Wholesale Price CNC Plastic Machining: 7 Checks Before You Order
This guide is for engineers and sourcing staff comparing suppliers of wholesale price CNC plastic machining. It lists the checks that decide whether a plastic part comes back on tolerance and on the quoted number.
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What decides a plastic part price
Comparing wholesale price CNC plastic machining options
| Resin | Machinable? | Best for | Watch out |
|---|---|---|---|
| ABS | Easy | Enclosures, fixtures | Low stiffness, creep under load |
| PC | Easy | Impact covers, lenses | Stress crazing near threads |
| PMMA | Easy | Optical windows | Chips; needs sharp tooling |
| POM | Easy | Gears, bushings | Hard to bond; poor paint adhesion |
| PA (nylon) | Moderate | Wear parts, clips | Absorbs moisture, grows 0.2–0.5% |
| PEEK | Moderate | Medical, high temp | Abrasive; tool wear raises cost |
| HDPE | Easy | Chemical tanks, liners | Flexes; hard to hold ±0.005 mm |
| Carbon fibre | Hard | Stiff lightweight frames | Dust control; edge delamination |
When the lowest quote is the wrong quote
If the drawing needs ±0.005 mm, an annealed blank, and a material certificate, buy on process control, not on the lowest number. If the part is a cosmetic cover with ±0.1 mm calls, buy on price and lead time.
Resin choice and wall thickness drive the number
Material is the first line on any plastic quote. A 100 × 100 × 20 mm block of POM and the same block in PEEK differ by roughly 8× in stock cost before a tool touches them. When a buyer asks for wholesale price on a plastic part, the fastest saving is usually a resin change, not a machine change.
Ask what the part actually does. A cover that shields a PCB does not need PEEK. A bushing running dry at 120 °C does. If the drawing says "engineering plastic" with no grade, expect two quotes: one cheap, one that survives the test.
Wall thickness matters as much as resin. Thin walls under 1.5 mm deflect during clamping and chatter during the finishing pass. Thick sections over 12 mm trap heat and warp after unclamping. Both cases push the price up because the shop has to slow down or add a stress-relief step.
We quote from the 3D file, so send STEP or X_T rather than a PDF drawing alone. A DFM note comes back with the price within 12 hours and flags any wall that will not hold tolerance.
Tolerance, finish and the second pass
Plastics are not metals. They spring back, they heat up, and they move after the cut. Holding ±0.005 mm on a plastic feature is possible, but it usually means a roughing pass, a cool-down, and a light finishing cut. That is a second operation, and it shows on the quote.
Be specific about which dimensions need the tight callout. Marking the whole drawing ±0.005 mm when only a bore and a mating face need it adds cost for nothing. Send the fit function instead: what slides, what presses, what seals.
Surface finish follows the same logic. Ra 1.6–3.2 μm is a normal as-machined finish on POM or ABS and costs nothing extra. Ra 0.8–1.6 μm needs a finer step-over and a sharper insert. Ra 0.2–0.8 μm on plastic is rare and often gets replaced by vapor polishing or a cast urethane route.
If the finish is cosmetic, say so. A visible face needs a different tool path than a hidden one, and mixing the two in one program wastes cycle time.
Order quantity and the real cost curve
Plastic machining does not behave like injection molding. There is no tool to amortize, so the price per part falls slowly. Setup, programming, and first-article inspection are shared across the run, and those are the same whether you order 5 parts or 500.
That is why wholesale price CNC plastic machining usually means a lower hourly rate and a lower material rate at volume, not a dramatic step down. Expect the second and third orders to be cheaper than the first, because the program and the fixture already exist.
No minimum order quantity matters here. We run one prototype and 10,000+ part runs on the same program. If your project is between a prototype and a mold decision, order 20 to 50 parts. That is enough to test assembly, drop, and thermal behavior without paying for tooling you may never use.
Batch size also changes inspection. A 10-part run can be checked 100% at the bench. A 5,000-part run needs a sampling plan agreed up front, or the inspection cost will surprise you at the end.
Certifications, paperwork and what a quote should include
For medical and automotive plastic parts, the certificate list is part of the price. We hold ISO 9001:2015, IATF 16949:2016, ISO 13485:2016, and ISO 27001:2022. That last one covers how your CAD files are stored and shared, which procurement teams ask about more often now.
Ask for the material certificate with the parts, not after. Resin lots vary, and a certificate of conformance with the lot number is what your own quality system will want to see. Inspection reports are available on request.
A quote that only lists a number is not useful. It should state the resin grade, the tolerance class, the finish callout, the inspection level, and the shipping window. If any of those are missing, the price is not comparable to the next supplier.
Confidentiality is part of the same conversation. Uploads are secure and confidential, and an NDA is available on request before you send a file.
Seven steps from RFQ to shipped plastic parts
- 1Send STEP plus a function noteInclude the fit callouts and the resin grade if you have one. A PDF alone forces us to guess.
- 2Read the DFM noteCheck flagged walls under 1.5 mm and any feature that needs a second setup.
- 3Confirm the resinCompare grade, not family. POM-C and POM-H machine differently and cost differently.
- 4Mark tight dimensions onlyKeep ±0.005 mm on mating features. Let cosmetic and clearance faces sit at ±0.1 mm.
- 5Agree the inspection level100% inspection before shipment is standard. For large runs, fix the sampling plan in writing.
- 6Approve the first articleMeasure the critical features before the run continues. Fix the program, not the parts.
- 7Ship and reviewParts ship in 3–5 days after approval. Keep the inspection report with the lot.
Questions buyers ask about plastic machining quotes
Why is a plastic part sometimes priced higher than the same part in aluminum?
Plastic stock can cost more per kilogram than 6061 aluminum, and it machines slower. PEEK and carbon-filled resins wear tooling fast, so the shop has to slow the spindle and change inserts more often.
Add the annealing step and the extra care in clamping, and a PEEK part can land above the aluminum version even though it weighs less.
Can you hold ±0.005 mm on nylon or HDPE?
On a dry, stabilized part, yes. On a part that will sit in humid air, no. Nylon absorbs moisture and grows 0.2–0.5% over weeks, which is far more than the tolerance.
For those resins we machine to a stable nominal, note the growth direction on the drawing, and let the end user confirm the fit after conditioning.
What is the smallest order you accept?
There is no minimum order quantity. One prototype is fine. The setup cost is the same, so the per-part price is higher at one piece than at fifty.
Most projects start with 5 to 20 parts to validate the design before committing to a larger run.
Do you provide material and inspection certificates?
Yes. Material certificates with lot numbers travel with the parts, and inspection reports are available on request.
Every order gets raw material check, in-process monitoring, and final inspection before shipment.
How do you handle confidential CAD files?
Uploads are secure and confidential, and our information security management system is certified to ISO 27001:2022.
If your legal team needs a signed NDA before the file moves, we can do that first.
Which plastics do you machine most often?
ABS, PC, PMMA, POM, PA, PEEK, PP, HDPE, and carbon fibre composites. Aluminum and stainless grades are handled on the same floor if the part is a hybrid assembly.
Send the resin grade if you already have one. If not, describe the temperature, load, and chemical exposure and we will suggest one.
Send the file and get a number back in 12 hours
Upload your STEP file and get a quote with a free DFM analysis, a stated resin grade, and a fixed inspection level.
12-hour quote100% inspectionNo MOQNDA on request
More machining notes
We publish setup notes, tooling trials and inspection data from the factory floor.
