In the manufacturing industry, plastic materials are widely used to achieve flame retardant, insulation, wear resistance such kind of characteristics.
As in the process of CNC machining, heat will be generated anyway, that would put affect on the characteristic of plastics. In order to get qualified machined plastic parts, the first important is to use semi-finished products treated with internal stresses, the heat generated during machining process will lead to the release of internal stress, which resulting in deformation parts. For materials with high water absorption (such as nylon), dehumidification is needed before processing. The tolerance of plastic is bigger than metal, also plastic thermal expansion coefficient is much larger than the metal. So when machining plastics, these two factors must be take into account.
As plastic material such as Nylon, PC, PMMA, ABS etc has a smooth surface already. But the surface will be damaged after machining, therefore, whenever possible, try to retain the original material surface during machining. Plastic parts still need extra surface treatment after machining.