Application of taper machining and programming tec

2022-07-31
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Example application of NC wire cutting taper machining and programming technology

NC wire cutting machine has solved many problems that are difficult to be solved by traditional machining, especially in the processing of products with acute angle, small R and taper cutting. It has been widely used in mechanical mold, aerospace, aerospace and other industrial fields. The accuracy of the draft surface of the punch and die has an important impact on the mold opening and service life. Therefore, the taper machining of the draft angle is particularly important

I. key points of machining large and thick workpieces and taper cutting

machining large and thick workpieces and taper products has always been the key processing object and one of the difficulties of wire cutting. Improving the vertical accuracy and processing efficiency of large and thick workpieces has always been one of the goals of wire cutting. The cutting of large and thick workpieces often presents concave and arch shapes as shown in Figure 1. The causes of arch or concave die shape are generally caused by the low resistance ratio of the processing fluid, the too small tension of the cutting wire, the too large distance between the guides and so on. In case of concave shape, it can be solved by reducing the average machining voltage (servo reference voltage) during secondary cutting, while in case of arch shape, it is necessary to increase the average machining voltage during secondary cutting

1. Key points for machining large and thick workpieces

when machining large and thick workpieces, the perpendicularity and cutting accuracy of large and thick workpieces can be improved by the following means

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

(2) use cutting wire with larger diameter for processing, and increase the processing times

(3) special nozzle is used to improve the cooling effect of cutting fluid

2. Taper indication error is an inevitable machining point of taper cutting

for taper cutting, its size is often difficult to control, and the cutting efficiency is much lower than that of non taper cutting, especially in the case of large taper. This is mainly caused by many reasons, such as difficult chip removal during taper machining, unsatisfactory cutting fluid environment and unreasonable electrical parameters. The following are some machining points summarized by the author according to the specific situation of taper cutting in practice

(1) due to the difficulty in chip removal during taper cutting, the cutting wire at the guide head of the wire guide die has a large pulling force and is easy to break, so it is necessary to reduce the processing energy, increase the discharge interval and increase the average voltage during the processing

(2) improve the jet flow, use special nozzles, increase the jet flow with the large opening upward, and use the closed machining method to reduce the z-axis height and minimize the distance between the two nozzles

(3) in the process of taper machining, the machining perimeter on each section layer is different, and the discharge gap is also different. Therefore, more cutting amount should be used in finishing machining than in non taper machining

(4) due to the rigidity of the cutting wire itself, the inclination between the upper and lower guide wire die guides and the cutting wire will produce errors. After changing the hard wire and the production capacity of small and micro enterprises to process more than 80million tons of soft wire, the error caused by the rigidity of the cutting wire can be reduced

(5) since the NC program compensation of WEDM is carried out in the XY plane, the compensation amount will produce errors with the actual compensation value for taper machining, as shown in Figure 1C. When the compensation amount of the program is a, when the cone angle is α The actual compensation amount of the taper surface is only ACOs α, The resulting error is 2A (1-cos α)。 Therefore, in large taper cutting, it is also one of the effective measures to improve the cutting accuracy to modify the program compensation company's inclination compensation in these two fields

a) concave model B) arch C) taper compensation

Figure 1 error form generated when cutting large thickness workpiece

II. Example of taper NC machining programming

NC programming of taper cutting can be carried out in a relatively flexible way according to the actual situation

1 . Fixed taper machining programming

for the fixed taper with the same upper and lower shapes, it is only necessary to compile a two-dimensional contour machining program according to the corresponding reference plane, and then use the inherent fixed taper cutting and machining function of the CNC wire cutting system to cut the taper. Figure 2 shows the NC machining and program code of a female 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 programming method for fixed taper cutting

Figure 2 fixed taper machining programming

2 Programming of variable taper cutting machining

in the processing of actual products, we often encounter variable taper cutting machining in which the upper and lower shapes of products are different or the shapes are roughly similar but the taper is different. For this kind of products, the programming method of upper and lower abnormity is often used, that is, the contour of the upper and lower planes of the workpiece is modeled according to the actual product, and then the tool path of four axis linkage taper cutting of CAM software is used for programming. This method produces a large amount of programs. Vigorously develop the new energy automobile industry figure 3 shows the products and their processing procedures under a certain upper circle

Figure 3 variable taper machining programming

3 Fixed taper reversing programming

Figure 4 shows a thin-walled part product. The taper direction of the inner surface and the outer surface of the product is the same. If the fixed taper is adopted, the contour cannot be processed all at once. If the variable taper method of upper and lower abnormity is adopted for programming, the amount of programs will be large. Therefore, the author combines the programming method of fixed taper, and uses the taper reversing method to complete the processing of the inner and outer surfaces in one program at the same time, It not only ensures the product quality, but also improves the processing efficiency

Figure 4 fixed taper reversing programming

III. conclusion

NC wire cutting is a highly practical work, which needs continuous exploration in practice to find the best processing parameters. This paper only discusses the wire cutting machining strategy for large and thick workpieces and taper products, and focuses on some machining points of taper wire cutting machining, which may be missed. Readers are welcome to discuss

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