Last, but not least
Machining & finishing: Applying the finishing touch
Machining and finishing are sometimes used to provide a thermoplastic part with a desired look or added functionality needed for assembly. These operations are more commonly used for fabricating prototypes and for trimming or modifying parts produced by thermoforming or extrusion. Injection-molded parts seldom need to be machined or finished.
Machining refers to a variety of material removal processes in which a cutting tool removes unwanted material from a part to produce the desired shape. Machining polycarbonate and polycarbonate blend parts may be cost prohibitive for large quantities, but is commonly used as a secondary process where minimal material is removed and the cycle time is short.
There are many machining processes. Some of the most common are:
- Drilling & Reaming – most frequently used to form holes in parts.
- Milling – used to remove large volumes of thermoplastic with relatively high accuracy and precision
- Turning – often used to manufacture round shapes
Annealing is an important step. Not all components require annealing, but annealing after machining helps achieve the lowest possible stress and the most stable component. Thermoplastic components polished without annealing may crack in operation.
Finishing operations, including polishing or buffing, can be used to repair abrasion or accidental surface scratches, finish holes and edges of polycarbonate parts, and create the desired surface appearance or texture. It is important to look at the heat-resistant properties of the material before selecting a finishing technique.
Covestro provides technical guidance to manufacturers related to machining and finishing polycarbonate parts.