PEEK & Engineering Plastics CNC Machining

If you've only machined metal, the first time you cut PEEK you'll think the machine is broken. No chips — just white dust. The tool doesn't sing — it squeaks. And if you're not careful, the edge of your part will look like it was chewed off rather than machined.

Plastics behave differently from metals in three important ways. First, they don't conduct heat. All the cutting energy stays at the tool tip, so the plastic can melt and smear rather than shear cleanly. The solution is sharp tooling with polished flutes, coolant at low pressure (high pressure blasts the part off the fixture), and chip loads high enough to actually cut rather than burnish.

Second, plastics spring back more than metals. After the tool passes, the material relaxes and the hole or pocket closes up slightly. We compensate in CAM by over-cutting spring-back areas by 0.02-0.05mm depending on the material. PEEK has less spring-back than UHMW, but both require compensation that isn't needed for aluminium.

Third, chip control is completely different. You can't break a plastic chip — it either powders (brittle) or strings (tough). PEEK produces short, powdery chips that can clog coolant nozzles. Nylon produces long strings that wrap around everything. We run dedicated plastic-only machines with chip extraction systems. No cross-contamination with metal chips.