JPS6010854B2 - Wire cut electric discharge machining method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a novel method for performing contour machining with high precision using a wire-cut electrical discharge machining device.

As shown in FIG. 1, this type of wire-cut electrical discharge machining apparatus normally has a machining fluid supply device 3 in a machining gap where a wire electrode 1 and a workpiece 2 face each other on the 0.05 to 0.3 side.
Electric discharge is repeatedly performed by the machining power source 5 using the machining fluid 4 supplied from the machining fluid 4 as a medium.

The movement of the processing portion 6 is performed by a drive motor 8 that operates an It is something that The drawbacks of the conventional wire-cut electrical discharge machining method are shown in FIGS. 2 and 3.

In FIG. 2, when the wire electrode 1 advances from A to C to E in the figure and processes a right-angled corner of the workpiece 2, it is known that "sagging" as in the right-angled corner portion 10 occurs. ing. The reason for this is that since the wire electrode 1 is a non-rigid body, it bends due to the anti-trailing force of the discharge, and the actual wire path moves from A to B to D to E, so the right-angled corner part 10 is redundantly machined. It will be done. Further, until the wire electrode 1 passes the right-angled corner portion 10, the right-angled corner portion 10 is unnecessarily machined because vibration is free in the A direction. These causes the right angle corner portion 10' to sag. Next, as shown in FIG. 3, when the wire electrode 1 advances in the direction of the arrow in the figure, the machined surface 12 exhibits unevenness with respect to the contour line 11, which ultimately leads to fluctuations in the machined groove width and dimensional accuracy. This results in the drop of . In addition, in the case of wire cut electric discharge machining, in addition to the inherent surface roughness depending on the power supply conditions, the machined surface 12 as described above
Waviness occurs due to the unevenness of the surface. This ultimately leads to a poor final tax. In addition to the vibration of the wire electrode 1, the causes of unevenness on the machined surface 12 include non-uniform removal of machining powder, stable/unstable electric discharge, and the like. In order to solve these problems even if only a little, we have conventionally adopted a method of reducing the discharge energy, suppressing the vibration of the wire electrode 1, suppressing the generation of machining powder, and suppressing the machining speed to allow the discharge to proceed stably. It is known that However, if precision machining is always performed with this method, it is necessary to sacrifice machining speed, which is not preferable.
However, under such circumstances, it becomes necessary to improve the surface-to-surface machining speed as well as the dimensional accuracy and shape accuracy. Therefore, the present invention has focused on the fact that the above-mentioned drawbacks are caused by vibration of the wire electrode, poor removal of processed powder, etc., and established a new processing method to eliminate the above-mentioned drawbacks. In FIG. 4, in the first machining, the right-angled corner 10' has a "sag".

However, as shown in the figure, by reducing the second machining allowance 13, the "sag" can be eliminated. The reason for this is that the second machining allowance 13 is very small (usually 5 to 10 mm), so the reversal force of the discharge is also much smaller than that of the first machining, and the wire electrode deflection is also much smaller. becomes smaller,
The wire electrode moves in the direction of the arrow shown by the dashed line in the figure, and the "sag" at the right-angled corner portion 10 is eliminated. As a matter of course, the wire electrode vibration is suppressed to a much greater extent than that in the first machining process, so that a right-angled corner portion 10 with an appropriately correct contour line 11 can be obtained. However, the relative movement between the wire electrode 1 and the workpiece 2 is defined by, for example, a program. Next, in FIG. 5, the first processed surface 12 has undulations, but if the second processing is performed as shown in the figure, the second processed surface will be formed according to the contour line 11.

The reason for this is that, in addition to the explanation in Fig. 4, the discharge is performed only on one side of the wire electrode 1 in the figure, and the removal state of the machining powder is uniform in the direction perpendicular to the plane of the drawing. This is because the state can be repeated in a stable manner. As a result, as shown in FIGS. 4 and 5, very accurate machining can be performed, but in order to perform the second machining, a machining starting point is always required.

Therefore, depending on where the machining start point is set, it depends on whether or not the accuracy can be improved by performing the second machining. The above content will be discussed below.
As shown in FIG. 6, if the die side is required, for example in the case of punch and die processing, a small hole 14 is opened and the wire electrode 1 is passed through the run-up section 15 for a certain distance. Processing is performed in the direction of the middle arrow to form the contour line 11, and the process ends again at section F. As a result, as shown by the downward arrow, a protrusion 16 is formed with an arc equal to the sum of the radius of the wire electrode 1 and the discharge gap on both sides.
It is generally known that this always occurs after being cut into parts.

Therefore, as shown in FIG. 7, if the second machining is started from a position where electrical discharge occurs with the protrusion 16, the workpiece 2 on the die side is combed against the contour line 11 as shown on the right side of the figure.
It gets confusing. This is because when the wire electrode 1 approaches the protrusion 16, since the protrusion 16 is sharp, discharge first occurs between the wire electrode 1 and the protrusion 16, and ionization progresses in the vicinity, making it extremely easy for discharge to occur. 1 other than protrusion 16
Electric discharge occurs even from a position far from the second machined surface. As a result, the electrical discharge continues to occur with the machined surface 12 until the wire electrode 1 finishes bending, resulting in excessive electrical discharge with respect to the contour line 11 in the figure. In this case, as mentioned above, machining is performed twice to improve accuracy.
Even if it is repeated, the value of the product will be lost if it has the biggest drawback of being combed into the die side at the start of the second processing. Therefore, the present invention is carried out as follows in order to eliminate the above-mentioned drawbacks. In other words, as shown in FIG. 8, machining is started from a position where the wire electrode 1 does not cause electrical discharge with the protrusion 16. In this case, since insulation is maintained between the wire electrode 1 and the machined surface 12, when the distance of the regular discharge gap is reached (in the figure, the broken line circle surrounding the wire electrode 1 and the machined surface 12 are connected for the first time). Discharge occurs for the first time at a distance between the two, and the wire electrode 1 advances to the position P in the figure and bends in the direction of the arrow, so excessive discharge as shown in Figure 7 can be prevented, and the machined surface 12 has a contour. line 11
It will be processed up to the point. Furthermore, as stated in claim 2, when the wire electrode 1 is processed to the position Q in the figure, the protrusion 16 can also be removed along the contour line 11. If the wire electrode 1 is moved from Q to P while machining, the protrusion 17 caused by the second machining can also be removed, completing machining of 11 contour lines, and improving machining accuracy as described above. It can be measured. Finally, when performing the second machining, the number of machining speeds of the first time is 1M sound speed (2
Because the machining allowance for the second machining is minute), it is possible to avoid sacrificing machining speed, which is the disadvantage of conventional methods.
Improvements in surface roughness, dimensional accuracy, and shape accuracy can be expected. Note that it is better to reduce the discharge energy in the second and subsequent machining to further reduce the machining allowance, which results in a more negative layer effect. In summary, in order to improve surface roughness, dimensional accuracy, and shape accuracy in areas where machining speed is high, the present invention performs machining two or more times along the first machining surface, and then performs machining two or more times. A new problem that arises is that by changing the starting position of machining, machining is completed twice or more. The effects of its implementation are extremely large.

[Brief explanation of the drawing]

Fig. 1 is a system diagram of a wire-cut electrical discharge machining device, Figs. 2 and 3 show the drawbacks of conventional machining, Figs. 4 and 5 show the advantages of the present invention, and Fig. 6 shows the protrusion generation process. , FIG. 7 shows the drawbacks of the present invention, and FIG. 8 shows a countermeasure for the problem shown in FIG. 7, and also uses an explanatory diagram of claim 2. Note that the same symbols in the figures represent the same parts. 1...
Wire electrode, 2... Workpiece, 10...
・Right angle corner, 11... Contour line, 13... Machining allowance, 1
6...Protrusion, 17...Protrusion due to second processing. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8

Claims (1)

[Scope of Claims] 1. In a method of cutting the workpiece into a closed curve by relatively moving a wire electrode and the workpiece, After removing the workpiece, the wire electrode and the workpiece are moved relative to each other, with a position different from the position of the protrusion left on the workpiece due to the first cutting as a position to start the second actual electrical discharge machining. A wire cut electric discharge machining method characterized by moving the workpiece and further machining the machined portion of the workpiece along its machined surface. 2. The wire cut electric discharge machining method according to claim 1, wherein when the machined portion of the workpiece is further machined along its machined surface, the protrusions of the workpiece are also machined.