Spec the finish you can see, not the finish you can measure
A finish tolerance no human eye can detect adds cost with no benefit. Spec what a customer will notice.
Manufacturing guide for OEM buyers
Post-processing silicone — what happens after the press opens.
A moulded part isn't always a finished part. Understanding what happens between the press and the shipment helps you specify the finish you actually need, and stops you paying for finish you don't.
The starting point
Almost every moulded part needs some finishing.
Even on a well-designed LSR tool with a cold runner, some parts come off the press with a small sprue, a gate witness, or a light flash line. On compression tools, flash is more or less always present — it's how the process works.
The question isn't whether finishing happens, it's how much, and whether it's done at the moulder or at your end. Both are valid. Getting it done at the moulder collapses the paperwork and catches defects earlier; getting it done at your end lets you inspect against your own criteria.
This guide covers the finishing operations we run in-house — cryogenic tumble deflash, hand deflash, secondary trim, printing, coating and inspection — and how to specify them without over- or under-buying.
Removing flash
How we get flash off, and when.
There are three main deflash routes. Which one fits depends on the part, the volume, and the finish criteria.
Cryogenic tumble deflash
Parts are cooled below the glass transition of the flash and tumbled with plastic media. Flash breaks off cleanly; the part body is unaffected. Best for high-volume small parts with acceptable cosmetic tolerance for a slight witness.
Hand deflash
Operator trims flash with a blade or scissors under magnification. Slow but precise. Best for parts with cosmetic or sealing-critical faces where a witness line isn't acceptable.
Secondary die trim
A dedicated cutter blade or fixture removes specific flash features on a defined path. Best for parts with repetitive flash geometry — sealing lips, membrane rings — at moderate volume.
Inline flash removal
On some LSR tools, the ejector plate or a stripper mechanism removes the runner during ejection. No secondary operation needed. Best for high-volume parts designed for it from the start.
Combination approach
Most real programmes use two routes — cryo for bulk deflash, hand-finish on cosmetic faces. We'll spec the combination that hits your finish criteria for the least cost.
Post-mould inspection
Three inspection layers that get built in.
First-off against golden sample
First parts from every run compared to the signed-off golden sample. Any drift raised before the run continues.
Dimensional check on defined features
Not every dimension gets measured on every part — that would double the cost. Critical-to-function dimensions are checked on a defined sample rate.
Cosmetic under magnification
For visible or skin-contact parts, cosmetic acceptance criteria applied under magnification. Signed off against the golden sample and any photographic reference.
Adding features after moulding
Four decoration options.
Sometimes the finish involves more than just cleaning the part up. Here's what we run in-house.
Pad printing
Silicone-compatible inks pad-printed onto the moulded surface. Standard for graphics, logos, and small decorative features.
Laser marking
Laser marks the silicone surface directly. Permanent, no ink. Best for permanent codes, serial numbers, batch traceability.
Coating for wear or feel
UV-cured or thermal-cured coating applied for scratch resistance, matte finish, or specific tactile properties. Applied on defined parts of the surface.
Colouring in the mould
Colour matched in the material batch itself. Not a post-process, but often confused with one. Colour is locked at material spec, not applied later.
In practice
Four principles for finish specification.
Different faces get different criteria
The face that's visible and the face that's hidden don't need the same finish. Spec each separately in the drawing.
Provide a golden sample early
A physical reference is worth more than any drawing note. Spec the finish by comparison to it.
Distinguish critical from cosmetic
Sealing faces are critical, cosmetic faces are cosmetic. Inspection criteria and reject rules follow that split.
Keep reading
More guides from the workshop.
Colour matching and batch consistency
For anything a customer will see, colour is one of the two things they judge (feel is the other). Getting the colour right is…
Read the guideMoving from prototype tooling to production
Your product is real. You've made prototypes, maybe pilot runs. The design is stable and the volume forecast is starting to be…
Read the guideChoosing a Shore hardness for your silicone part
Shore A is the number that appears on nearly every silicone drawing and is understood by almost nobody outside the rubber trade.…
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.
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