We all know that a reasonable choice of processing route can not only improve the cutting efficiency, but also improve the surface machining accuracy of the part. The feed route of the tool on the CNC machining center can be divided into the hole machining feed route and the milling machining feed route. The milling machining feed route is the problem of milling machining tool trajectory generation. The following mainly introduces the hole machining feed route.
During hole machining, the tool is generally positioned and moved to the position of the hole centerline quickly in the XY plane, and then the tool is moved in the Z direction (axial direction) for machining. Therefore, the determination of the hole feed route includes:
1. Determine the feed route in the XY plane
During hole machining, the motion of the tool in the XY plane belongs to point motion. When determining the feed route, the main considerations are:
(1) Positioning should be rapid
That is, the empty travel time is as short as possible without the tool colliding with the workpiece, fixture and CNC machining center machine tool. For example, machining the parts shown in Figure 5-34a. Feeding according to the feed route shown in Figure 5-34b saves positioning time by nearly half compared to feeding according to the feed route shown in Figure 5-34c. This is because in the case of point movement, when the tool moves from one point to another, it usually moves quickly along the X and Y coordinate axes. When the X and Y axes move differently, the movement in the short travel direction first Stop, the tool will not reach the target position until the movement in the long travel direction stops. The scheme in Fig. 5-34b makes the distance along the two axes close, so the positioning process is rapid.
(2) Positioning should be accurate
When arranging the feed route, it is necessary to avoid the effect of the mechanical feed system backlash on the hole position accuracy. For example, boring 4 holes in the part shown in Figure 5-35a. According to the feed route shown in Figure 5-35b, because the positioning direction of 4 holes is opposite to that of 1, 2, and 3 holes, the Y-direction backlash will increase the positioning error, which will affect the position accuracy of 4 holes and other holes. According to the feed route shown in Figure 5-35e, after processing 3 holes, move up a distance to point P, and then fold back to position processing at 4 holes, so the direction is consistent, you can avoid the introduction of reverse gap , Improve the positioning accuracy of 4 holes.
Rapid positioning and accurate positioning are sometimes difficult to meet at the same time. In the above two examples, Figure 5-34b is based on the shortest route, but it does not approach the target position from the same direction, which affects the positioning accuracy of the tool. Figure 5-35c is Approaching the target position from the same direction, but not the shortest route, increases the empty stroke of the tool. At this time, the main contradiction should be grasped. If feeding according to the shortest route can ensure the positioning accuracy, then the shortest route should be taken;