Process Analysis of Plastic Parts (PC / ABS) with a shrinkage of 0.5%. Its external dimensions are Φ 20 × 16 mm and the average thickness is 2.5 mm. It is a kind of polycarbonate / acrylonitrile-butadiene-styrene copolymer. The internal structure of the plastic parts more complex, both the ribs, but also with the structure of the assembly, requiring good electrical insulation properties, with a certain mechanical strength, abrasion resistance, flame resistance and dimensional stability. Plastic parts of the outer surface of the structure is simple, from the die molding can be. The internal structure of plastic parts, such as by the overall punch molding, will make the punch structure of the complex to the manufacturing difficulties, while the plastic parts is not easy to mold, so consider the post-mold insert and inlay molding plastic parts for internal assembly structure. At the same time, because after the molding of plastic molding parts on the back side of the larger holding force, using a mold easy to damage the plastic parts, so consider the second release structure.
The knob is a hand-operated, manual-operated component. According to the functional requirements are divided into continuous rotation, the rotation angle can reach 360 °; also do positioning rotation. Classification of its shape can be divided into circular knob, multi-knob, pointer knob, manual turntable and so on.