Consumer product with soft-touch grip
2K if volume is over 50k a year; overmoulding if lower. Bonded rarely — the interface shows.
Silicone manufacturing guide
Overmoulding: when it saves you a step, and when it doesn't.
Overmoulding, two-shot, and bonded assembly are all ways to end up with a silicone part attached to a rigid substrate. Each has a case; each has a price. This is the conversation we have with OEMs before the tool is drawn.
The setup
You have two materials that need to be joined. The question is where the join happens.
Three routes get you to a rigid substrate with silicone bonded onto it. The alternatives all produce similar-looking parts; they cost different amounts and behave differently in the field.
Overmoulding takes a pre-made substrate, loads it into a silicone moulding tool, and moulds silicone around it. Bond formed during silicone cure. One press cycle, one supplier, one part number.
Two-shot (2K) moulding moulds both materials in the same tool on the same press in one cycle. Substrate injected first, tool rotates, silicone injected onto it. Higher tooling investment; stronger bond; higher throughput on suitable geometry.
Bonded assembly — mould the two parts separately, glue them together afterwards. Cheapest tooling investment, most process steps, weakest interface at the bond line.
The default choice
Where standard overmoulding wins.
Overmoulding as a separate operation is the most common OEM route because it fits volumes and complexities where 2K would be overkill.
Moderate volumes
A few thousand to tens of thousands a year. 2K tooling investment doesn't recover; bonded assembly labour costs more over the run.
Substrate you already produce
You already have a plastic housing supply. Overmoulding adds silicone onto your existing part without redesigning the substrate.
Substrate that changes across SKUs
Same silicone geometry across multiple substrate variants. Standard overmoulding handles this cleanly; 2K would require multiple base tools.
Mid-programme validation still possible
You want to prove the assembly at real volume without committing to full 2K tooling investment. Overmoulding lets you validate cheaply, migrate later.
The higher-volume answer
Three situations where two-shot moulding earns its cost.
High volume, stable design
Above roughly fifty thousand a year with a stable design, 2K cycle time savings offset the extra tooling investment.
Bond needs to be exceptional
2K bonds are formed under ideal conditions — substrate still hot, still perfectly located. On parts where bond integrity is critical, 2K wins.
Manual handling is the bottleneck
If loading substrates by hand into an overmould tool is your cycle-time constraint, 2K removes that step entirely.
The right answer sometimes
Three cases where separate parts and glue win.
Very low volume
Under a few thousand a year, no bond justifies moulding investment. Assemble by hand or with cell fixtures.
Substrate can't survive moulding
Some substrates — thin PCBs, sensitive electronics assemblies — can't tolerate the heat or clamping of an overmould cycle.
Bond can be non-permanent
If the interface is designed to be serviceable — the silicone part might be replaced during the product's life — bonded assembly with a defeatable adhesive is better than a moulded-in bond.
In practice
Four common OEM scenarios.
Medical device with integrated seal
Overmoulding usually. 2K if the seal is critical enough that the extra bond integrity justifies the tooling investment.
Electronics enclosure with gasket
Overmoulding for most; bonded assembly if the enclosure design allows a serviceable seal.
Industrial tool handle
Overmoulding — tolerates modest volumes cleanly, no need for 2K sophistication.
Keep reading
More guides from the workshop.
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Read the guidePost-processing silicone — what happens after the press opens
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Read the guideDesigned and developed in the UK. UK moulding capability, with some higher-volume production placed with trusted partners where that's the right commercial answer.
At a glance
The idea in a picture.
How overmoulding works
Swipe to see the whole diagram
Get in touch
Tell us the part, the volume, and the timeline.
Rough annual volume, target unit price, and any deadlines. That's enough to work out whether compression, LSR injection or something else is the right tool.
Real people, a real workshop
You deal with the people who make it.
No call centre and no middlemen. When you contact TCI Products, you speak to the team who design, build and check your mould.
- A real Warwickshire workshopUnit 15, Waterloo Park, Bidford-on-Avon, Alcester B50 4JG.
- Real people on the phoneCall the team on 01789 224228, Monday to Friday.
- The same team on every jobDesign, production and aftercare come from the people you see here.
- Part of TCI GroupFive specialist brands, one engineering team. Visit TCI Group.
Thomas LaneManaging Director
George PrestonDesign & Project Manager
Kelly BallingerHead of Partnerships
Jim AndertonProduction Manager
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