Most guides to manufacturing in China are written by people who buy from factories. This one is written by someone who runs them.
That changes what's worth telling you. The advice you usually get — get multiple quotes, visit the factory, use an escrow — isn't wrong, it's just downstream of where the money is actually lost. In thirty years I've watched founders lose $40,000, $80,000, once $134,000, and almost none of it happened because they picked a dishonest supplier. It happened because of decisions made weeks earlier, by people who didn't know they were making them.
This guide follows that sequence: design, supplier selection, quoting, contracting, production, quality. Each section links to a longer piece where there's more to say.
1. Design decisions cost more than supplier decisions
By the time a drawing reaches a factory for quoting, the geometry is frozen, the material is locked, and the cheap changes are gone. Everything the factory can do at that point is priced around a design it had no part in shaping.
Three examples of decisions that look free in CAD and expensive in steel:
Wall thickness transitions. A 0.8mm wall next to a 4mm boss reads as a small geometric detail on screen. At production speed it's a process decision: the thin section can start freezing before it fills, while the thick section shrinks last and pulls porosity toward itself. One factory caught exactly this before cutting steel and saved a client $38,000.
Draft angle. Every surface parallel to the direction the tool opens needs a taper so the part can release. Adding it in CAD takes minutes. Adding it after the tool is designed means re-machining cavity and core, re-checking parting lines, and re-verifying wall thickness. That's what a "design revision" line item on a mold quote usually is.
Tolerance stack-up. Three features each held to ±0.10mm, all referencing the same datum, can put a part 0.3mm off nominal while every individual dimension measures in spec. Parts pass inspection and won't assemble.
What to do: before a drawing leaves your hands, someone who has actually made the part should look at it — a machinist, a tooling engineer, or your factory if they'll do it honestly. Twenty minutes of that conversation is worth more than any standard you'll read.
2. Choosing a factory: screen on behaviour, not credentials
Certifications tell you a factory can pass an audit. They don't tell you whether it will catch your mistakes.
The most useful screening test costs nothing: send the same RFQ to three or four candidates, leave one genuine ambiguity in the drawing, and see who asks about it.
- A factory that asks "what does this part do?" or "why is this wall so thin?" has opened your files.
- A factory that returns a fast price with no questions will build exactly what you drew — mistakes included — and invoice before the problems appear.
The second kind isn't dishonest. It's doing precisely what was asked. But the fastest quote is usually the one that didn't ask a single question, and in casting that's frequently the most expensive outcome there is.
One question is worth asking every candidate before you commit: "What DFM issues do you see in this design?" A supplier that has reviewed the files names something specific. One that just wants the order says "design looks fine, no issues" — which on a first-pass review is almost always wrong.
3. Reading a mold quote
A mold quote isn't a price. It's a specification in disguise, and two quotes with the same number can describe completely different products.
The variables that move the figure most:
| Variable | Why it changes the price |
|---|---|
| Steel grade and tier | Domestic P20 is ~¥5.9/kg; imported ASSAB S136 is ¥60–80/kg. "P20" alone is not a spec. |
| Cavity count | More cavities cost more tool and less per part. The right number depends on your real annual volume. |
| Expected tool life | An aluminum die typically runs 50,000–100,000 shots before weld repair and re-cutting. A tool quoted for 50,000 shots against a 180,000/year forecast is the expensive option. |
| Surface finish / texture | Polish grade and texture drive both tooling hours and required draft angle. |
| Side actions and undercuts | Each one adds mechanism, maintenance and failure modes. |
| Trial and revision allowance | How many T-samples are included before revisions become chargeable. |
Current figures for steel, machine rates and casting metal are in the China Manufacturing Cost Index, updated quarterly from our own procurement records.
4. Tooling ownership: settle it before the deposit
Paying for a tool does not automatically give you the right to remove it.
The contract needs to state, explicitly: that the buyer owns the tooling; that it will be released on request; where it is physically stored; and what happens to it if the relationship ends. If the agreement is silent on any of these, assume a dispute is possible.
Settle this before the deposit is paid. Leverage exists only while money is still owed.
5. Payment terms: the trigger matters more than the percentage
These are the terms we use in our own factories:
- Tooling, option A: 50% deposit / 50% on part approval
- Tooling, option B: 40% deposit / 30% after first trial samples (T1) / 30% on sample approval
- Production: 50% deposit / 50% on inspection passed, before shipment
For a first tool, option B is the one to ask for: it ties money to two physical events — samples in your hand, then samples you've approved — instead of dates on a calendar.
On production, the words that matter are the last four. "50% on inspection passed, before shipment" and "50% at shipment" look almost identical on a purchase order and are not the same document. The first keeps the factory's last mile — the QC nobody watches, the packing nobody checks — inside the scope of getting paid. The second makes it your problem after the money is gone.
This drift is how experienced founders get caught: after a few clean runs, "we've never had an issue" quietly becomes a payment term.
6. Quality: what inspection does and doesn't catch
Dimensional inspection measures the outside of a part. A significant class of defects lives inside it.
Porosity in a die casting passes visual inspection and passes dimensional inspection, then appears when the part is machined, pressure tested, plated, or loaded in service. It's driven by process conditions — machine, shot profile, die temperature, cycle time — more than by geometry, which is why a proven tool moved to a different factory can produce failing parts with no change to the steel. That's how a $0.80-per-part saving became a $134,000 loss.
Two practices prevent most of it:
- Write down the acceptance criteria, including internal quality. If porosity limits, pressure test or section criteria aren't specified, they aren't being checked.
- Don't skip the pilot run. Prototype, small validation batch, pre-production run, then mass production. Each stage exists to catch what the previous one missed. Skipping from prototype to full volume means paying for the missing steps at production price.
7. Moving a tool to a new supplier
The tool defines geometry. Quality is produced by the tool and the process together — and the process stays behind: machine tonnage, shot profile, die temperature control, cycle time, spray routine, alloy chemistry, and the operator who knows the tool's quirks.
A tool moved without its process is a new process on known geometry. Treat the move as a qualification: get the parameters, send the full acceptance criteria, run trial shots and inspect them properly, run a pilot batch, and keep the incumbent running until the new source passes.
Then do the arithmetic honestly. The comparison isn't "$0.80 per part versus zero" — it's "$0.80 per part versus the cost of one bad run."
8. What things actually cost right now
We publish our own procurement prices once a quarter so founders have a reference to check quotes against. Highlights from Q3 2026:
- Domestic P20 mold steel ¥5.9/kg (down ~15% vs Q2); imported ASSAB S136 ¥60–80/kg (flat)
- Aluminum ADC12 ingot ¥23,900–24,100/ton (up ~3%)
- Zinc Zamak 3 ingot ¥24,905–25,005/ton (down ~1%)
- Injection molding machine rates ¥80–500+/hour depending on tonnage
Full tables, quarter-over-quarter movement and interpretation: the China Manufacturing Cost Index.
The short version
- Get someone who has made the part to review the drawing before it's released.
- Screen factories on whether they ask questions, not on certifications.
- Treat a mold quote as a specification — ask which steel tier, how many cavities, what tool life.
- Put tooling ownership in writing before the deposit.
- Tie the final payment to inspection passed, not to shipment.
- Specify internal quality criteria, and don't skip the pilot run.
- Price a supplier switch against the cost of one bad batch, not against zero.