Sourcing an injection mold in China: a 12-point checklist

Stage 1 — Before you request quotations

1. Fix your own specification first

Resin grade (with filler), annual volume, target cycle, cosmetic requirement, tolerance-critical dimensions, packaging, market and compliance needs. A supplier cannot quote a tool for a product they cannot see. Sending a complete package is the single fastest way to shorten a quotation cycle — and it makes quotes comparable.

2. Decide the scope explicitly

Mold only, or mold plus molded parts? Design support included? Hot runner included? Texture included? Who buys the hot runner controller? Vague scope is the most common origin of a “surprise” price increase later.

Stage 2 — Qualifying the supplier

3. Ask for the machine list — with models and quantities

A capable toolmaker will send it in minutes. Then ask the follow-up question: which of the mold’s processes are subcontracted? If wire cutting, EDM or polishing go out, the supplier’s quoted lead time contains a queue they do not control.

4. Require a written DFM report with the quotation

Wall thickness, draft, undercuts, gating, cooling, shrinkage, tolerance realism. A supplier who only sends a price is asking you to discover the risks at T1, when every fix has a cost and a schedule impact.

5. Verify measurement capability

“We measure everything” means nothing without equipment. Ask which CMM, what accuracy, and request a sample dimensional report — redact the customer name if the supplier requires it. If the answer is “calipers”, the tolerance in the contract should match what calipers can prove.

6. Ask for a trial process, not a trial promise

Who runs T1, on which press, and what will you receive? The acceptable answer is: sample parts, a dimensional report referenced to your drawing, mold-running video and the process parameters. Anything less leaves you approving a mold you cannot see.

Stage 3 — Contract and payment

7. Write the technical annexe into the contract

The annexe should name cavity count, steel grades for cavity/core/slides, hot runner brand and type, finish class, standard components, the documentation pack, and the number of correction rounds included after T1. This converts “as discussed” into something enforceable.

8. Fix tool ownership in writing

State that the mold, its drawings and its data belong to you on final payment, and that the supplier will hand over all documentation and spare parts. This clause is what makes a supplier transfer possible later — and its absence is what makes some buyers captive.

9. Tie payments to verifiable milestones

A workable structure: deposit at order confirmation, and the balance against pre-shipment evidence — sample approval, dimensional report, photos and video of the packed tool. For long projects, add a milestone at design approval and at T1.

10. Agree the change-control mechanism

Who pays for a design change after approval? What happens if the customer changes the part, the resin or the finish class mid-project? A simple written rule (“changes are quoted with cost and schedule impact, and require written approval”) prevents most arguments.

Stage 4 — Delivery and after delivery

11. Inspect before shipment, not after arrival

Require photos of the tool and the packed case, the final dimensional data and the case list. Release the balance against those, not against a promise that shipping will follow. If you can visit or arrange a third-party inspection, do it — it is cheaper than a return shipment.

12. Receive the full documentation pack

2D and 3D drawings, plate and mechanism drawings, water-circuit and hot-runner documentation, steel and component certificates, the running-parameter sheet, the dimensional report and the spare-part set. Then file it where your production team can find it — a tool without documentation becomes a tool nobody wants to run.

Red flags worth taking seriously

• A price that comes in far below the field with no explanation of what changed.
• Reluctance to provide a machine list or to say what is subcontracted.
• Design approval that is a verbal WhatsApp message rather than an approved drawing revision.
• Trials reported as “good” without measured data or video.
• No spare-part list, no running-parameter sheet, no water-circuit diagram.
• Pressure to pay the balance before you have seen the packed tool.

How this checklist maps to working with CENTS

All twelve points are our standard practice: DFM report with every quotation, 36-machine list published with models and accuracy, all machining in-house, CMM-verified trials with sample parts and reports, tool ownership and documentation handover in the contract, and photos before shipment. If your procurement process needs a specific clause, form or certification stated in writing, send it at the RFQ stage — we would rather confirm what we can do in writing before you commit tooling budget than negotiate it afterwards.