Profile milling or contour cutting?
In cavity milling, the best way to ensure the success of tool path is contour milling. Milling cutters (e.g. ball end milling cutters, see mould manufacturing sample C-1102:1) Cylindrical milling along contour lines often yields high productivity, because more teeth are being cut in larger tool diameters. If the spindle speed of machine tool is limited, contour milling will help to maintain cutting speed and feed rate. With this tool path, the change of workload and direction is also small. This is particularly important in the application of high-speed milling and the processing of hardened materials. This is because if the cutting speed and feed are high, the cutting edge and cutting process will be more vulnerable to adverse effects of changes in workload and direction, and changes in workload and direction will cause changes in cutting force and tool bending. Profile milling along steep walls should be avoided as far as possible. When profile milling is carried out, the chip thickness is large at low cutting speed. In the center of the ball-nose knife, there is also the danger of the edge breaking down. If the control is poor or the machine tool has no pre-reading function, it can not decelerate quickly enough, which is most likely to cause the risk of edge collapse in the center. Upper profile milling along the steep wall is better for the cutting process, because the chip thickness is the maximum at favorable chip speed.
In order to obtain the longest tool life, the cutting edge should be kept continuous cutting for as long as possible in the milling process. If the tool enters and exits too frequently, the tool life will be significantly shortened. This will aggravate the thermal stress and fatigue on the cutting edge. It is more advantageous for modern cemented carbide tools to have uniform and high temperature in the cutting area than to have large fluctuations. Profile milling paths are often a mixture of reverse milling and forward milling (zigzag), which means that knives are frequently eaten and retracted in cutting. This kind of tool path also has a bad effect on the quality of the die. Every time a knife is eaten, it means that the knife is bent, and there is a mark of lifting on the surface. When the tool exits, the cutting force and the bending of the tool decrease, and there will be slight material "over cutting" in the exit part.