Copy milling or contour cutting?

In cavity milling, the best way to ensure the success of down-milling tool paths is to use contour milling paths. Milling cutters (such as ball end mills, see mold manufacturing catalogue C-1102:1). Milling of the outer circle along the contour lines often results in high productivity. This is because on the larger tool diameter, there are more teeth in the cutting . If the speed of the machine spindle is restricted, contour milling will help maintain cutting speed and feed rate. With this tool path, the workload and direction changes are also small. This is particularly important in high-speed milling applications and hardened materials processing. This is because if the cutting speed and feed rate are high, the cutting edge and the cutting process are more susceptible to the adverse effects of changes in the working load and direction. Changes in the working load and direction will cause changes in the cutting force and tool bending. Copy milling along steep walls should be avoided as much as possible. When profile milling, the chip thickness at low cutting speed is large. In the center of the ball-end knife, there is a danger of the cutting edge chipping. If the control is poor, or the machine tool has no pre-reading function, it will not be able to decelerate fast enough, and the risk of edge chipping will most likely occur in the center. The upper profile milling along the steep wall is better for the cutting process, because the chip thickness is at its maximum value at a favorable chip speed.

In order to get the longest tool life, the cutting edge should be kept continuous cutting for as long as possible during the milling process. If the tool enters and exits too frequently, the tool life will be significantly shortened. This will increase the thermal stress and thermal fatigue on the cutting edge. A uniform and high temperature in the cutting area is more beneficial to modern cemented carbide tools than a large fluctuation. The profiling milling path is often a mixture of up-milling and down-milling (zigzag), which means that the tool will be frequently eaten and retracted during cutting. This kind of tool path also has a bad influence on mold quality. Every time you eat a knife, it means that the knife is bent, and there is a lift mark on the surface. When the tool is withdrawn, the cutting force and the bending of the tool are reduced, and there will be a slight overcutting of material in the exiting part.