Research on the algorithm of tool interference pro

Research on the algorithm of tool interference processing in NC turning

in the NC automatic programming system, the interference processing of tool angle exists in the automatic generation of tool path. Aiming at the tool angle interference in NC turning, this paper puts forward an algorithm for the company to announce that its graphene based supercapacitor samples have been successfully offline. The practical application shows that the effect is good

1 pretreatment of part drawing before tool interference processing

according to the characteristics of parts processed by NC turning, parts can be divided into: outer (inner) surface, chamfer, undercut and thread. Due to the characteristics of turning, the undercut and thread are first replaced by the outer surface in the tool interference processing, so the tool interference processing during part processing only needs to consider the tool interference during surface processing

2 tool interference processing algorithm

by preprocessing the part drawing before interference, at this time, the contour of the machined part is composed of straight lines and arcs, so the tool interference processing in NC turning is only the interference processing in straight lines and arcs

in order to reduce the installation error caused by multiple installation, one-time clamping is generally used in NC machining. For those parts that need to be turned around, the right deviation tool reverse cutting is adopted. The tool interference processing algorithm for reverse cutting is similar to that for forward cutting. In addition, the algorithm of tool interference processing in inner surface machining is also similar to that in outer surface machining. Therefore, this paper intends to discuss the algorithm of tool interference processing when cutting the outer surface forward

as shown in Figure 1, if the part contour is a straight line, it is represented by a directed line segment; if it is a quadrant arc, it is decomposed. The tool is a left offset tool, and the included angle between the cutting edge of the tool pair and the Z coordinate axis is α,β It is the included angle between the part contour line and the Z coordinate axis, as shown in Figure 2

Figure 1 Figure 2

1) tool interference processing algorithm when cutting straight lines

as shown in Figure 2, when β ≤ α There is no interference during cutting

when β> Can be stretched infinitely α As shown in line C in Figure 2, when the tool is processed here, it will leave the residual part of the shadow in the figure. In order to cut out the residual part, it can be cut by changing the tool angle or by reverse cutting. In order to reduce the number of tool replacement and unify the algorithm of tool interference processing, this algorithm adopts the method of reverse tool walking to cut off the residual part. As shown in Figure 2, convert its segment C into an angle of α For the residual part, the right offset cutter is used for cutting in the next step. The cutting starting point is located at point Q in the figure. The tool path is QDC and C is the end point. The outline shape of the part drawing can be machined through forward and reverse cutting

2) tool interference processing algorithm when cutting an arc

when the part contour is the first quadrant arc, the tool cuts the arc without interference

when the part contour is the second quadrant arc, tool interference may occur during cutting with the different positions of the starting point and end point of the part contour arc. As shown in Figure 3 (a), the angle is α The line L of is tangent to the arc C, and its tangent point is t. when the starting point of the arc to be cut is located to the left of the tangent point t, there is interference. The arc C is decomposed into arcs C 'and C'. When cutting C ', there will be no interference, but when cutting C ", there will be interference. Therefore, the arc C" will be replaced by its tangent TP, and the auxiliary line PD (PD is the vertical line that intersects the tangent through the end point of the arc in this section) will be added. The purpose of adding this auxiliary line is to facilitate the implementation of the algorithm. In the subsequent processing, for this section, 5. The processing after the arc is replaced by the tangent before the start-up of the rubber planer is the same as the above processing of the straight line. Similarly, the processing of the auxiliary line is also transformed into the above processing of the straight line

(a) (b) (c)

Figure 3

when the part contour is the third quadrant, the cutting tool does not interfere during cutting

when the part contour is in the fourth quadrant, the cutting process may produce serious interference depending on the different tool angles. As shown in Figure 3 (b), the angle of the starting point of the arc is α Find the intersection of the line and the arc. If the intersection exists, the left cutting of the intersection has no interference, while the right cutting has interference. Cut the arc at the intersection and convert the arc on the right to an angle α Line L of. If the intersection is not on the arc, convert the arc into an angle of α At the same time, it passes through the end of the arc as a vertical auxiliary line, as shown in Figure 3 (c). The treatment of the residual part is the same as above, and it is cut off by reverse cutting

3 algorithm implementation

according to the above algorithm principle, through the analysis of the characteristics of the part drawing, the processing of tool interference in the program design of the algorithm implementation can be divided into the following three cases:

· straight line is connected with straight line

· the straight line is connected with the arc

· arc

1) processing of connecting straight lines. If there is tool interference when cutting a straight line, as shown in Figure 4 (a), use the angle of the straight line as α At the same time, the intersection of this line and the subsequent lines is calculated. If there is an intersection, the line is truncated at the intersection, and the right part of the line at the intersection is converted into an angle of α If there is no intersection or the intersection is not on the line, the next line is also converted to an angle α The Z coordinate of its end point is the Z coordinate of the line segment, and a vertical auxiliary line is added, as shown in Figure 4 (b)

2) when the straight line is connected with the arc in the first quadrant, there is no interference when the tool cuts the arc, but if there is interference in the cutting straight line, convert the straight line into an angle of α The straight line L of is shown in Figure 5 (a). Then the starting point of the arc is modified to the intersection of the line L and the arc. If there is no intersection, it indicates that the arc is under the line. At this time, the arc is also converted into an angle of α The Z coordinate of the end point of the straight line is the Z coordinate of the end point of the arc. As shown in Figure 5 (b) (considering the structural manufacturability, this structure should be avoided in design)

3) when the straight line is connected with the arc in the second quadrant, the cutting straight line and arc of the tool may interfere at this time. If there is interference in the cutting line of the tool, its excellent toughness helps to ensure that the rib parts of the water inlet (outlet) fasteners of the polimotor 2 can maintain a reliable seal without cracking. The processing algorithm is the same as that described in Section 1 of this paragraph. If the subsequent arc connected with the straight line also has tool interference, convert the arc into an angle of α The processing algorithm of the straight line is the same as that described in Section 2 of this paragraph

4) when the straight line is connected with the arc in the third quadrant, the tool has no interference when cutting the arc, but if the cutting straight line has interference, its processing algorithm is the same as that described in Section 2 of this paragraph

5) when the straight line connects with the fourth quadrant arc, the cutting straight line of the tool may interfere at this time. Cutting arcs may also interfere. If there is interference in the processing of the straight line, the processing algorithm is the same as that of cutting the straight line. The algorithm of interference processing in arc cutting is the same as the above algorithm of arc cutting

6) algorithm block diagram

figure 6

4 conclusion

1) this algorithm is stable and reliable. An automatic programming system that can be applied to NC turning

2) according to the algorithm described in this paper, when machining parts of some shapes, it can be completed only after repeated forward and reverse cutting if necessary. However, since the cutting process generally includes rough machining and finishing, the small residual of under cutting caused by the tool angle can be temporarily ignored and treated in finishing or semi finishing. Due to the improvement of cutting conditions, the probability of tool interference is much smaller in finishing machining

3) during reverse cutting, interference may occur at the starting point of the tool. At this time, interference due to the large size of the tool head should be considered

4) the algorithm discussed in this paper has nothing to do with the shape of the blank contour, and is suitable for all kinds of blank shapes. (end)