Manufacturing services · Chapter A · Method 05

Transfer moulding

Rubber is loaded into a pot above a closed tool and forced through sprues into the cavities. Better control than compression for multi-cavity tools and parts with inserts.

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Vertical rubber moulding machine of the type used for injection-transfer moulding. Representative process photo · Guido Radig · CC BY 3.0 · Wikimedia Commons

How it works

Transfer moulding, step by step.

A labelled schematic of the process (not to scale), and the four steps every job goes through.

Labelled diagram showing how transfer moulding works — Schematic · not to scale. Drawn by TCI Group.

STEP 01

Load pot

Place a pre-form of compound in the transfer pot.

STEP 02

Transfer

A plunger pushes the softened rubber through sprues.

STEP 03

Cure

Hold heat and pressure until the parts cure.

STEP 04

Demould

Open, remove parts and the cull, then deflash.

Reference figures

What to expect.

Typical industry values to help you plan. We agree the figures for your part on the drawing.

ToleranceAgreed per toolSimilar to compression

CavitiesMulti-cavityClosed tool fills evenly

InsertsMetal & plasticBonded during cure

WastePot cull & spruesPer cycle

Materials	EPDM, NBR, FKM, natural rubber and HCR silicone; bonding agents for rubber-to-metal parts.
Finishes	As tool; minimal flash compared with compression because the tool is closed before filling.
Design guidance	Position sprues where gate marks are acceptable. Design positive location for inserts. Balance sprue lengths across cavities.
Best suited to	Small precision rubber parts, bonded rubber-to-metal components and multi-cavity seals.
Watch-outs	More material waste than compression; tooling is more complex.

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Reference figures are typical published industry values for planning, not a guarantee; final tolerances, materials and finishes are agreed in writing for each project.