CNC Machining of Engineering Plastics
Where metal brings conductivity, weight or corrosion, engineering plastics solve the problem differently: insulation, low friction, chemical inertness, radiolucency - if the machining keeps them dimensionally honest.
Why it is hard to machine
Plastics behave nothing like metals on a machine: they deflect under light loads, hold heat, relax after clamping and burr in materials-specific ways. Each family - POM, PET, PA, PEEK, PI, PTFE, PVDF - needs its own speeds, tooling and stress management.
Process controls that matter
Heat sensitivity
Plastics soften or melt long before metal would. Sharp tooling and controlled surface speed prevent smearing.
Clamping and stress
Low modulus means clamping itself deforms the part. Soft jaws, distributed force and staged machining keep geometry.
Material-specific deburring
Each polymer fuzzes differently. Deburring is matched to the material rather than applied generically.
Choosing a polymer: four things that decide it
Burrs, dimensional stability, performance and cost — what each one changes, and how we handle it.
| Consideration | What it affects | How we handle it |
|---|---|---|
| Burrs and cut edges | Plastics raise burrs and stringy edges more readily than metal, and a thin wall can move before the burr is even removed. | Sharp tooling with a positive rake, dry or low-temperature cutting, and edge control that removes the burr without bending the wall. Soft-brush or cryogenic deburring where blasting would embed particles. |
| Dimensional stability | Grades with higher moisture uptake keep moving after machining, so a dimension can be correct at delivery and different in your assembly. | We prefer low-absorption grades for tight-tolerance features and flag residual movement risk in the DFM review rather than leaving it to the batch. |
| Performance and duty cycle | Strength, temperature resistance, wear behaviour and chemical compatibility each pull the choice in a different direction. | We machine to your specified grade and certificate standard, and verify the incoming chemistry on the spectrometer before the material reaches a machine. |
| Cost and batch size | Material price, cycle time and tooling consumption together set the unit cost — and the material choice changes all three. | For prototypes we prioritise a route that proves the geometry; for recurring volumes we re-plan fixturing and tooling to bring the unit cost down. |
A qualitative guide for shortlisting materials. The final selection follows your duty cycle, your tolerances and our DFM review — tell us the application and we will narrow it down.
Tolerances, inspection and documentation
Typical applications
Electrical insulators, wear pads and bearings, fluid-handling parts, semiconductor and analytical components, medical and laboratory hardware.