Custom Injection Molding Services in China (OEM/ODM)

What a Molder Actually Needs From You

Moulders quote badly when the enquiry is vague, and a bad quote costs you weeks. A workable RFQ for custom molding contains: a 3D model in STEP and a 2D drawing with tolerances, the resin or the properties it must meet, the annual and first-order volume, the surface and colour requirement, the compliance market, and the target date the parts are needed in your warehouse. Nothing else is strictly required, and everything else you add helps.

Design Review: The Step That Saves the Most Money

A DFM review before the tool is cut is the highest-return hour in the whole project. The moulder should return the model marked with the problems it can see:

Wall thickness — uniform walls with a gradual transition; abrupt changes create sink marks and internal stress.
Draft angle — texture demands more draft than a polished surface, and missing draft means the part drags and scuffs on ejection.
Ribs and bosses — rib thickness relative to wall, boss wall thickness, and whether the boss needs a support or a coring change.
Gate position — which decides weld line location, flow length and whether a cosmetic surface is even achievable.
Undercuts — each one may need a slider or lifter, which adds tool cost and maintenance.
Shrinkage — every resin shrinks differently, and glass-filled grades shrink anisotropically. This is why the material must be fixed before the tool is cut.

Choosing Between Tooling Options

Option	Steel / build	Typical use
Prototype or bridge tool	Aluminium or soft steel, single cavity	Design validation, small series, market test
Production tool	P20, 718H, 2738 pre-hardened steel	General consumer and industrial parts
High-polish or transparent	S136, 1.2316, or equivalent	Lenses, cosmetic surfaces, PC parts
High-volume or abrasive resin	H13, 1.2344, hardened inserts	Glass-filled grades, long runs

Tool life is not a single number. A soft tool run outside its intended volume wears, flashes and then produces parts out of tolerance — and by that point the tool cost has already been capitalised into your unit price.

From Sample to Serial Production

The sequence a competent moulder will follow is: T1 trial and sample measurement, correction, T2 trial, dimensional report against the drawing, approval of the sample by the buyer, then production. Ask for a first-article inspection report that lists every drawing dimension with the measured value, not a summary that says "within tolerance". If your industry requires it, ask for a PPAP package at the agreed level.

Frequently Asked Questions

How much does a custom injection mould cost?

There is no honest single figure, because cost follows cavity count, part size, steel grade, slider count and surface requirement. What you can do is make quotes comparable: give every supplier the same model, drawing, resin and volume, then ask each to quote the tool separately from the part price and to state the tool's expected life in shots.

Should the moulder or I choose the resin?

State the performance requirement and let the moulder propose grades, but keep the final approval. The moulder knows what runs well on its machines; you know what the part must survive in service. Both matter, and the choice must be locked before tooling starts.

What is the difference between T1 and a production sample?

T1 is the first trial from a new tool, used to find problems. A production sample comes after corrections and represents what serial production will actually deliver. Approving a T1 sample as if it were production is one of the most expensive mistakes in custom molding.

Can you produce parts to my existing tool?

Often yes, and it is usually the fastest route to a second source. The supplier needs the tool, the original drawing, and the process sheet if it exists. Shipping a tool between countries also means customs paperwork and a realistic assessment of the tool's condition before it leaves.