Machining

Machining is often necessary for fabrication processes like blow molding and extrusion. Injection molded parts normally do not require any machining operations, apart from removal of sprues and flash in some cases.

The following are recommended for machining plastic parts.
- Standard HSS (high speed steel) tools or carbide tools used for machining metals can generally be used, although specially designed tools for plastics may sometimes allow higher production rates and have better chip removal capabilities. Carbide tipped tools and diamond tools offer a longer tool life and are especially suited for filled polymers.

- Cutting oils and cooling liquids used in the metal industry should generally be avoided, as they may not be chemically compatible with plastics and must be removed afterwards. A forced air stream can best be used for cooling, or if more intensive cooling is necessary, a water spray mist or a water soluble cooling liquid can be used.

- In machining plastics it has to be remembered that the heat conductivity of these materials is only one hundredth to one thousandth of that of metals. A high cutting speed and a low feed speed are therefore customary, and sharp and well polished tools are required in order to avoid local melting and gumming. Cutting tools must have a generous back clearance to minimize frictional heating.

- Plastics generally have a high thermal expansion coefficient, up to a factor twenty higher than that of metals. The dimensions of machined parts should therefore be measured after allowing the parts to cool down.

- Internal stresses are built up in the plastic part during machining. Annealing may therefore be considered in critical cases, where environmental stress cracking can be expected. This can be critical for Xantar PC.

- Skin contact and inhalation of dust must be avoided, as dust may cause irritation. Please check the material safety data sheets for required precautions.

There are a number of machining methods:

Drilling and reaming, Threading and tapping

Cutting operations
Sawing
Laser cutting
Milling
Turning and boring
Punching, blanking, and die cutting

Polishing operations
Filing
Sanding and grinding
Polishing and buffing