China can be competitive for custom sheet metal parts, but the lowest quotation is not always the lowest landed cost. A useful supplier comparison starts with the same technical package and a clear manufacturing and inspection scope.
Build a complete RFQ package
Send the STEP or DXF file, material grade, thickness, quantity, finish, critical tolerances and required delivery date. If the part is a replacement for an existing machine component, state whether fit is controlled by a sample, drawing or both.
Include a 2D drawing where tolerance, thread, hardware or cosmetic requirements cannot be expressed in the 3D file alone.
Ask how the quotation was built
A transparent quotation explains material, cutting route, bending, welding, finishing, inspection and packing assumptions. If the price depends on a minimum quantity or an outsourced finish, ask for that threshold in writing.
Also confirm the Incoterm. EXW, FOB and DDP prices are not comparable, and the buyer may carry different responsibilities for freight, insurance, duty and customs clearance.
Compare lead time in stages
Ask for:
- engineering and DFM review time
- sample or first-article time
- production time after approval
- finishing time
- packing and freight transit time
Treating all of these as one vague “lead time” hides the real bottleneck.
Verify quality before volume
Request the inspection plan before production. For a new supplier, a paid sample or first article is cheaper than discovering a process problem after a full batch.
Ask whether dimensional reports, material certificates, first-article inspection records and pre-shipment photos are available. The answer should identify who checks the part and what happens when it is out of specification.
Protect drawings and intellectual property
Use an NDA where the design is sensitive. Confirm that drawings will not be shared publicly and that customer parts will not be used in marketing without written permission.
Never outsource a safety-critical or patented part without confirming the customer’s right to reproduce it.
Check export packing
Ask how edges, powder-coated surfaces, threaded features and small hardware are protected. Confirm carton dimensions, weight, pallet or crate requirements and whether the packing can survive the selected freight mode.
Questions worth asking every supplier
- Which operations are in-house and which are outsourced?
- What is the real production lead time after drawing approval?
- Which inspection records are supplied?
- What is the MOQ for this material and finish?
- What Incoterm, freight mode and packing are included?
Best practice: make the first order a controlled pilot. Approve the drawing, the first article and the packing before releasing repeat volume.
