China CNC Plastic Parts Manufacturer
This page is for design engineers and sourcing teams who need machined polymer components from a Chinese supplier. It covers which plastics cut well, what tolerance and surface finish you can hold, how to inspect the parts, and when a machined plastic part is the wrong choice. Read it to judge whether your drawing fits our process before you send an RFQ.
What This Page Covers
Machined polymers, not molded ones. If your part is molded, this is the wrong page.
When Machining Beats Molding for Plastic Parts
CNC machining removes material from a solid block with a rotating cutter. For plastics that means no tooling cost, no mold lead time, and no minimum order quantity. GreatLight runs from one prototype to 10,000+ part runs, so a design change after the first article only costs you a new program, not a new mold.
The trade-off is cycle time. A molded part pops out in seconds; a machined one can take minutes to hours depending on cavity depth and feature count. Machining wins when the geometry is complex, the volume is low to medium, or the material is hard to mold. It loses when you need 100,000 identical simple parts.
Plastics behave differently from aluminum on the machine. They spring back, they hold heat, and they chip instead of curling. A cutter that works on 6061 will burn POM. This is why polymer jobs need their own feeds, speeds, and fixturing, not a metal program with the feed override turned down.
- 1Good fitBrackets, housings, insulators, manifolds, jigs, and prototype enclosures with pockets and ribs.
- 2Weak fitThin walls under 0.8 mm, deep narrow slots, and parts that must flex repeatedly in service.
- 3VolumePrototype through 10,000+ parts. Above that, compare against injection molding.
Plastic Grades We Machine and How They Cut
Material choice drives the whole job. ABS is the default for functional prototypes and covers most enclosures, but it is not stiff and it creeps under load. PC is much tougher and holds tolerance better, though it is notch sensitive and needs sharp tooling. POM machines cleanly, holds tight tolerances, and slides well, which makes it the pick for gears, bushings, and wear strips.
For higher temperatures, PA and PEEK are the common answers. PA absorbs moisture and will move after machining unless you dry it and account for the growth. PEEK is expensive, abrasive to tooling, and usually reserved for medical, aerospace, or semiconductor parts where temperature and chemical resistance matter more than cost.
PMMA gives optical clarity and takes a polished edge, so it suits light guides and display covers. PP and HDPE are chemical resistant and cheap but soft, and they are difficult to hold to tight tolerance because they deflect under the cutter. Carbon fiber stock cuts as a composite, not a plain polymer: abrasive, dusty, and prone to delamination at the edges.
- 1ABSPrototypes, enclosures. Easy to cut, low stiffness, creeps under sustained load.
- 2PCImpact resistance and dimensional stability. Notch sensitive; use sharp tools.
- 3POMGears, bushings, wear parts. Holds ±0.005 mm well on stable geometry.
- 4PEEK / PAHigh temperature and chemical exposure. PEEK is costly and abrasive.
Plastic Selection Quick Reference
Practical guidance for a 50 mm bracket with a 6 mm wall.
| Plastic | Best for | Machining note |
|---|---|---|
| ABS | Prototypes, enclosures, covers | Easy to cut; low stiffness |
| PC | Impact parts, clear guards | Sharp tools; stress cracks at sharp corners |
| POM | Gears, bushings, wear strips | Clean chips; stable at ±0.005 mm |
| PMMA | Light guides, display windows | Polishes well; brittle at thin sections |
| PA | Structural brackets, ducts | Absorbs moisture; dry before final cut |
| PEEK | High-temp and chemical service | Abrasive; slow feeds, carbide tooling |
| PP / HDPE | Chemical tanks, liners | Soft; hard to hold tight tolerance |
| Carbon fiber | Stiff lightweight panels | Abrasive dust; edge delamination risk |
Tolerance, Surface Finish, and Machine Limits
Our general machining tolerance is ±0.005 mm on metal, and we apply the same target to rigid plastics such as POM and PC when the geometry allows. Soft grades like PP and HDPE will not hold that over a long span regardless of who machines them. Tell us the functional dimension and the fit it works against, and we will flag what is realistic before cutting.
Surface finish ranges from Ra 0.2–0.8 μm on a fine cut to Ra 1.6–3.2 μm as machined. Plastics polish faster than metals, so a decorative finish is usually cheaper here than on an aluminum part. Laser marking is available down to a minimum character height of 1.5 mm. Anodizing and plating do not apply to polymers; bead blasting, tumbling, and polishing do.
Size is rarely the constraint. We machine up to 4,000 mm, with three-axis travels of 4,000 × 400 × 150 mm, 750 × 1,150 × 550 mm, and 600 × 600 × 600 mm. Sixteen simultaneous 5-axis centers handle undercuts and angled faces in one setup, which matters for plastic parts because every re-clamp risks a witness mark. A Ø400 mm rotary table covers round and indexed features.
Wall thickness is the practical limit, not the envelope. Plastics deflect under cutting force, so walls under 0.8 mm tend to chatter and burn. Deep pockets need a stub cutter, which limits reach. If your part has a 0.5 mm wall and a 40 mm deep slot, expect a design conversation rather than a quote.
- 1Tight tolerance±0.005 mm (±0.0002 in) on rigid grades with stable geometry.
- 2Fine finishRa 0.2–0.8 μm on request; Ra 1.6–3.2 μm as machined.
- 3Large partsUp to 4,000 mm, including long extrusions and panels.
- 45-axis16 simultaneous centers for undercuts and single-setup finishing.
Inspection and Documentation for Plastic Parts
Every part is inspected before shipment, and inspection reports are available on request. The sequence is raw material check, in-process monitoring, then final inspection. For plastics we also log the stock batch, because two deliveries of the same grade can machine differently if moisture content or pigment loading changes.
Critical dimensions are measured against your drawing, not against a nominal model. If a feature is not toleranced, we hold the general tolerance and note it. For medical and automotive programs, the inspection plan is written from the drawing's control dimensions so the report maps one-to-one to the print.
GreatLight holds ISO 9001:2015, IATF 16949:2016, ISO 13485:2016, and ISO 27001:2022. That last one covers how we handle your CAD data: uploads stay confidential, and an NDA is available on request. Three wholly-owned plants and 150 technicians sit behind the process, in Dongguan and Singapore.
Our historical late-delivery probability is below 2%. Quotation and a free DFM analysis come back within 12 hours, production can start within 24 hours, and parts ship in 3–5 days. Those are typical figures, not a guarantee on every geometry.
- 1100% inspectionRaw material, in-process, and final checks before shipment.
- 2Reports on requestDimensional data mapped to your control dimensions.
- 3ConfidentialitySecure uploads; NDA available. ISO 27001:2022 certified.
What to Send for a Fast, Accurate Quote
Send a STEP or IGES file plus a 2D drawing with tolerances. A model alone tells us the shape; the drawing tells us which dimensions actually matter. If you only have a model, say so, and we will apply general tolerances and flag the risky features in the DFM note.
State the plastic grade, the quantity, and the function. "POM, 50 pieces, slides against a steel shaft" tells us more than a material code alone. Mention any post-machining step such as bead blasting, polishing, or laser marking, and include the surface finish target if it is cosmetic.
You get a quotation and a free DFM analysis within 12 hours. The DFM note lists thin walls, deep pockets, sharp internal corners, and features that will need a second setup. Fixing those before the first cut is cheaper than fixing them after. No minimum order quantity applies, from one prototype upward.
- 1FilesSTEP or IGES plus a 2D drawing with tolerances and finish callouts.
- 2ContextMaterial grade, quantity, and what the part does in the assembly.
- 3FinishBead blasting, tumbling, polishing, or laser marking to 1.5 mm minimum height.
Common Questions from Engineers and Buyers
Can you hold ±0.005 mm on any plastic?
No. That tolerance applies to rigid grades such as POM, PC, and PEEK on stable geometry with a reasonable wall. Soft materials like PP and HDPE deflect under the cutter and will not hold it over a long span.
Send the drawing and we will tell you which dimensions we can hold and which need a looser callout before we quote.
What is the minimum order quantity for China CNC plastic parts?
There is no minimum. We run from a single prototype to 10,000+ part runs on the same program.
For very low volumes, expect a slightly higher unit price because setup and programming are spread over fewer parts.
How do you stop plastic parts from warping after machining?
We control it in three ways: rough cut, stress relief where the material allows, then finish cut. We also avoid removing more than about a third of the wall in one pass.
PA and similar moisture-absorbing grades are dried before the final cut so the part does not shrink after shipment.
Which plastic should I pick for a wear part?
POM is the usual answer for gears, bushings, and slide strips. It holds tolerance, has a low friction coefficient, and machines cleanly.
For higher temperature or chemical exposure, PEEK is the next step up, at a much higher material cost.
Do you offer anodizing or plating on plastic parts?
No. Anodizing and electroplating are metal processes. For polymers we offer bead blasting, tumbling, brushing, polishing, and laser marking.
Laser marking has a minimum character height of 1.5 mm.
How do you protect my design when I upload files?
Uploads are handled as confidential. We hold ISO 27001:2022 for information security and will sign an NDA on request.
Your files are used for quoting and manufacturing only, and are not shared outside the project team.
Send Your Plastic Part Drawing
Quotation and free DFM analysis within 12 hours. No minimum order quantity.
12-hour quote100% inspectionNDA available
