What temperature is used for LSR injection molding?

LSR molds typically run at 120-200 °C, with common production settings around 150-180 °C. Lower temperatures give longer cure times; higher temperatures cure faster but can scorch the silicone.

How is LSR shot weight controlled?

LSR is metered as a two-part system, and shot weight is controlled to about ±0.1% by the dosing unit to keep the mix ratio and part weight consistent across every shot.

Why does LSR need a cold runner and a hot mold?

The runner is kept cool so the mixed silicone stays fluid until it enters the cavity, while the mold is hot to trigger curing. This is the opposite of thermoplastics and prevents the material curing in the runner.

What affects LSR cure time?

Cure time depends mainly on mold temperature, wall thickness and the silicone grade. Thinner walls and higher temperatures cure faster; thick sections need more time for the center to reach curing temperature.

LSR Molding Key Process Parameters

Liquid silicone rubber (LSR) injection molding depends on a small set of tightly controlled process parameters. Get these right and you get consistent flash-free parts, repeatable shot weight and predictable cure — get them wrong and you get scorch, short shots and dimensional drift.

The Seven Parameters

What We Control on Every LSR Shot

Mold Temperature

LSR molds typically run at 120–200 °C, with most production settings around 150–180 °C. Temperature drives cure speed: too low and the part under-cures and sticks; too high and the surface scorches.

Injection Pressure & Speed

LSR is low-viscosity, so it fills at lower pressure than thermoplastics — but pressure must stay high enough to pack thin walls and ribs without trapping air. Injection speed is profiled to avoid jetting and air entrapment.

Shot Weight & Mix Ratio

LSR is a two-part A/B system metered at a precise ratio (commonly 1:1). Our dosing unit controls shot weight to about ±0.1% so part weight and the mix ratio stay consistent from shot to shot.

Cure Time

Cure time depends on mold temperature, wall thickness and grade. Thin walls cure in seconds; thick sections need more time for the core to reach curing temperature. We profile the cure per part rather than assuming a single cycle.

Clamping Force

Clamping force must exceed the injection pressure acting on the projected area, or the mold opens and flashes. We size clamping force from part area and pressure — a common source of flash in under-spec'd tooling.

Cold Runner Control

Unlike thermoplastics, LSR uses a cold runner to keep the mixed silicone fluid until it enters the cavity, while the mold stays hot to cure it. Keeping the runner cool prevents material from curing in the feed system.

Demolding & Venting

Vacuum-assisted venting removes trapped air that would otherwise leave bubbles or short shots, and demolding is timed so the part releases cleanly without tearing thin sections or sticking in deep cavities.

Why Parameters Matter

How Process Control Shows Up in the Part

Flash-Free Edges

Correct clamping and venting give clean parting lines without post-trimming.

Repeatable Dimensions

Stable temperature and shot weight keep dimensions within tolerance, shot after shot.

Faster, Consistent Cycles

A tuned cure time shortens the cycle without under- or over-curing the part.

Go Deeper Into LSR

LSR Components

See the LSR parts we mold — seals, gaskets, medical components and more.

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Manufacturing Engineering

Six engineering pillars including LSR rheology and shot-weight dosing.

Explore the pillars

Prototyping Methods

Compare aluminum-tool LSR and steel-tool LSR for prototype and production.

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Designing an LSR Part?

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