JPS601128B2 - Electric discharge machining method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electric discharge machining method, and more specifically,
The present invention relates to an electrical discharge machining method for machining the cross-sectional contour of a workpiece into at least a partial circular or elliptical shape.

Generally, as shown in FIG. 1, electrical discharge machining is performed so that the contour line a of the workpiece 1 has a shape including a part of a circle or an ellipse according to a predetermined formula ax2+by2=r2. A situation arises where this is required.

To meet such processing requirements, for example, if a cylindrical rod-shaped electrode is used and the electrode is moved relative to the workpiece along a desired circular or elliptical locus using an NC control device, the contour of the desired circle or ellipse can be obtained. shape can be obtained. However, in such a machining method, the dimensions of the electrode differ between the start of machining and the end of machining due to wear of the electrode, so no matter how precisely the machining electrode is moved along the required circular or elliptical trajectory, However, it was difficult to process the workpiece to exact dimensions. Therefore, it has been considered to perform electric discharge machining by non-consumable machining, but non-consumable machining has the disadvantage that the machining speed is slow and therefore the machining efficiency is significantly reduced. The present invention has been made in view of the above-mentioned drawbacks of the prior art, and its purpose is to form a cross-sectional profile of a workpiece into a required circular or elliptical shape with a low LI at a high processing speed and with high precision. It is an object of the present invention to provide an electrical discharge machining method that can easily perform electrical discharge machining into some shapes. In the following, the method of the invention will be explained in detail with reference to the illustrated embodiments.

Referring to FIG. 2, a workpiece 1 has been rough-finished in advance by an appropriate means into a contour shape that includes a shape approximately corresponding to the shape of a part of the desired elliptical shape indicated by the double dotted line. A case is shown in which a flat plate-shaped processing electrode 2 is used to precisely process a material into a desired shape including a part of the above-mentioned elliptical shape by the method of the present invention.

The workpiece 1' is placed on the machining table 3 so that its electric discharge machining part protrudes from the machining table 3, and the machining table 3 is moved at least within the X-Y plane parallel to the plane of the paper by a guide support member (not shown). It is supported so as to be movable in the Y-axis direction. In order to control the feeding of the processing table 3 along the Y-axis direction, a screw 5 that is rotationally driven by a driving pulse motor 4 is screwed into the processing table 3, and controls the rotation of the pulse motor 4. By doing so, the processing table 3 can be moved by a desired distance in a desired direction along the Y-axis direction. On the other hand, processing electrode 2
has a flat surface 6 that forms an electrical discharge machining gap with the workpiece 1, and this machining electrode 2 is connected to a spindle (not shown) provided on a machining head (not shown) of the electrical discharge machining apparatus main body. The processing electrode 2 is attached to the spindle so that the rotation axis 7 of the spindle is included in the flat surface 6 which is the discharge surface, and the rotation axis 7 is perpendicular to the x-x plane. It has been adjusted accordingly. Rotation of the spindle is provided by rotation of a pulse motor 8 housed in a processing head (not shown), thereby rotating the processing electrode 2. Next, while rotating the processing electrode 2 around the rotation axis 7, the workpiece 1 is caused to move along the Y-axis direction in relation to the rotational movement of the processing electrode 2. The electrical discharge machining gap formed between the workpiece surface 9 and the flat surface 6 is moved along the planned machining line of the workpiece, and the contour shape of the workpiece 1 is changed to a contour shape including the planned elliptical shape. The processing method will be explained in detail.

The elliptical shape to be machined shown on the workpiece 2 is expressed as ax2+by2=r2 ......{1}, and on the other hand, the projection line of the flat surface 6 of the processing electrode 2 onto the x-Y plane is expressed as y2kx11......■, and the conditions for the flat surface 6 of the processing electrode 2 to be in contact with the contour surface defined by the elliptical shape of the workpiece to be processed are as follows:
If we take k=tan and find it, according to the teachings of algebra, [3'l=shizo aCOS2 device bS■28C.

≦One person. Here, 8 is the projection line shown by the second equation
It is an angle formed with the axis (see FIG. 2), and is a parameter indicating the rotational angular position of the processing electrode 2. Therefore, the 'third'
From the equation, if the flat surface 6 makes an angle of 0 with the The distance on the Y axis between the point (see Figure 2) and the rotation axis 7 is expressed by the formula 1
When the value is , the flat surface 6 comes into contact with the desired elliptical contour surface following the machining plan line shown by the two-dot chain line in FIG. Therefore, the rotational movement of the machining electrode and the Y of the workpiece are maintained so as to maintain the relationship shown in equation (3).
If electrical discharge machining is performed while performing linear movement along the axis, the workpiece can be formed into the desired elliptical contour shape shown by the two-dot chain line. As can be seen from the above description, in the case of a circular shape, the coefficients a and b are equal, so by setting a=b, the same explanation can be applied to the case of circular machining.

FIG. 3 shows a block diagram of a control device 10 for moving the workpiece in the Y-axis direction and rotating the machining electrode according to the relationship of the above-mentioned glue equation. .

The control device 1 outputs an angle signal S corresponding to the above-mentioned angle.
It has an angle detector 11 that outputs an angle signal S, which is input to an arithmetic circuit 12, and according to the following equation,
A target Y-axis position signal S2 indicating a value of 1 corresponding to the angle saw is output. This target Y-axis position signal S2 is applied to the other input of the error detector 14, to which the actual Y-axis position signal S3 from the position detector 13 is input. The actual Y-axis position signal S3 indicates at what position on the Y-axis, which is the movement axis, the point ○ corresponding to the origin position of the coordinate system determined as described above with respect to the machining schedule line on the workpiece 1. This is a signal indicating whether the processing table is located, and is output as a signal corresponding to the position on the Y-axis of the X-Y coordinate system given to the processing table. That is, the origin of the x-y coordinate system given to the processing table is the position of the rotation axis of the processing electrode, and is not the zero point. On the other hand, the target Y-axis position signal S2 is ○ along the Y-axis of the ×-Y coordinate system given to the processing table.
It is a signal corresponding to the distance between a point and the rotation axis, and the error detector 14 detects the difference between rain signals S2 and S3 as an error signal S.
4 and is input to a drive circuit 15 that drives the motor 4. The drive circuit 15 generates a drive pulse signal P for driving the motor 4 so that the value of the error signal S4 becomes zero, in other words, so that the actual Y-axis signal S3 matches the target Y-axis signal S2. As a result, the workpiece 1 is positioned in accordance with the target Y-axis position signal S2 from the arithmetic circuit 12. According to such a configuration, when the machining electrode 2 starts to be rotated from a predetermined initial position, the position of the ○ point on the workpiece 1 changes to the rotation angle position 81.
3}, electric discharge machining is performed between the workpiece 1 and the flat surface 6 of the machining electrode 2 while positioning servo in the Y-axis direction is performed.

Thereby, electrical discharge machining can be performed so that the cross-sectional contour shape of the workpiece 1 becomes a desired ellipse or circle. As can be seen from the Lake equation, if the contour shape of the workpiece 1 is made into a perfect ellipse or circle through continuous machining, the value of 1 must be set to infinity at 8=900 and 2700. In order to avoid this situation, for example, the machined surface may be divided into four quadrants, and the method of the present invention may be applied to each quadrant to obtain a perfect circular or elliptical cross-sectional profile. As can be understood from the above description, the present invention can also be applied to the case where the cross-sectional profile of a workpiece is processed into a partial shape of a circle or an ellipse. Further, the control device shown in FIG. 3 is only one embodiment for implementing the method of the present invention, and by creating an appropriate program for the NC device, the above-mentioned control device between the workpiece and the processing electrode can be controlled. Of course, it is also possible to carry out the method of the present invention by performing a linked movement. In this way, Figure 2,
If the outline of the workpiece is subjected to electrical discharge machining into a circular or elliptical shape or a partial shape as shown in FIG. Since it faces the machining surface, a new electrode surface is always supplied to the electrical machining gap.

Therefore, by causing the workpiece and the machining electrode to perform predetermined movements, extremely accurate machining can be performed without considering electrode wear. Further, the movement of the processing electrode and the workpiece is extremely simple (linear movement and axis rotation movement), and therefore a circular or elliptical shape can be obtained without using a complicated and expensive NC device. In the above embodiment, the case where the discharge surface of the machining electrode 2 is made flat has been explained, but the present invention is not limited to the case where the discharge surface is flat, and depending on requirements, the discharge surface of the machining electrode 2 may be made flat. like,
The discharge surface 6' may have a concave shape with unevenness along the direction of the rotation axis. According to the present invention, as described above, a cross-sectional contour shape including all or part of a circle or an ellipse can be obtained by causing the workpiece and the processing electrode to move along extremely simple movement trajectories. Moreover, it is possible to provide an excellent electric discharge machining method that can perform machining with high precision and high speed.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing an example of a desired elliptical contour shape of a workpiece, FIG. 2 is a schematic view showing the main parts of an apparatus for carrying out the method of the present invention, and FIG. FIG. 4 is a block diagram of the control device of the apparatus, and is a perspective view showing an example of another processing electrode used in the method of the present invention. 1... Workpiece, 2... Machining electrode, 4...
...Pulse motor, 6...Flat surface, 7.
...rotation axis, 8... ...Pulse motor, 10
...Control device, S, . ．． 、． ．． ．． Angle signal, S
2...Target Y-axis position signal, S3...Actual Y-axis position signal, S4...Error signal, P. ...
...Drive pulse signal. Figure 1 Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] 1 The cross-sectional contour shape of the workpiece is ax^2+by^2=r
In the electrical discharge machining method for electrical discharge machining into at least part of a circular or elliptical shape according to A machining electrode whose discharge surface has a straight cross section in a plane perpendicular to the rotation axis is rotated about the rotation axis and at the same time along a predetermined movement axis in a plane perpendicular to the rotation axis. The distance l between the center of the target shape to be machined on the workpiece and the rotation axis is the angle θ between the discharge surface and a straight line perpendicular to the movement axis, and l=±. √(acos^2θ+bsin^2θ)/√
An electric discharge machining method characterized in that electric discharge machining is performed in the machining gap while moving so as to maintain the relationship (ab)·r/(cos θ).