Manufacturing services · Chapter B · Method 10

Insert moulding

A metal or plastic insert is placed in the tool and plastic is moulded around it, giving a single bonded part with no secondary assembly.

Ask about this method All Plastics & polyurethane methods

Electrofusion pipe coupling: an embedded heating wire moulded into the fitting. Representative process photo · XlaDen · CC BY-SA 4.0 · Wikimedia Commons

Production injection tool with cooling lines. Representative process photo · MobiusDaXter · CC BY-SA 3.0 · Wikimedia Commons

How it works

Insert 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 insert moulding works — Schematic · not to scale. Drawn by TCI Group.

STEP 01

Load insert

Place threaded bushes, pins or wire in the cavity.

STEP 02

Close

The tool closes and locates the insert.

STEP 03

Inject

Plastic flows around and locks the insert.

STEP 04

Eject & check

Eject and check insert position and pull-out.

Reference figures

What to expect.

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

ToleranceAs injection tool±0.13 mm + shrink

InsertsMetal, plastic, wireLocated in tool

LoadingManual or robotVolume dependent

StrengthHigh pull-outKnurled inserts

Materials	Brass and steel threaded inserts, pins, electrical contacts; host plastics such as PA, PBT, PP and PC.
Finishes	As injection moulding; inserts can be pre-plated.
Design guidance	Use knurls, grooves or holes to key the insert. Leave enough plastic around the insert to avoid cracking. Allow for insert stock tolerance in the tool.
Best suited to	Threaded housings, electrical connectors, handles and pipe fittings.
Watch-outs	Insert loading adds cycle time; mixed materials complicate recycling.

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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.