When using the ball end mill processing, even if you select the appropriate line speed and depth of cut processing, but there are many factors that lead to a decline tool life.
The load increases at the start of cutting
     The tool in the z-axis direction vertical drop, the beginning of the cutting, the tool center line slow first came into contact with the workpiece, the processing starts, will inevitably become the groove machining. When processing the feed trough has the right and left direction of the workpiece, while declining to become the processing, while the increase in processing. In particular increased machining, tool life, machining surface finish will decline. Therefore, compared with the usual side processing, feed rate must be reduced.
     Using a tool like painting methods as spiral downward spiral machining the workpiece contact, although eliminating the slow line, the tool center piece first contact problem, but can not say that is the best way, that is, after the end of the screw into the straight line when processed, or grooving. Here, if the feed rate does not drop, but also lead to shorter tool life reasons.