A new method of turning processing in the most pop

A new method of turning processing in multi axis linkage NC machining

in multi axis linkage NC machining, the machining surface is formed by the envelope of the tool cutting along a continuous tool path. Therefore, the generation technology of tool path is one of the key technologies in CAM system. How to make the length of tool path shortest, arrangement more reasonable and processing easier is an important topic of pre oral NC machining research. In the continuous cutting process, the piston 5 moves upward from the end of the previous track to loosen the sample 7 By adjusting the overflow valve point on the oil source to the starting point of the next track, steering processing is required, as shown in Figure 1. Whether the turning is handled properly is directly related to the machining efficiency, machining accuracy and the difficulty of machining. However, in the surface processing of large parts, the amount of steering track accounts for a small proportion in the total track length, so steering processing is often not paid much attention, resulting in some NC software wasting a lot of machine time because of the unreasonable steering processing method

in multi axis NC machining, both ball head tools and flat bottom tools can be used. Because the normal vector of the ball head cutter is self-adaptive, the turning processing method is cumbersome. The rotation angle of the cutter shaft is large when turning, and because the curved surface boundary has not been cut out, the boundary cutting problem must also be considered when turning. Therefore, this paper proposes a simple and efficient boundary turning algorithm

1 methods to avoid boundary cutting

first, introduce the methods to avoid boundary cutting. As shown in Figure 1, some literatures regard the cutting contact m of the tool cutting out of the theoretical surface as the cutting termination criterion of a single track. At this time, the boundary has not been completely cut out, so it is necessary to cut out the unmachined boundary when turning. The author adopts a different method from the literature, taking the ideal surface cut out of the left and right cutting width points P1 and P2 as the ending cutting condition of a single track, so as to ensure that the boundary can be completely cut out in one cutting. At the same time, if the starting point of the next trajectory line is inside the boundary of the ideal surface, a tool position should be interpolated in the opposite direction of its feeding direction, so that the interpolated tool position is located on the boundary of the surface, so as to ensure that the boundary can be completely cut out during the next tool walk

Fig. 1 Schematic diagram of the end cutting of a single track

2 steering processing process

as shown in Fig. 2, the specific process of steering processing is: starting from the end point of the previous track, that is, turning after cutting out the effective width, interpolating several tool centers in a straight line between the end tool point of the previous track and the start tool point of the next track, and interpolating the same number of tool axis vectors in the acute angle direction Q between the two tool axis vectors AC and a'c, As the turning tool position value, in actual processing, the tool is driven according to this tool position value. In the process of steering, it is unnecessary to care about the attitude of the cutter shaft and the cutting condition of the boundary, and it is not necessary to detect the height of the residual area, but only to detect and correct the interference

Figure 2 steering process

3 interference correction in steering processing

the magnitude of interference D can be obtained by the residual area detection method introduced in other literature. First, calculate the distance t from each point on the tool tip trajectory circle (Fig. 1) of the flat bottom tool to the theoretical surface. When t 0, it indicates that there is no overcut interference; When t 0, it means that the tool tip cuts the surface at this point, that is, overcut interference occurs. Finally, the maximum interference D is obtained by comparing the size of each interference point t|. The interference correction can directly adopt the method of lifting the tool, as shown in Figure 3, that is, under the condition of keeping the tool axis vector unchanged, raise the tool along the axis by a distance d'

d'=d/cosb (1)

, where: D is the maximum interference; B is the angle between the unit normal vector n at the maximum interference point and the unit vector AC of the cutter axis, that is, b=cos-1 (n AC)

the tool axis vector of the corrected tool location remains unchanged, and the tool center vector is

r'c=rcd'ac (2)

, where: RC is the tool center vector before correction

figure gem: only when it shines can it stand out. 3. Interference treatment in steering process

4 conclusion

in NC cutting, the milling cutter should be gradually introduced into the actual hydraulic universal experimental machine. When we work, we must understand the focus of our test this time and should avoid the cutting position of those technical defects. The starting point is outside the surface. After cutting, the milling cutter should go out of the surface along the feed direction and stop outside the surface. When cutting to the boundary, ensure that the boundary surface is completely cut out. The turning treatment method introduced in this paper meets the above requirements well, is simple and easy, and greatly improves the efficiency of boundary cutting. (end)