Numerical control wire cutting taper machining and programming technology example application (Figure)

CNC wire-cutting machine tool processing solves many difficult problems that traditional machining is difficult to solve, especially in the processing of sharp angle, small R and taper cutting products, and has been widely used in mechanical mold, aviation, aerospace and other industrial fields. The accuracy of the die face of the convex and concave mold has an important influence on the mold opening and service life of the mold. Therefore, the drafting of the draft angle is particularly important.

First, the processing points of thick workpiece and taper cutting

The processing of thick workpieces and taper products has always been the key processing object of wire cutting, and it is also one of the difficulties. Improving the vertical precision and processing efficiency of thick and thick workpieces has always been one of the goals pursued by wire cutting. Large thick workpiece cuts often exhibit a concave shape and an arch shape as shown in FIG. The reason for the arch or concave shape is generally caused by the fact that the resistance ratio of the working fluid is too low, the tension of the cutting wire is too small, and the distance between the guides is too large. In the case where a concave shape occurs, it can be solved by reducing the average machining voltage ( servo reference voltage ) at the time of secondary cutting , and in the case of an arch shape, the average machining voltage at the time of secondary cutting is increased.

1 . Machining points when cutting thick workpieces

When processing thick and thick workpieces, the verticality and cutting accuracy of thick and thick workpieces can be improved by the following means.

( 1 ) increase the tension of the cutting wire and reduce the distance between the nozzle guides;

( 2 ) processing with a relatively large diameter cutting wire and increasing the number of processing;

( 3 ) Use a special nozzle to improve the cooling effect of the cutting fluid.

2 . Processing points of taper cutting

For taper cutting, the size is often difficult to control, and the cutting efficiency is much lower than that without taper cutting, especially in the case of large taper. This is mainly due to many reasons such as difficulty in chip removal during taper processing, unsatisfactory environment of cutting fluid, and unreasonable electrical parameters. The following are some of the processing points that the author has summarized from practice in the specific situation of taper cutting.

( 1 ) Due to the difficulty in chip removal during taper cutting, the cutting wire of the guide wire of the guide wire has a large drag force and is easy to break, so it is necessary to reduce the processing energy, increase the discharge interval time, and increase the average voltage during the processing;

( 2 ) Improve the jet flow condition, use a special nozzle, increase the jet flow rate with the large opening upward, and reduce the Z- axis height by the closed machining method, and try to minimize the distance between the two nozzles;

( 3 ) Since the machining circumference is different in each section layer during the processing of the taper, the discharge gap is also different, so more cutting amount than the non-tapering processing should be used in finishing;

( 4 ) Due to the rigidity of the cutting wire itself, the inclination of the upper and lower guide wire die guide heads and the cutting wire may cause an error, and the hard wire is processed for the soft wire to reduce the error caused by the rigidity of the cutting wire;

( 5 ) Since the NC program compensation of the wire cutting process is performed in the xy plane, for the taper machining, the compensation amount and the actual compensation value may cause an error, as shown in Fig. 1c . When the compensation amount of the program is A , the actual compensation amount of the taper surface is only Acos α when the cone angle is α, and the resulting error is 2A(1 - cos α ) . Therefore, in the case of large taper cutting, correcting the program compensation is also one of the effective measures to improve the cutting accuracy.

a concave model b arch c taper compensation

Figure 1 shows the error form produced when cutting a large thickness workpiece

Second, taper CNC machining programming examples

The numerical control programming of taper cutting can be carried out in a relatively flexible manner according to the actual situation.

1 . Fixed taper machining programming

For the fixed taper with the same shape of the top and bottom, it is only necessary to prepare a two-dimensional contour machining program according to the corresponding reference reference plane, and then the taper cutting can be performed by using the fixed taper cutting processing function inherent in the CNC wire cutting system. Figure 2 shows the CNC machining and program code for a die part. This method is intuitive, the program is simple, and it is easy to find errors in the program. It is a commonly used fixed taper cutting processing programming method.

Figure 2 fixed taper machining programming

2 . Variable taper cutting programming

In the processing of actual products, it is often encountered in variable taper cutting processes in which the top and bottom shapes of the products are different or the shapes are substantially similar and the taper is not equal. For these products, the upper and lower profile programming method is often adopted, that is, the contour of the upper and lower planes of the workpiece is three-dimensionally shaped according to the actual product, and then the tool path of the four-axis linkage taper cutting of the CAM software is used for programming, which generates a larger program amount. . Figure 3 shows the product underneath the upper circle and its processing.

Figure 3 variable taper machining programming

3 . Fixed taper commutation programming

Figure 4 shows a thin-walled part product. The inner surface and the outer surface of the product have the same taper direction. If a fixed taper is used, the contour can not be processed at one time. If the upper and lower profile variable taper method is used for programming, the program generated is large, and the author combines the fixed taper. The programming method uses the taper reversal method on the inner surface and the outer surface to simultaneously complete the inner and outer surfaces in one program, which improves the processing efficiency while ensuring the product quality.

Figure 4 fixed taper commutation programming

Third, the conclusion

CNC wire cutting is a very practical work that needs to be explored in practice to find the best processing parameters. This paper only discusses the wire cutting processing strategy of thick workpieces and taper products, focusing on some processing points of taper wire cutting processing, which may hang a leak, welcome readers to discuss.

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