CNC Machining Plastic Materials

CNC Machining Plastic material

Picture	Material	Details	Service
	ABS	The opaque thermoplastic, it is an amorphous polymer comprised of three monome	CNC machining
	Polycarbonate (PC)	Strong, tough materials, and some grades are optically transparent.	CNC machining
	PMMA (Acrylic)	It is a transparent thermoplastic, used as an engineering plastic.	CNC machining
	Polypropylene (PP)	Slightly harder than polyethylene, a commodity plastic with low density and high heat resistance. application in packaging, automotive, consumer goods, medical, cast films, etc.	CNC machining
	Nylon	Excellent abrasion resistance, high impact strength and good mechanical properties.	CNC machining
	POM	High mechanical strength and rigidity. POM material has very good sliding properties, excellent wear resistance and low moisture absorption.	CNC machining
	PTFE (Teflon)	Being hydrophobic, non-wetting, high density and resistant to high temperatures, PTFE is an incredibly versatile material with non-stick properties.	CNC machining
	Polyethylen (PE)	It is available in different crystalline structures, referred to as HDPE, LDPE, and LLDPE.	CNC machining
	Bakelite	The thermosetting phenol formaldehyde resin, formed from a condensation reaction of phenol with formaldehyde	CNC machining
	Carbon Fiber	Strong, lightweight, and stiff material that is made from thin, strong crystalline filaments of carbon.	CNC machining

How Engineering Plastics Behave on a CNC Machine

Plastic parts are not "easy metal". They cut at completely different feeds and speeds, and they bring problems metal never shows. Understanding those problems is the difference between a clean part and a scrapped one.

Heat, not chips, is the enemy. Plastics do not conduct heat away like metal. Too high a surface speed melts the edge, smears the surface and welds swarf back onto the part. Sharp tools, high feed and generous coolant or air blast keep the cut cool.
Clamping forces distort the part. Soft material squeezes under a vice, so the finished part springs back out of tolerance once released. We use light, distributed clamping and often machine from soft jaws.
Burrs are stringy. Instead of a crisp burr, many plastics raise a fine fuzz that is hard to remove. Sharp geometry, controlled feed and a light finishing pass minimise it.
Thermal expansion is large. Plastic grows and shrinks far more than metal with temperature. Measurements taken hot are misleading, and tight tolerances must be verified at a controlled temperature.

Plastic vs Metal: When Plastic Wins

Engineered plastics replace metal whenever the load is moderate and one of these benefits matters more than raw strength:

Weight reduction — roughly one-sixth the density of steel.
Electrical and thermal insulation — no short circuits, no heat bridges.
Chemical resistance — PTFE and PEEK shrug off aggressive media.
Low friction and self-lubrication — bushings, wear pads, rollers.
No corrosion — no plating, no painting, no rust.
Quiet, forgiving contact — gears and guides run smoother and quieter than metal.

Selecting a Plastic: Decision Guide

Material	Strength / stiffness	Heat resistance	Best known for
ABS	Medium	Low	Tough, low-cost housings and covers
POM (Delrin)	High	Medium	Gears, bushings, precision sliding parts
PC (Polycarbonate)	High	Medium	Impact-resistant windows and guards
PMMA (Acrylic)	Medium	Low	Optically clear panels and lenses
PA (Nylon)	High	Medium	Wear parts, rollers, tough mechanical parts
PTFE	Low	High	Chemical seals, low-friction bearings
PEEK	Very high	Very high	Aerospace, medical and high-temperature parts

Machining Tips for Plastics

Use polished, sharp tooling. Dull edges rub rather than cut and generate heat.
Feed hard, spin slow. A thick chip carries heat away with the swarf; a light rub melts the surface.
Cool with air first. Compressed air suits most plastics; flood coolant helps on PEEK and other heat-sensitive grades.
Deburr with care. A sharp scraper or a flame-polish pass removes fuzz that sandpaper only spreads.
Allow for movement. On a part that must fit metal hardware, design a little clearance rather than assuming a press fit will hold.

Frequently Asked Questions

Can you hold the same tolerances in plastic as in aluminium?

For a stable, well-supported plastic part, yes — ±0.05 mm is routine. Very thin or flexible features are limited more by the part's stiffness than by the machine.

Which plastic is best for a gear or a bearing surface?

POM (Delrin) is the usual first choice for gears and sliding parts, with nylon for higher loads and PEEK where temperature or chemical exposure rules out the others.

Will the part warp after machining?

Machined plastic can relax and move slightly as internal stresses release. For tight parts we rough-machine, let the part rest, then finish — a two-stage process that trades a little time for stability.

Do you offer the same finishes as on metal?

Painting and laser marking are common; anodising and plating are metal-only processes. Where a plastic part needs a colour or a matte look, we tint or bead-blast it instead.

CNC Machining Plastic Materials