In the process of CNC machine tool processing, the tool moves from the starting point or the tool change point to the position close to the workpiece to improve the processing efficiency. It returns to the starting point or the tool change point in G00 (rapid point positioning) mode. The principle of considering the retract path is: first, to ensure safety, that is, not to collide with the workpiece during the retracting process; second, to consider the shortest retract path, shorten the idle stroke, and improve production efficiency.
According to the different parts of the tool processed by the tool, the determination of the retract path is also different. The following three retreat routes are commonly used in CNC lathes:
The oblique tool retraction route (as shown in Figure 1) has the shortest stroke, suitable for the offset tool retraction of the outer circular surface.
The radial and axial retract path means that the tool first retracts vertically in the radial direction and then retracts axially when it reaches the specified position. The grooving shown in Figure 2 adopts this kind of retreat route.
The order of the axial and radial retreat routes is exactly the opposite of the radial and axial retreat routes. The boring process shown in Figure 3 adopts this kind of tool retreat route.
Setting the tool change point of the CNC lathe tool is a problem that must be considered in programming the machining program. The safest position of the tool change point is where any tool on the tool post or cutter head does not collide with the workpiece or other parts of the machine tool during tool change.
Generally, in single-piece and small-batch production, we set the tool change point as a fixed point whose position does not change with the position of the workpiece coordinate system. The axial position of the tool change point is determined by the tool with the longest axial projection on the tool holder (e.g., bore boring tools, drills, etc.); the radial position of the tool change point is determined by the tool with the longest radial projection on the tool holder (e.g., external turning tools, grooving tools, etc.).
In mass production, to improve production efficiency, reduce the idle travel time of the machine tool, and reduce the wear of the machine tool rail surface, sometimes it is not necessary to set a fixed tool change point. Each tool has its tool change position. At this time, the programming and debugging of the tool change part should follow two principles: first, ensure that the tool does not collide with the workpiece during tool change; second, strive for the shortest tool change route, the so-called "follow tool change."