Mold Type

Silicone Molding Parts & LSR Injection Molding

Silicone molding has become one of the most adaptable plastic fabrication techniques around — from toy making to custom automotive interior prototypes. It yields parts with high dimensional accuracy, holding tolerances as tight as ±0.005".

What Is Silicone Molding?

Flexible parts, precisely shaped.

Silicone molding is the use of silicone to shape usable products, cast into materials like polyester, polyurethane wax, plaster, concrete, epoxy resins and polyurethane foam. It makes those materials stronger and more chemical resistant, giving them a longer lifespan.

High Consistency Rubber (HCR) silicone has a high viscosity, similar to peanut butter, and can be catalyzed with platinum or peroxide. It's typically compounded on a two-roll mill, then molded using compression or transfer molding — the two main HCR methods.

Dimensional tolerance

± 0

2–4%

Typical part shrinkage

HCR / LSR

Both molding types supported

Getting Started

Design Steps For Silicone Molding Parts

A few core concepts to understand before designing a silicone mold.

01

Adjust the Gate Location

Gates should sit on hidden, insignificant faces. Direct gating channels silicone straight into the cavity through the runner system; sub-gating directs it beneath the cavity to a specific lower area.

02

Parting Lines

Before building the mold, decide where the two halves connect. Flashing typically shows at this line, so it should sit on second- or third-level surfaces that are less noticeable.

03

Part Shrinkage

Expect 2–4% shrinkage on molded silicone parts, with some parts shrinking up to an extra 1% after molding. Higher-quality fabrication may need extra steps to account for this.

HCR Molding Methods

Ways We Mold Silicone Parts

HCR silicone can be injection molded a few different ways, depending on the part and production volume.

01

Compression Molding

Material is compressed between two heated plates, squeezing the extruded material out along the parting line. It's older technology, but still one of the most affordable ways to fabricate custom silicone parts in small volumes.

02

Transfer Molding

Similar to compression molding, but high pressure (roughly 1,500–2,000 psi) forces material into the cavity through a runner, sprue and gate system — well suited to low-to-medium annual production volumes.

03

Overmolding

Silicone is laminated onto a substrate, giving the finished product the characteristics of both materials. This uses LSR molding equipment and specific tooling — insert misplacement is the main risk to watch for.

04

Two-Shot Silicone-Thermoplastic

The first part is injection molded in one half of the mold, then silicone is overmolded onto it in the second half. Requires high-temperature-resistant tools, self-bonding LSR material and skilled operators.

Know The Difference

Rubber Molding vs. Silicone Molding

Both processes create a wide range of shapes, but the materials and results differ in some key ways.

Rubber Molding

Silicone Molding

Carried out at room temperature
Usually doesn't need a release agent
Easier to produce shapes close to the original mold
Produces parts with high chemical resistance
Shrinks more — storage needs more care

How LSR Injection Molding Works

From tooling to finished part.

Liquid silicone injection molding starts with CNC machining the mold tool, built to endure high process temperatures, then sanded to the desired surface finish. The tool goes into an LSR molding machine, where a high-precision press controls shot size for consistent quality.

LSR is a thermosetting polymer — once molded, it can't be remelted like thermoplastics. After molding, parts are ejected and ready for use as prototypes or production parts, serving medical, lighting and automotive applications among others.

Common Uses

Where LSR Parts Show Up

Gaskets and flanges
Cushioning pads for portable communication equipment
Ruggedized electronic product components
Parts requiring a wide range of hardness or elasticity
High-durability parts for demanding, high-stress applications

Design Guide

LSR Injection Molding Design Guide

A few design considerations to increase the effectiveness of your molded parts.

Undercuts & Draft Angles

Undercuts add cost and complexity to ejection — use pass-thru coring to minimize them, and design draft angles between 0.5° and 5° for easy demolding.

Wall Thickness

Even wall thickness avoids sinks and voids. Thinner walls also cut cycle time and total production cost.

Ribs & Gussets

Rib thickness should run 40–60% of the outer wall thickness, with proper draft, to support the design without excess pressure.

Hole Bosses

Hole bosses should be drilled to 30% of wall thickness, with edge grooves at 30% too — secured to side walls or ribs for strength.

Why Sincere Tech

High-Standard Quality Rubber & Silicone Parts

Sincere Tech is a professional custom silicone molded parts supplier, trusted for delivering rubber molding parts and silicone molding parts at competitive prices — built by skilled professionals using advanced technology and quality material for durability and high tensile strength.

Advanced tools and quality materials for strong, durable part structures
Continuous improvement focus to reduce labor costs for customers
Products available in both solid and sponge characteristics, customizable to spec
Portfolio meets international demand and strict ISO and FDA standards, at competitive prices
A team of engineers and advanced silicone production equipment ready for your requirements

Start Your Project

Have a part to manufacture? Let's make it production-ready.

Send your drawings, 3D files or project requirements and our team can review the next step.