SERVICES
Liquid Silicone Rubber (LSR) Injection Molding
LSR delivers elastic, temperature-stable, and biocompatible parts that thermoplastics cannot. We run cold-runner LSR tooling for flash-free seals, gaskets, and medical components — and overmold silicone onto plastic and metal for sealed, soft-touch interfaces.
WHAT WE OFFER
What We Offer
HOW IT WORKS
From Inquiry to Delivery
Metering & mixing
The two liquid components are metered 1:1 and mixed in a static mixer on the machine. The mix stays liquid at room temperature, so the whole feed system runs cold.
Injection through a cold runner
The mixed silicone is injected at low pressure through a cold-runner manifold — the material only cures where it must, keeping waste to a minimum and flash near zero.
Vulcanization in the heated mold
The mold is held at 120–180 °C. The platinum catalyst cross-links the silicone; cure time scales with wall thickness, from seconds on thin seals to a couple of minutes on thick sections.
Cooling and ejection
The part is ejected hot but dimensionally stable. Mold design must allow demolding without tearing the soft, elastic part.
Deflashing & optional post-cure
Automated deflashing removes any vestigial flash. Post-cure can be run where full physical property development or medical validation requires it.
CHALLENGES
Challenges This Service Solves
FAQ
Liquid Silicone Rubber (LSR) Injection Molding — FAQ
What hardness range can you mold?
Our standard window is 40–70 Shore A, with 10–80 A available — the right hardness is set by sealing force and tactile requirements.
How long is an LSR cycle?
Cure time scales with wall thickness — seconds for thin seals, a couple of minutes for thick sections. Cycle planning happens in DFM against your geometry.
Can LSR be overmolded onto plastic or metal?
Yes — PC+LSR and PPS+VMQ are standard combinations we run, plus metal inserts for sealed electronic assemblies.
Do you support medical validation?
Yes — ISO 13485 process control, ISO 10993 / USP Class VI capable grades, lot traceability and sterilization-ready handling.
What tooling lead time should I plan for?
The same in-house track as plastic tooling: rapid tools 7–12 days, production tools 25–30 days (45 for automotive-grade).
Is flash really eliminated?
Cold-runner tooling plus tight shut-off gets flash down to near zero — that is why LSR seals and gaskets are molded, not trimmed.
RELATED SEARCHES
What Buyers Search
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LSR Capabilities
Platinum-cure silicone, documented process windows, and clean-controlled molding.
Liquid Silicone Rubber (LSR) Molding
Two-component platinum-cure silicone injected into heated molds — flash-free, biocompatible parts for seals, gaskets and medical components.
- Cold-runner tooling (zero flash)
- 40–70 Shore A range
- Medical & food-grade LSR
- Automated deflashing
LSR Overmolding
Silicone molded over a plastic or metal substrate for sealed, grippy, or soft-touch interfaces.
- TPU/PC + LSR bonds
- IP-rated sealing
- Ergonomic grips
- Wearable & device skins
Medical-Grade LSR
ISO 10993 and USP Class VI capable silicones for single-use, diagnostic, and skin-contact devices.
- Lot traceability
- Clean-controlled molding
- Sterilization-ready
- Validation support
LSR vs TPU & Thermoplastic Elastomers
Why specifiers pick liquid silicone over TPE/TPU.
| Property | LSR | TPU / TPE |
|---|---|---|
| Temperature range | −50 to 200 °C | −40 to 120 °C |
| Biocompatibility | ISO 10993 / USP VI | Limited grades |
| Flash | Cold-runner: near zero | Parting-line flash |
| Steam/autoclave | Excellent | Degrades |
What Makes LSR Different from Thermoplastics
Liquid silicone rubber is a thermoset — it cures, not cools — which is why it keeps its properties where plastics soften.
Temperature resistance from −50 to 200 °C — the widest elastomer window we mold, surviving autoclave, steam and under-hood heat.
Biocompatible: ISO 10993 and USP Class VI capable grades for skin-contact and implant-adjacent devices, with lot traceability.
Excellent transparency, tear resistance and elasticity — the properties First Mold cites for medical and baby products are the same ones we run in our dust-controlled LSR cell.
Food-grade and BPA-free options (FDA 21 CFR / LFGB) for kitchenware, baby and beverage contact parts.
Chemical and weather resistance — seals and gaskets keep sealing in oils, solvents and UV without hardening.
Near-zero flash with cold-runner tooling — material waste and deflashing labor are both minimal.
LSR Grades and Overmold Substrates
We run the hardness range, medical/food grades and substrate combinations that cover most LSR programs.
LSR Tooling vs Thermoplastic Tooling
Medical, Wearable and Food-Contact Applications
Medical seals & diaphragms
Drug-delivery, diagnostic and surgical seals that must survive autoclave cycles — ISO 13485 lots with full traceability.
Baby products
Pacifiers, teats and feeding accessories in food-grade, BPA-free LSR — soft, transparent, tear-resistant.
Wearables & device skins
Skin-contact bands, buttons and IP-rated seals overmolded on PC electronics cores.
Automotive connectors & sensors
High-temperature silicone seals for connectors and sensor bodies, held to IATF 16949 process control.
Kitchen & food contact
Gaskets, spatulas and baking components in FDA 21 CFR / LFGB compliant LSR.
Optical components
Translucent light guides and covers with molded-in clarity and uniform transmission.