Manufacturing services · Chapter B · Method 11

Overmoulding

A second material, usually a soft TPE or silicone, is moulded over a rigid substrate to add grip, sealing or colour in one part.

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Two-shot moulded keycaps: a second material moulded through the first. Representative process photo · WeissEtwas · free use · Wikimedia Commons

How it works

Overmoulding, step by step.

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

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

STEP 01

Substrate

Mould or supply the rigid first part.

STEP 02

Transfer

Move it into the second tool or rotate the platen.

STEP 03

Second shot

Inject the soft material over the substrate.

STEP 04

Bond check

Eject and check adhesion and appearance.

Reference figures

What to expect.

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

ToleranceAs injection toolPer shot

HardnessShore A 30–80Typical soft-touch

BondChemical or mechanicalMaterial pair dependent

VolumeMedium – highTwo-shot or pick-and-place

Materials	Rigid PP, ABS, PC, PA substrates; TPE, TPU and LSR overmould materials chosen for compatibility.
Finishes	Contrasting colours and textures; matte soft-touch grips over gloss substrates.
Design guidance	Pick compatible material pairs, or add mechanical locks. Keep soft-material walls even and not too thin. Design shut-offs so the second shot stops cleanly.
Best suited to	Tool and appliance handles, seals on housings, wearable devices and kitchen utensils.
Watch-outs	Two tools or a two-shot press; adhesion must be proven by test.

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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.