Choose an injection mold manufacturer in China by verification, not by presentation: ask for the machine list, a written DFM report, the dimensional report from first article and a defined handover pack before you place the order. A supplier who cannot produce those four things is a broker with a website. Below are the seven checks we would want a buyer to run on us, each one followed by our own answer, so you can hold it against every other quote on your desk.
Key takeaways
- Ask for numbers with units, never adjectives. "Advanced equipment" cannot be checked; "13 CNC machining centres, travels up to 1,600 mm" can.
- Machining tolerance and molded part tolerance are two different figures. A supplier who gives you one number for both has not thought the question through.
- A DFM and moldflow study before steel is cut is the cheapest risk reduction in the whole project. Insist on it in writing.
- Lead time should be quoted as days to T1 sample, not days to shipment. The T1 date is the one your project actually turns on.
- Decide early whether you are buying from a pure tool maker or a factory that also runs production — the incentives differ, and so does who absorbs a trial that needs three attempts.
- Tool ownership, design data and spare parts should be settled in writing before the purchase order, not after a dispute.
- The handover pack at T1 is where good projects separate from cheap ones: samples, photos, video, process parameters and a measured dimensional report.
In this guide
- 1. Verify technical capability with a machine list, not adjectives
- 2. Insist on measured quality evidence
- 3. Test communication before you commit
- 4. Require DFM and moldflow before steel is cut
- 5. Get the whole cost in one document
- 6. Check who benefits from your production volume
- 7. Fix the handover before you place the order
- Put all seven checks in one email
The seven checks at a glance
The middle column is what a credible answer contains. The right-hand column is our answer, dated 2026 — use it as the benchmark when you read the replies you get back.
| Check | What a credible answer contains | Our answer (2026) |
|---|---|---|
| 1. Capability | Machine models and travels, EDM types, inspection equipment, plant area, production headcount | 13 CNC centres to 1,600 mm · 6 EDM incl. Sodick mirror-finish · 3 wire EDM · 5 grinders · CMM · 2,000 m² · 49 staff |
| 2. Quality evidence | Documented inspection points plus a measured report on critical dimensions | In-process checks, CMM report on critical dimensions, traceability by mold number |
| 3. Communication | A named engineer, technical questions in the first reply, a stated response time | 3 project engineers; English by email, phone and video; milestone updates with photos |
| 4. DFM before steel | A written report covering gate, filling, cooling, warp, draft and ejection | Modelled in UG, run through Moldflow, written report in 3 working days, no cost |
| 5. Cost structure | Every line item named: steel grade, base, hot runner brand, cavities, finish, trial, freight | Quoted line by line; 20–30 molds per month; T1 in 35 / 42 / 50 days by complexity |
| 6. Incentives | Who owns the tool, the design data and the spare parts, and who wants your volume | Mold making in-house; molding through vetted partners; tool and records transfer to you |
| 7. Handover | Samples, photos, video, process parameters, dimensional report, warranty terms | All five at T1, 12-month warranty, up to 1,000,000 shots depending on steel grade and maintenance |
1. Verify technical capability with a machine list, not adjectives
Machining capacity is the first thing worth verifying, because it is the difference between a tool maker and a broker. Every supplier describes itself as advanced, so the adjectives carry no information. Ask for the list instead:
- How many CNC machining centres, and what is the maximum travel on the largest one?
- How many EDM machines, and which types — sinker, wire, mirror-finish, twin-head?
- Which machine brands, and what condition are they in?
- What is the plant area, and how many people work in production?
- What inspection equipment is on site — a CMM, or only hand tools?
A supplier who answers these in numbers has a factory. One who answers with "a strong supply chain" is passing your job to somebody else, and you will pay a margin for the introduction. The travel figure matters more than most buyers expect: a tool that does not fit on the largest machine is subcontracted, and subcontracted machining is where tolerance and schedule both get away from you.
Our answer: 13 CNC machining centres with travels up to 1,600 mm, six EDM machines including Sodick mirror-finish and twin-head units, three wire EDMs and five surface grinders, with Makino and Sodick as our main machine brands. Dimensional inspection runs on CMM in-house. The largest tool we build in-house measures 1,600 × 1,000 × 500 mm and weighs up to 15 t, with cavity counts up to 48. The plant covers 2,000 m², staffed by 49 people — 37 in production and 12 in the office. We have delivered more than 1,500 molds since 2015, for automotive, electronics, industrial and medical customers across North America and Europe.
2. Insist on measured quality evidence
A quality document tells you that a process existed on the day it was audited. Measured data tells you what actually happened to your tool. Ask for the evidence that is specific to your job:
- Which dimensions are checked at first article, and with what instrument?
- Do you receive a dimensional report, or a photograph of a sample?
- Is inspection done during machining, or only at the end?
- Can a specific tool be traced back to its steel grade documentation, its electrodes and its machining records?
What you are testing for is whether quality is a system or a final gate. A shop that checks only at the end finds problems when they are expensive to fix. One that checks during machining finds them when they are cheap to fix. If your programme requires a formally audited quality system as a contractual condition, raise it in the first exchange rather than after the purchase order — that saves both sides a wasted month.
Our answer: the workflow is documented rather than decorative. Incoming steel is verified by grade and hardness before it is cut. Core and cavity inserts are checked during machining, not after. First article produces a CMM dimensional report on the critical dimensions, and every tool stays traceable by mold number through steel, electrodes, machining and trial. On precision we quote two figures and keep them apart: machining tolerance of ±0.005 mm on critical mold dimensions, which is what the Sodick mirror-finish EDM and the CMM verification are there to deliver, and molded part tolerance of ±0.01 mm on critical dimensions, subject to the resin and the part geometry. Where a drawing calls for it, we also supply the measured cycle and process data so your quality team can sign off from numbers instead of a sample in a box.
3. Test communication before you commit
Remote tooling projects fail on communication more often than on machining. You can test this in the first two emails, before any money moves:
- Did they ask engineering questions about your part, or quote immediately?
- Is your contact an engineer, or a salesperson passing messages?
- Can they hold a technical conversation by phone or video, not only by email?
- What is the update rhythm during the build, and who owns it?
A quote that arrives in two hours with no questions is not efficiency. It means nobody read the geometry, and the assumptions they made will surface later as change orders.
Our answer: three project engineers. Your project engineer handles English directly by email, phone and video, and is the person who signs the DFM report your tool is built from — so the engineering decisions do not get translated twice. Milestone updates with photographs are issued at design approval, steel cutting, electrode production, assembly, trial and packing, rather than only when you ask.
4. Require DFM and moldflow before steel is cut
Design for manufacturing is not a formality, and it is not an upsell. It is the last moment at which a problem costs a few hours instead of a few weeks.
- Does the DFM arrive before the quote is finalised, or after the purchase order?
- Is it a written report, or a reassuring phone call?
- Does it include filling, packing, cooling and warp simulation, or just a draft-angle check?
- If it requires a design change from you, who carries the cost of that change?
Some of the most expensive defects in plastic parts are decided before any metal is cut: a gate in the wrong place, cooling that creates a warp you cannot dial out, a wall section that sinks. Simulation is cheap compared with a welded-and-remachined cavity.
Our answer: your STEP or IGES file is modelled in UG, run through Moldflow, and returned as a written DFM report within 3 working days at no cost, before the tool is quoted in final form. The report covers gate location and type, fill and pressure balance, weld lines and air traps, cooling layout, warp prediction, draft, wall thickness against the material, ejection, and the tolerance stack on the dimensions you flagged. Each point carries a recommendation, and where we disagree with the drawing we say why rather than quoting around it. Our DFM process and mold design and DFM guide show the full workflow.
5. Get the whole cost in one document
Ask for the quote line by line, and check that all of it is named:
- Cavity and core steel grade, stated in a standard you recognise
- Mold base brand, and whether the hot runner is branded or generic
- Number of cavities, cooling layout, and the SPI finish grade on each surface
- Sliders, lifters and any secondary operation
- Trial material, spare inserts, packing, and freight
- What a design change costs after approval
A quote that comes in 40% below the others is not a bargain. It is usually a steel grade you have not been told about, and you will meet that grade again as a weld repair in year two. Our full cost breakdown shows what each of those lines is worth.
Our answer: we quote line by line and state the steel in European DIN terms — 1.2344 (H13) and 1.2343 (H11) hardened to 48–52 HRC for high-volume tools, 1.2738HH pre-hardened at 30–34 HRC for medium volumes, S136 for corrosive resins, P20 for short runs, and ESR grades where insert life matters. Bases are LKM, DME or HASCO; hot runners come from HRS, Yudo, Husky, Incoe or Mold-Masters. We build 20–30 molds per month, with lead time to T1 sample of 35 days for a simple tool, 42 for medium and 50 for complex, and 30 days as the floor when the design is frozen and components are in stock.
6. Check who benefits from your production volume
Ask a direct question: does the tool maker also want to run your production? There is nothing wrong with either answer, but the incentives differ in ways that affect your project.
- A factory that also molds may price the tool keenly and recover the margin on production — which is fine until your tool waits behind their own contracts at trial time, or until the tool is built around their preferred machine rather than your chosen supplier’s.
- A pure tool maker has no volume to protect, but may have no view on whether the design actually molds well at your target cycle time.
- The third model, and the one we use, is a tool maker with molding partners: the tool is made in-house and run through vetted factories, so the incentive ends with a tool that hits specification.
Whoever you choose, settle ownership in writing. Who holds the tool, the mold design data, the spare parts and the right to move the tool to another molder should be clear before the purchase order, not after a dispute. Our FAQ on tool ownership and IP transfer covers the clauses worth insisting on.
Our answer: we make molds in-house and run trials and production through vetted partner factories, which means our incentive ends with a tool that runs to specification rather than with a volume commitment you did not ask for. Prototypes and small batches are available through those partners. You are free to mold anywhere you choose — the tool design, the process parameters and the dimensional records are documented so that another molder can pick the tool up without starting again.
7. Fix the handover before you place the order
The handover is where a cheap tool reveals itself. Agree the list in advance, so that "we sent samples" cannot substitute for data:
- Trial samples, photographed, with the process sheet they were made under
- A video of the trial run, so you can see the ejection and the cycle
- A dimensional report on the critical dimensions, measured on a CMM
- A spare parts list — ejection pins, sprue bush, hot runner components
- Warranty terms, and an honest statement of expected tool life with its conditions
Our answer: the trial pack is samples, trial photos, a trial video, the full process parameter sheet and a CMM dimensional report on the critical dimensions. Tools carry a 12-month warranty. On tool life we state the condition as well as the number: up to 1,000,000 shots, depending on steel grade and maintenance — which in practice means hardened hot-work steels such as 1.2344 or 1.2343 and a sensible maintenance interval. If a supplier quotes a shot count without conditions, ask what it is contingent on; the answer is usually "nothing", and that is not an answer.
Put all seven checks in one email
Here is the whole list as a single message you can send to any supplier, including us. Fill in the blanks, send the same text to every candidate, and compare the replies side by side.
- Capability: please send your machine list — CNC count with maximum travel, EDM types, wire EDM, inspection equipment — plus plant area and production headcount.
- Quality: which dimensions do you measure at first article, with what instrument, and in what report format? Please attach a sample report from a recent job.
- Contact: who is my project engineer, what is your typical response time, and can we hold a technical call before quoting?
- DFM: do you provide a written DFM and moldflow report before the final quote, at what cost, and in how many working days?
- Cost: please quote line by line — steel grade and hardness, mold base brand, hot runner brand, cavity count, cooling design, SPI finish, sliding actions, trial material, packing and freight.
- Timeline: days to T1 sample and days to shipment for my part, and what would have to change to shorten it.
- Ownership: after final payment, who owns the tool, the mold design data and the spare parts, and can the tool be moved to another molder?
- Handover: what exactly do I receive at T1 — samples, photos, video, process parameter sheet, dimensional report?
A supplier who answers all eight in numbers is worth a second call. One who answers three of them is quoting a job they intend to sub-contract, and you should price that risk into the decision.
Where our numbers come from
Every figure on this page comes from our own shop records and is dated 2026. We publish them because a buyer 8,000 km away cannot walk the floor, and because a number you can check is worth more than an adjective you have to trust. When something changes — a machine added, a headcount moved — we update this page rather than leaving the older, friendlier figure in place.
The same logic runs through the rest of this library: the mold cost breakdown shows where the money goes line by line, and how tight injection molding tolerances can actually be puts machining tolerance and part tolerance in their proper places.
Compare us against this list
Send us the drawing and the annual volume, and we will answer all eight points in writing, with the DFM report inside three working days and no cost. Ask an engineer — a project engineer, not a sales desk.
Related guides in this series
This article is part of our Sourcing Injection Molds from China — a full walkthrough of the topic with the numbers and checklists behind each decision.