Prototype into first year of production
Start on compression. It's cheap to tool, forgiving of design change, and produces real parts. If volume grows into LSR territory, migrate.
Silicone manufacturing guide
Compression, injection or LSR — which route fits your part?
Three routes, one part, one honest answer. This is the conversation we have with almost every OEM customer on the first call. Here it is written down, without the marketing overlay.
TL;DR
Compression up to a point, LSR above it, injection where the material family says so.
For most silicone and rubber parts below roughly twenty thousand a year, compression moulding gives the right unit cost against sensible tooling. Above that threshold, LSR starts to win on cycle time and finish quality even accounting for higher tooling cost.
Solid silicone injection (HCR) occupies a narrower band: parts where you need injection speed and consistency but the material family for the application isn't compatible with LSR. Less common than either of the other two, but the right answer where it fits.
The threshold isn't a fixed number. Part geometry, material grade, finish requirements, and how tolerant the design is of a witness line all move it. What follows is the shape of the conversation we have when working out where a specific part actually lands.
Start here
How annual volume shapes the route.
The most useful single question at enquiry stage is: how many parts a year, honestly, for how many years?
Under 1,000 a year
Almost always compression, often on shared tooling. LSR tooling investment doesn't recover in a lifetime at this volume.
1,000 to 20,000 a year
Compression is usually right. Multi-cavity as volume grows. LSR only if the finish or cycle-time requirement demands it.
20,000 to 100,000 a year
The transition zone. LSR often wins on total cost once you factor in finishing and reject rate. We model both routes for parts in this range.
Over 100,000 a year
LSR by default for anything the material family supports. Cycle time and clean release become dominant.
Over 500,000 a year
LSR with high cavity counts and possibly automation. Tooling investment is significant but per-part cost drops accordingly.
The other axis
Not everything can be LSR.
Silicone (any durometer)
LSR covers the softer end; HCR (high-consistency silicone) covers the firmer end. Compression handles both.
EPDM, nitrile, natural rubber
Compression only. These material families are supplied as solid gum, not as liquid two-part systems.
Fluorosilicone and exotic grades
Compression usually, LSR occasionally. Availability of the grade in a liquid form varies by supplier.
The tie-breaker
Where the parting line can land.
For parts where a witness line matters — anything cosmetic, sealing-critical, or skin-contact — the route decision often comes down to where flash naturally forms.
Cosmetic or skin-contact parts
LSR cold-runner tooling can produce parts with essentially no visible flash. Compression always leaves something, however small.
Sealing-critical parts
LSR keeps the sealing lip clean. Compression can work with careful tool design that keeps the parting line off the sealing face.
Assembly-hidden parts
Compression is perfectly fine — flash lands on a face you never see. LSR is overkill and expensive.
High-precision internal features
LSR usually wins on repeatability of internal geometry. Compression is fine for external geometry.
The pattern
Four common OEM situations and our default answer.
Long-lived component, high volume
LSR from the start, provided the material family fits. The investment recovers across the life of the part.
Sealing part inside an electronic device
LSR almost always. Clean sealing face, batch traceability, electronics-compatible grades.
Rubber part for industrial equipment
Compression, in a compound suited to the application. LSR doesn't cover most industrial rubber grades.
Keep reading
More guides from the workshop.
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Read the guideSilicone, rubber and TPE — what each is good for
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Read the guideDesigning a part for volume from the start
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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.
Which route suits your quantity
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
TheodoreEmployee Welfare