If you are buying custom CNC parts, stamped brackets or sheet metal enclosures from China, finding a factory is the easy part. The hard part is getting three quotes you can actually compare, and then receiving parts that match the drawing when the shipment lands. Those two outcomes are decided before you place the order, by six decisions: the RFQ pack, the manufacturing cluster, factory verification, landed cost, quality gates and consolidation.
We should say up front who we are. CinoSourcing is a sourcing and freight team based in Shenzhen, not a machine shop. We sit on the buyer’s side of the table. Since 2019 we have run these checks for 4,000+ buyers shipping to 200+ countries, and the checklist below is the one we use before a deposit leaves a client’s account.
- Build a complete RFQ pack before you contact anyone.
- Shortlist factories in the cluster that actually makes your part type.
- Verify the legal entity, the equipment and the certificates before paying.
- Compare quotes on total landed cost, never on unit price alone.
- Write three quality gates into the purchase order: sealed sample, first article, pre-shipment inspection.
- Consolidate parts from several factories into one shipment with one customs entry.
Start with the RFQ pack, not the supplier list
Most quote variance between suppliers comes from ambiguity in the drawing, not from differences in shop efficiency. Send ten factories a screenshot and you will get ten numbers that mean ten different things. Send them the same complete package and the spread narrows enough to be useful.
A package we consider quotable contains:
- 3D model in a neutral format — STEP AP214 preferred; native SolidWorks or Fusion files help but do not replace STEP. IGES and DXF for 2D profiles.
- 2D drawing with title block, revision, datums, general tolerance, critical dimensions and full thread callouts. “M4” is not a specification; state the class, depth and whether the thread is cut or roll-formed.
- Material grade and condition — 6061-T6, not “aluminium”; 316L, not “stainless”. Note the acceptable substitute, if there is one.
- Surface finish per feature, not per part. Give an Ra value where it matters and say “as machined” elsewhere. “Smooth” and “deburr all edges” are not measurable and will be interpreted in your supplier’s favour.
- Quantity breaks in one request — ask for 1, 10, 100 and 1,000 in a single RFQ so you can see how setup cost amortises.
- Inspection requirements — first article only, sampling to an agreed AQL, or a full dimensional report.
- Packaging, destination and Incoterm — protective packaging, consolidation needs, and who is responsible for duties.
- Application context — what the part does, which face is cosmetic, and any certification the end product needs.
One line in the RFQ saves more rework than any price negotiation: “Please flag any feature that will increase cost or lead time before quoting.” A shop that comes back with questions has read your drawing. A quote that arrives in ten minutes with no questions usually means nobody opened it.
Match the part to the right manufacturing cluster
China is not one market. Sending an enclosure drawing to a cluster built around consumer electronics wastes a week. Our own sourcing hub map on our homepage is a reasonable starting point:
| Part type | Where we usually start | Why |
|---|---|---|
| Custom OEM parts, moulds and tooling | Dongguan | Dense toolroom and mould-making capacity, used to build-to-print work. |
| Hardware, auto parts, plastic injection | Ningbo | Hardware and injection supply chain in one place. |
| Electronics and assemblies | Shenzhen | Component availability and fast prototyping loops. |
Treat that as a filter, not a rule. A good part may still be made two cities away, and a named cluster is no substitute for checking the actual machine list. What you are buying is process fit, not a postcode.
Verify the factory before you send a deposit
A business licence proves that a company exists. It does not prove it owns the machines in the photographs, or that the ISO certificate covers your part. Six checks, in order:
- Match three names — the legal entity on the licence, the factory address, and the name on the bank account you are being asked to pay. A mismatch at this stage is the most common first-order problem we see.
- See the floor live — a video walkthrough is enough for a first pass. Ask to see the metrology area, not just the machines. A shop with no measuring equipment cannot hold the tolerance it is quoting.
- Check certificate numbers and scope — ISO 9001 is the floor, not a differentiator. Automotive, aerospace and medical work need IATF 16949, AS9100 or ISO 13485 with a scope that covers the actual process. Ask for the PDF and the last surveillance audit date.
- Ask a technical question — how would they hold flatness on a thin wall, or machine a deep pocket with a small internal corner? A real process engineer will answer in specifics. A trading company will go quiet or forward the question on.
- Ask for material traceability — mill test reports to EN 10204 3.1 for the heats used in your batch, plus a sample inspection report from a previous job.
- Confirm who does the secondary operations — heat treatment, anodising, plating and welding are often subcontracted. Find out who is accountable when a finish fails.
We keep the full version of this as a separate Chinese factory verification checklist; the checks above take about fifteen minutes and are the ones that matter before money moves.
Compare quotes on landed cost, not unit price
A unit price is one line in a much longer invoice. Ask every supplier to itemise the following, then compare the totals:
| Line | What buyers usually miss |
|---|---|
| Part price at each quantity tier | Whether the quote assumes a material substitute or a looser tolerance than the drawing. |
| Tooling, fixtures and programming (NRE) | Whether it is a separate charge or quietly amortised into the unit price. |
| Secondary operations | Deburring, anodising, powder coating, passivation, plating — often quoted as optional, then needed. |
| Inspection and documentation | CMM time, first article report, material certificates. |
| Packaging and inland trucking | Rust prevention, separators, carton strength, palletisation, factory to port. |
| International freight and insurance | Chargeable weight, port charges, surcharges. |
| Duties, customs fees and brokerage | Often the single largest variable, and the one most often left out entirely. |
| Final-mile delivery | Drayage, delivery appointment, storage if clearance is delayed. |
A quote 40% below the cluster is rarely an efficient factory. It is usually a missing finishing step, an assumption about material, or an inspection plan that does not exist. We break the duty and freight side down in a separate landed cost guide.
Put three quality gates into the purchase order
Inspection at the end cannot repair a process that drifted for three weeks. Write these three gates into the order, with the drawings and revision numbers attached:
1. A sealed sample made by the production process
A hand-finished prototype confirms the shape. It tells you nothing about whether the production route can hold it. A laser-cut trial part, for example, will not prove that a stamping die controls burrs and hole position. Approve design on one sample, then approve a second sample made with the intended process, material and finish. Keep the approved one sealed and dated.
2. First article inspection (FAI)
Before the full run, ask for a report that maps measured results to numbered drawing characteristics, and states the drawing revision, instrument, sample number and date. A table of numbers with no characteristic references is impossible to audit later. For a new die or fixture, this is also where you find out whether the tool was built to your interpretation of the drawing.
3. Pre-shipment inspection (PSI)
Agree the sampling standard, inspection level and AQL in writing, and define defect severity before production starts — a cosmetic scratch on a hidden bracket is not the same as a wrong thread on a load-bearing feature. We inspect every shipment to AQL 2.5 against the approved sample: function, appearance, dimensions, quantity, packaging and carton marks. The dated photo report goes to the buyer, and nothing ships on our decision alone.
Consolidate before you ship
Real projects rarely come from one factory. A single product might need laser-cut brackets, CNC-turned fasteners and powder-coated housings, each from a different shop. Left uncoordinated, that becomes three shipments, three customs entries and three sets of paperwork.
Our Shenzhen warehouse collects from each supplier, checks the parts against their own approved samples, repacks to the destination spec (including FNSKU labelling and carton marks for Amazon FBA where needed), and consolidates everything into one shipment with one customs entry and one tracking link. For buyers who do not want to manage customs at all, we quote DDP door-to-door with duties stated up front rather than as a surprise invoice after delivery.
Five mistakes we see on first orders
- Choosing on unit price. One rejected shipment wipes out a 10% saving several times over.
- No revision control. The sample, the PO and the drawing in the factory’s inbox are three different versions. State the revision in every document.
- Paying 100% up front. Agree staged terms tied to sample approval and shipment release instead.
- Accepting “we check every part” as a quality plan. A plan names the standard, the frequency, the characteristics and the documents you will receive.
- No tooling clause. For stamped or moulded parts, state in the PO who owns the die, where it is stored, who maintains it, and whether it can be used for another customer.
Frequently asked questions
What files do I need to get an accurate quote for custom metal parts?
A neutral 3D model (STEP AP214), a dimensioned 2D PDF with GD&T and revision, exact material grade and condition, surface finish per feature, quantity breaks, inspection requirements and the delivery destination. Without the 2D drawing, critical tolerances and thread classes are guesswork, and suppliers will price that uncertainty into the quote.
How do I know if a Chinese supplier is a real factory?
Match the legal entity, factory address and bank account name; request a live video walkthrough including the metrology area; verify certificate numbers and scope; and ask a process-specific technical question. A trading company can still be a useful single point of contact, but you should know which one you are dealing with and where the markup sits.
What is a reasonable MOQ for custom CNC parts?
Do not negotiate a single MOQ. Ask for pricing at 1, 10, 100 and 1,000 pieces in one RFQ. Setup and programming are fixed costs, so small runs look expensive per part while the tooling-free route stays flexible — the tiered quote shows you where the economics change for your specific geometry. Any number quoted without your drawing is a marketing figure, not a commitment.
Who pays import duties on a DDP shipment?
The supplier does, in principle. In practice, insist that the quote explicitly lists duties and taxes as included, names the broker handling clearance, and states the Incoterm in the PO. A vague “DDP included” that later produces a customs bill is not DDP. If you have your own broker and want visibility into the duty breakdown, DAP or FOB may suit you better.
Can I protect my CAD files when sourcing from China?
Sign an NDA with the supplier’s legal entity, share watermarked PDFs until a contract is in place, ask how drawing access is controlled internally, and state in the PO who owns the tooling, fixtures and machining programs. Reputable shops treat this as standard practice rather than an accusation.
If you have a drawing, or just a photo and a rough description, send it with your target quantity and destination country. We shortlist vetted factories, show the factory invoice separately from our fee, and come back within 24 hours with a comparison you can audit line by line. Send your requirement and we will start at step one.