Chinese carbon fiber capacity has grown fast, and so have the differences between workshops. The gap between a factory that lays up and cures in-house and one that resells another factory's stock is invisible in a quotation — but very visible in your third shipment.
Samples are hand-made and beautiful; production is porous and off-tolerance. Grade is vague. Tooling reappears in a competitor's catalogue. Nobody is on the hook when a container arrives wrong. Every fear is fixable with information — which is what this checklist forces out.
Use it as a scoreboard. Ask each supplier the same seven questions, write the answers side by side, and the shortlist usually makes itself. If a supplier will not answer any of these, that answer is itself the most useful data point.
| Check | Ask This | Good Answer |
|---|---|---|
| 1. Real factory? | Video walkthrough of the layup floor and equipment list | Willing to film your actual order being made, names their own machines |
| 2. In-house process | Do you wrap, cure and machine yourself, or subcontract? | Clear statement of each step done on site, and which are outsourced |
| 3. Material grade | Which fiber and resin exactly? | Named fiber grade and resin system in writing, with alternatives offered |
| 4. Consistency | How do you guarantee batch 5 matches sample 1? | Written layup schedule, batch records, first article inspection |
| 5. Tolerance | Which tolerances do you hold and how is it measured? | Numbers for OD, ID, wall, straightness — plus the measuring equipment used |
| 6. Commercials | MOQ, tooling ownership, payment terms | Negotiable small runs, tooling owned by you, sensible deposit structure |
| 7. Protection | What happens if the container arrives wrong? | Defined inspection window, replacement policy, and NNN-style confidentiality |
Both can deliver good parts, but only quote apples to apples. A trading office packages well and communicates fast — then hands your jam to an unknown production floor. Ask for the machine list and a live video call from the workshop. If it is a trading relationship, that is fine, but you should know it before you plan your supply chain.
"Carbon fiber" is not a specification. Named fiber grade, resin system and cure cycle are. Tell your supplier the grade you need — Toray and Mitsubishi grades where properties are critical, or Chinese equivalents where cost drives the design — and require it stated on the quotation and the packing documents.
This is the single most common failure. A hand-made prototype proves the design; it does not prove the process. Ask for a first article from production tooling, batch records, and the layup schedule in writing. Where volume justifies it, use third-party inspection before shipment.
Dimensional drift is what actually stops an assembly line. Have the supplier commit to numerical tolerances on OD, ID, wall thickness, straightness and concentricity, and ask what equipment measures them. Vague promises like "high precision" are worth nothing when parts do not fit your fixture.
Tooling paid by you should be yours, stated in writing. For custom layups and drawings, use an NNN agreement (non-use, non-disclosure, non-circumvention) drafted to be enforceable in China — a Western NDA is often hard to enforce locally. A supplier who refuses normally has a reason.
Typical structures for new relationships are a deposit with balance against shipping documents, often with samples paid fully in advance. Anything demanding 100% upfront with no traceable company history is a reason to slow down. Third-party inspection and milestone photos cost little and protect both sides.
Composite parts generally ship under HS heading 6815.99 in the EU, but confirm the classification your market uses. Check resin compliance requirements such as REACH and RoHS, ask about wooden packaging rules, and prefer suppliers who have already shipped to your region and can quote both FOB and DDP terms.
Time zone is not the problem; silence is. A serious supplier replies within a working day, owns one direct contact, and answers technical questions rather than re-quoting. Test it early: ask one specific engineering question and see whether you get an explanation or a price.
Suppliers quote accurately when the request is complete. Missing information is either assumed — usually wrong — or priced as risk.
Step or DXF drawing, or a dimensioned sketch. Include OD, ID, wall thickness, length, straightness and surface finish — gloss, matte or peel-ply.
What the tube actually does: pure axial load, bending, torsion, impact, fatigue or temperature. This is what determines layup, not the drawing.
Sample quantity, first production quantity, expected repeat volumes and your target delivery date. Suppliers tailor tooling and process to real volumes.
Any required fiber grade or resin system, plus the properties you must meet — stiffness, strength, temperature resistance or electrical insulation.
| Red Flag | What It Usually Means |
|---|---|
| Refuses workshop video | No production floor, or not the one making your parts |
| Vague material grade | Generic or substitute materials swapped later |
| No tolerance figures | Dimensional control is not being managed |
| Only answers with prices | No engineering backing; expect surprises in production |
| 100% upfront, no history | Highest-risk payment structure available to you |
| No written quality terms | No defined remedy if a batch is wrong |
Yes, provided you apply normal due diligence: verify the supplier actually produces rather than resells, get the fiber grade and resin system stated in writing, agree numerical tolerances, use a first article inspection before the production run, and structure payment so the balance is released against documents or inspection.
Ask for a live video walkthrough of the layup and curing area and for their equipment list. A factory names its own machines and can film your order in progress. Also ask explicitly which steps are subcontracted — most workshops outsource some operations, and knowing which ones matters for delivery control.
Because "carbon fiber" is not a specification. Fiber grade sets stiffness and strength, while the resin system sets temperature resistance and toughness. Suppliers can substitute cheaper equivalents without changing the appearance, so the grade must be named on the quotation and packing documents.
Insist that samples come from production tooling and not from hand layup, request the written layup schedule and batch records, and add a first article inspection that you approve before the rest of the batch runs. For higher volumes, use third-party inspection before shipment.
Reputable suppliers hold around ±0.1 mm on CNC-cut lengths, holes and contours, with typical raw tube wall tolerance near ±0.05 mm, and will quote straightness and concentricity figures. Always ask what equipment measures these values, and get the numbers on the quotation rather than general claims of high precision.
For a new relationship, a common structure is a deposit with the balance paid against shipping documents or third-party inspection approval, with samples usually paid fully in advance. Be cautious of any demand for 100% upfront payment without a traceable company history.
Use an NNN agreement covering non-use, non-disclosure and non-circumvention, drafted to be enforceable under Chinese law rather than relying on a standard Western NDA. Also agree in writing that tooling you pay for belongs to you and will not be used for other customers.
Carbon fiber articles are commonly classified under HS heading 6815.99 for EU import, though classification depends on the specific product and construction. Confirm the code with your customs broker, and ask the supplier to state the same code on their commercial invoice.
Most suppliers will run a prototype or pilot batch before committing to volume, and some quote minimums as low as 10 pieces. Make the pilot explicit: agree that qualification results carry over to the production run, and keep the same layup and tooling.
