Liquid Silicone Rubber Injection Molding
Develop precision liquid silicone rubber parts with controlled material metering, mold design, injection processing and repeat production support. NEWTOP reviews your application, geometry, tolerance, material and volume before recommending an LSR molding route.
Precision Parts
Suitable for small features, sealing structures and parts requiring controlled repeat dimensions.
Complex Geometry
Low-viscosity LSR can fill detailed cavities, thin sections and selected difficult structures.
Repeat Production
Automated metering and molding can support stable cycles and higher-volume manufacturing.
Integrated Components
Selected projects can be reviewed for insert molding, overmolding or cleaner production routes.
What Is Liquid Silicone Rubber Injection Molding?
Liquid silicone rubber injection molding uses a two-component, platinum-cured silicone material. Components A and B are pumped from separate containers, accurately metered and mixed, with pigment or other approved additives introduced when required.
The mixed material is kept relatively cool before entering the mold, then injected into a heated cavity. Heat initiates rapid crosslinking and converts the liquid material into a solid, elastic silicone component.
- Two-component material is normally metered at the specified ratio
- Material temperature is controlled before it reaches the mold
- The mold cavity is heated to initiate curing
- Injection pressure, speed and cure time are adjusted by part
- Parts are demolded, inspected and finished as required
How the LSR Injection Molding Process Works
Stable production depends on more than injecting material into a mold. Metering, mixing, mold temperature, venting and cure conditions must work together.
Material Feeding
Components A and B are supplied from separate pails or drums through a controlled pumping and dosing system.
Metering and Mixing
The two components are accurately metered and mixed. Color or selected additives can be introduced according to the confirmed formulation.
Injection and Filling
The mixed LSR is injected through the runner and gate system into the closed, heated mold cavity.
Heat Curing
Mold heat initiates crosslinking. Cure time is adjusted according to the material, part thickness and mold conditions.
Demolding and Inspection
The cured part is removed, followed by visual inspection, dimensional checks, deflashing or other project-specific steps.
Why Use LSR Injection Molding?
LSR is valuable when the product requires precision, complex filling, repeatability or an efficient automated production route.
Detailed Cavity Filling
The flow characteristics of LSR can support fine features, thin sections and complex sealing structures when the mold and venting system are properly designed.
Fast Heat Cure
Suitable LSR grades can cure rapidly in a heated mold, helping reduce cycle time compared with some traditional silicone molding routes.
Automated Processing
Metering, mixing and injection can be highly automated, reducing unnecessary material handling and supporting consistent repeat production.
Application-Specific Grades
LSR is available in different hardness, transparency, sealing, food-contact, healthcare, electrical and self-bonding directions. Final selection must be grade-specific.
Critical Design Factors for LSR Parts
LSR can fill complex structures, but low viscosity also increases sensitivity to flash, venting, shutoff quality and mold precision. These details should be reviewed before tooling begins.
Wall Thickness
Avoid unnecessary thickness variation. Thick areas usually require longer curing, while very thin areas can create filling or tearing risks.
Parting Lines and Shutoffs
Low-viscosity material can enter very small gaps. Mold precision and shutoff design directly affect flash level and trimming requirements.
Gate Position
Gate location affects filling balance, weld areas, air movement, visible marks and the way the finished part is removed from the runner.
Venting
Venting must allow displaced air to escape without creating excessive flash. Poor venting can cause short shots, burns or trapped air.
Undercuts and Demolding
Silicone flexibility allows selected undercuts, but the geometry, hardness, tear strength and removal direction must be evaluated together.
Tolerance and Shrinkage
Critical dimensions should be identified in advance. Final tolerance depends on part geometry, material, cavity design and stable process conditions.
Texture and Finish
Mold polish and texture affect appearance, release behavior and cleaning. Functional sealing surfaces should be clearly separated from decorative surfaces.
Bonding and Overmolding
Substrate material, surface preparation, insert location and bonding route must be confirmed before an LSR overmolding project proceeds.
LSR Manufacturing Options by Project Requirement
The molding cell and tool design should be selected according to the part, insert requirements, cleanliness needs and volume.
Precision LSR Molding
For custom silicone seals, valves, membranes, connectors, covers and precision molded components.
- Cold-runner tooling review
- Single or multi-cavity production
- Custom hardness and color
- Repeat dimensional inspection
Insert and Overmolding
For selected components requiring silicone molded over metal, plastic or another compatible substrate.
- Insert and substrate review
- Mechanical retention assessment
- Primer or self-bonding route
- Insert positioning and protection
ISO 8 Cleanroom Route
For selected healthcare, medical and higher-requirement parts needing cleaner molding, handling or packaging.
- Project-specific cleanroom review
- Cleaner handling and inspection
- Batch and document support
- Packaging route confirmation
LSR Injection or HCR Compression Molding?
LSR is not automatically the best route for every silicone part. Product structure, tooling investment, tolerance and volume should determine the process.
| Project Factor | LSR Injection Molding | HCR Compression Molding |
|---|---|---|
| Typical Fit | Precision, complex or higher-volume parts | General molded parts, varied sizes and lower initial volume |
| Material Form | Pumpable two-component liquid silicone | Solid high-consistency silicone compound |
| Automation | High automation potential for feeding and molding | Often requires more material preparation and manual handling |
| Complex Features | Strong capability for fine features and detailed filling | Suitable for many structures but flow behavior is different |
| Tooling Investment | Usually higher because of precision tool and runner requirements | Often more economical for simpler parts and initial quantities |
| Production Volume | More attractive when repeat volume supports the tooling route | Flexible for prototypes, small batches and mass production |
Final process selection should be based on the drawing, critical dimensions, expected volume, material and functional requirements.
Control the Material, Mold and Process Together
Stable LSR production depends on controlling more than the final appearance. Material batches, process settings, tooling condition and inspection standards should be confirmed before mass production.
What We Need to Evaluate Your LSR Project
Complete information helps us assess whether LSR injection molding is suitable and identify material, tooling and process risks before quotation.
Need a Manufacturing Route for Your LSR Part?
Send your drawing, application, target material, tolerance, estimated volume and testing requirements. Our team will review whether LSR injection molding is suitable and identify the next tooling and sampling steps.
LSR Injection Molding Questions
What is the difference between LSR and HCR silicone?
LSR is a pumpable two-component liquid material normally processed through injection molding. HCR is a solid high-consistency compound commonly processed by compression, transfer or extrusion methods. The suitable route depends on part structure, volume, tolerance and tooling budget.
Is LSR injection molding suitable for small quantities?
It can be used for lower quantities, but the precision tooling and runner system usually create a higher initial investment. For early prototypes or simple low-volume parts, another process may be more economical.
Can LSR be molded over plastic or metal?
Selected projects can use LSR overmolding or insert molding. The substrate, temperature resistance, surface condition, bonding route and insert positioning must be reviewed before tooling begins.
Does every LSR material meet FDA or medical requirements?
No. Compliance and healthcare suitability depend on the specific material grade, colorant, processing conditions, finished part and required testing scope. Documentation should be confirmed for each project.
Can LSR parts be produced in an ISO 8 cleanroom?
Selected LSR projects can be reviewed for ISO 8 cleanroom molding, handling, inspection or packaging. The route depends on the part, cleanliness expectation, documentation and packaging requirements.
What files are required for an LSR quotation?
A STEP, STP, IGES or SolidWorks file is preferred, together with a 2D drawing showing critical dimensions and tolerances. Please also provide the application, material requirements, expected quantity and testing needs.