Choosing the wrong supplier costs far more than the parts. Use this checklist to evaluate a Chinese custom-parts manufacturer before you commit.
1. Manufacturer or trading company?
Confirm whether they actually make the part in-house or resell it from another factory. In-house manufacturing usually means better control over quality, lead time, and communication. Ask about their workshops, equipment, and capacity.
2. Relevant certifications
For heavy-machinery and vehicle parts, look for ISO 9001 (quality management) and IATF 16949 (automotive-grade); ISO 14001 (environmental) is a plus. Ask for the actual certificates and check the issuing body, scope, and validity dates.
3. Quality documentation
A capable supplier routinely provides material certificates, first-article inspection (FAI), and test reports — pressure, leak, salt-spray, and dimensional. If they can't, that's a warning sign.
4. Samples and prototyping
Are they willing to produce a sample before mass production? A sample stage protects you — it verifies fit and quality before you commit to volume.
5. Communication and language
Direct, responsive, English-capable communication — ideally with engineers, not only sales — prevents costly misunderstandings on custom work.
6. Track record
Years in business, the industries and customers they serve, and consistency across repeat orders all indicate reliability.
Red flags
- Won't share certificates or test reports
- Evasive about in-house manufacturing
- Pushes you to skip samples
- Price dramatically below everyone else
Frequently asked questions
How do I confirm a certificate is genuine?
Check the issuing body, scope, and dates, and verify it with the certification body.
Manufacturer or trading company — does it matter?
For custom parts, dealing directly with the manufacturer usually gives better quality and communication.
Is the cheapest supplier a bad sign?
A price far below the market often means lower-grade material or skipped quality steps.
Related reading
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