Programming Parameters for Custom Router Bits and Plastics
When working with plastics, the custom router bits that you use will dramatically affect the finish of the cut edge. Even the most perfectly chosen custom router bits will not be able to provide the perfect finish without having to go over it again if you have not programmed the cutting parameters and cutting methods correctly, though. During the plastic machining process, you will find that there is an optimal place where the material and cutting tools meet their perfect match of cutting parameters.
Even the slightest deviation in the plastic machining direction can lead to a much poorer finish on the cut edge of the material, whether it is hard or soft plastic. The most common variables that you will consider in the plastic machining process are the feed and speed. These are the most sensitive areas when it comes to variation. Unlike metal cutting router bits and upcut wood router bits, plastics require bits that are programmed to an extremely narrow chip load range to produce an optimal finish with no room for error. Assuming that the spindle speed is kept at 18,000RPM and the depth of cut is equal to the cutter diameter, the optimum chip load for 1/8" Diameter custom router bits is 75-100 IPM, and for 3/8" bits it’s 125 to 250 IPM.
The feed rates on custom router bits for plastics can be increased by simply increasing the spindle RPM, as long as the tools are not experiencing any stability problems and the work piece is well fixtured. Unlike metal cutting router bits and upcut wood router bits, though, increased spindle speeds must be accompanied by an increase in feed rate to remain within that ideal spot on the chip load. When the spindle speeds are too disproportionately high, that common problem of the plastic chips melting and re-welding to the surface can occur, or it might also result in a wiping or smearing action on the finished edge. Either way, the surface finish is not what you were looking for.
Programming the feeds and speeds, as well as other parameters such as cutting method, make all the difference in the finished product.