7,
P is the center of the processing electrode, and the line indicated by the reference numeral 12 and the arrow attached thereto indicate the locus of periodic motion. That is, the processing electrode 6 moves in the radial direction from point P, reaches point h, and from there draws a square locus clockwise in the figure. (h)
Returning to the point, it moves in the radial direction again until it reaches point (i), and this time draws a square locus that is enlarged counterclockwise, and each time the amount of movement is enlarged, the direction of periodic motion is similarly changed. I will change it. In addition to reversing the direction of this periodic motion every cycle as described above, it can also be done every few cycles, especially if the number of cycles required to complete machining is large. Can also be done. When machining is performed by sequentially reversing the direction of the periodic motion in this way, the sides on both sides of the corner of the machining electrode 6 are effectively used for electrical discharge machining, so they wear out evenly as shown in FIG. 8, for example. do.

Therefore, - the service life of the machining electrode 6 becomes longer, and the amount of electrode wear 9 is averaged out and smaller than in the case of FIG. FIG. 9 shows an upper (
The figure below shows an example of a device for imparting relative motion.

14 is an X-axis table on which the workpiece 4 is placed and fixed, and 15 is a Y-axis table for moving this X-axis table 14 in the Y-axis direction, which are driven by an X-axis motor 16 and a Y-axis motor 17, respectively. .

The processing electrode 6 is controlled to move up and down in the Z-axis direction by a lift cylinder 18 and a hydraulic servo valve 19 that controls the lift cylinder 18. 20 is a numerical control device which receives a signal from an information tape 21 regarding auxiliary displacement and a lift signal n, and controls the hydraulic servo valve 19 and the X) and Y-axis motors 16 and 17 based on these signals.

That is, a signal is given to the hydraulic surf valve 19 to bring the machining electrode 6 close to the workpiece 4 and hold it at a predetermined height position by the lift signal n, and the machining electrode 6 at that position is then , , the Y-axis motors 16 and 17 are used to provide a planar auxiliary displacement movement to the workpiece 4.
This auxiliary displacement may be performed using the trajectories shown in FIGS. 6 and 7, or other trajectories, and such numerical control can be easily performed using well-known techniques. In addition, the 6th
It is clear that Fig. 7 shows only one example of the locus of the periodic motion of the auxiliary displacement and the reversal locus of its direction, and the reversal of direction can be performed for any other periodic motion. .

For example, in the periodic motion shown in Figure 4, the locus 1 of the square
If only the direction 1a is reversely changed each time the amount of movement increases, the same effect as described above can be obtained. As described above, the present invention sequentially reverses the direction of periodic motion during auxiliary displacement, so each side of the machining electrode can be effectively used for electrical discharge machining, and therefore local High-precision machining can be performed with as little electrode wear as possible.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing an example of a conventional auxiliary displacement between a machining electrode and a workpiece, and FIGS. 2 and 4 are diagrams showing examples of periodic motion trajectories of other conventional auxiliary displacements, respectively. Figure 3 is a plan view showing an example of wear of the machining electrode and generation of machining residue on the workpiece;
FIG. 5 is a longitudinal sectional view showing the machining state in the auxiliary displacement shown in FIG. 4, FIG. 6 is a line diagram of a periodic motion locus showing an example of setting the auxiliary displacement according to the present invention, and FIG. 7 is the part shown in FIG. 6. Enlarged view, No. 8
The figure is a plan view corresponding to FIG. 3 showing an example of electrode wear and machining residue when processed by the method of the present invention, and FIG. 9 is a perspective view showing an example of an apparatus for carrying out the method of the present invention. be. 4... Workpiece, 6... Machining electrode,
12... Periodic motion locus.

Claims (1)

[Claims] 1 An electric discharge machining method in which an auxiliary displacement is applied between the machining electrode and the workpiece, with an element in a direction perpendicular to the direction in which the two approach each other, and this auxiliary displacement is a periodic motion in which the amount of displacement is expanded in stages. An electric discharge machining control method characterized in that the direction of the periodic motion in the auxiliary displacement is sequentially reversed.