Liquid Silicone Rubber (LSR) Injection Molding Services
From mold design to mass production — precision LSR solutions for medical, automotive, and industrial applications.
An NDA can be signed if needed before the quotation.
What is Liquid Silicone Rubber Injection Molding?
Liquid Silicone Rubber Injection Molding (LSR) is a rubber processing technology that uses two-component liquid silicone rubber as raw material, and completes injection, vulcanization, and molding under high temperature conditions through precision molds. It combines the high precision of injection molding with the superior properties of silicone rubber, making it one of the core manufacturing technologies in high-end fields such as medical, automotive, and electronics.
LSR Core Material Properties
Operating Temperature range
-60°C ~ +200°C
Hardness Range (Shore A)
5A — 80A optional
Tear Resistance
Excellent, anti-fatigue cycle
Biocompatibility
ISO 10993 / FDA approved
Chemical Inert
Acid and alkali resistant, solvent resistant
Flame Retardant Rating
Up to UL94 V-0
Transparency
Optical-grade transparency can be achieved
Weather resistance
Anti-UV, ozone, aging
Liquid Silicone Rubber Injection Molding Process Flow
LSR injection molding is highly automated, with each step from raw material supply to finished product demolding controlled by precision equipment and process parameters.
Precise metering and mixing of two components
Components A and B are delivered in a precise 1:1 ratio via metering pumps and uniformly mixed in a static mixer. Simultaneously, a cooling system maintains a low temperature (approximately 5–15°C) in the delivery pipeline to prevent premature reaction of the materials.
Injection Molding
The mixed LSR is injected into a high-precision mold cavity under controlled pressure (typically 500–2000 bar) and speed by the injection unit. The low viscosity of LSR (approximately 50,000–300,000 mPa·s) allows it to fill extremely fine structural details.
High-Temperature Vulcanization and Curing
The mold temperature is maintained at 150–200°C, and the platinum-catalyzed addition reaction is completed within seconds to tens of seconds (the specific time depends on the wall thickness and product structure). No byproducts are generated, and the vulcanization process is clean and efficient.
Mold Opening and Part Removal (Automated Demolding)
After vulcanization, the mold is opened, and the LSR finished product is removed by an automated robotic arm or vacuum adsorption system. Due to the excellent elasticity of LSR, even complex structures (such as internal undercuts) can be easily demolded without the need for a release agent.
Post-treatment (on demand)
Some applications require a second vulcanization (post-cure, approximately 200°C / 4h) to remove residual volatiles and meet medical or food contact grade requirements. Some products require deflashing, surface treatment, or assembly.
| Criteria | LSR Injection MoldingLiquid Silicone Rubber | Compression MoldingSolid Silicone | TPE / TPU Injection MoldingThermoplastic Elastomer |
|---|---|---|---|
| Raw Material | Two-part liquid compound (A+B), mixed at 1:1 ratio before injection | Pre-vulcanized solid silicone blocks, cut to weight before molding | Thermoplastic pellets, melted and injected like standard plastic |
| Dimensional Accuracy | ±0.01 mm Precision-grade; suitable for tight-tolerance medical and automotive parts | Moderate Flash and shrinkage variation limit achievable precision | High Comparable to standard plastic injection molding |
| Production Efficiency | Fully automated Short cycle times; minimal manual intervention; scalable output | Labor-intensive Manual loading and flash trimming required; long cycle times | Fully automated Fast cycle times; compatible with high-speed production lines |
| Material Waste | Near-zero waste Cold runner systems eliminate sprues; no regrind needed | High flash waste Excess material overflows the parting line; significant post-trim scrap | Moderate Runners can be reground, though regrind affects material consistency |
| Temperature Range | −60°C to +200°C Stable across extreme thermal cycles without hardening or cracking | −60°C to +200°C Same thermal resistance as LSR, inherent to silicone chemistry | ≤ 120°C typical Performance degrades at elevated temperatures; not suitable for engine bay or autoclave environments |
| Biocompatibility | Excellent Meets FDA 21 CFR, ISO 10993, LFGB; no plasticizers or BPA; suitable for medical and food contact | Good Biocompatible grades available, though process cleanliness is harder to control | Grade-dependent Varies significantly by formulation; food-grade and medical-grade options exist but are limited |
| Complex Geometry | Excellent Low viscosity fills thin walls, fine details, and undercuts reliably | Limited Solid material resists flow into thin or intricate features; not suitable for thin-wall parts | Good Handles most geometries well; similar to standard injection molding capability |
| 2K / Overmolding | Fully supported LSR bonds directly to PC, PA, POM substrates in a single-shot 2K process; no adhesive required | Not supported Process constraints prevent integration with hard plastic substrates | Partial support Overmolding possible, but bond strength and durability are limited compared to LSR |
| Tooling Cost | Higher upfront Precision cold-runner molds require tighter machining tolerances and temperature control systems | Lower Simpler open-cavity molds; lower machining complexity and cost | Moderate Standard injection mold; less specialized than LSR tooling |
| High-Volume Economics | Highly scalable Unit cost drops significantly at scale; automation eliminates labor as a cost driver | Constrained Labor dependency caps throughput; cost per part remains high at volume | Excellent Low cycle time and full automation deliver strong economics at high volumes |
In what situations should Liquid Silicone Rubber Injection Molding be selected?
Suitable situations for LSR:
- The product needs to be used for extended periods in extreme temperature environments.
- It comes into contact with human bodies, food, or sterile environments.
- It requires high-precision, high-consistency, high-volume production.
- The product has a complex structure, including thin walls, details, or undercuts.
- It requires a combination of rigid and flexible molding (2K molding).
- It is sensitive to flash and post-processing costs.
Situations requiring consideration:
- Very small sample size (<100pcs), high mold investment
- Extremely cost-sensitive with low performance requirements (TPE can be considered)
- General sealing required for room temperature use (TPE can cover this)
- Extra-large, thick-walled products (compression molding may be more suitable)
What Can We Do For Your LSR Project?
Exclusive advantages
Own mold factory · Entirely self-developed
We have our own independent LSR precision mold workshop, eliminating the need for outsourcing from design to manufacturing. Mold quality is fully self-controlled, delivery times are predictable, and data and processes are kept confidential.
- Integrated mold design, CNC machining, EDM, and polishing.
- Avoids the risk of information leakage from outsourced mold factories.
- Faster response to engineering changes and lower mold repair costs.
- Guaranteed mold lifespan and high long-term mass production stability.
Reduce early risks
DFM Manufacturability Analysis - Design Phase Intervention
Before mold making, our engineering team will conduct an in-depth Design Factor Analysis (DFM) review of your design to identify potential issues in LSR molding, such as wall thickness, demolding, flash, and venting, thus avoiding rework after mold making.
- We provide a free DFM report with feedback within 24 hours.
- We offer specific suggestions such as wall thickness optimization and parting line adjustment.
- We reduce the number of trial moldings, saving 30-50% on upfront mold modification costs.
Quick Verification
Rapid 3D Prototyping & Pre-Production Structural Verification
Before formal mold making, we offer rapid prototyping via 3D printing or silicone soft molds, helping you complete product structure, function, and assembly verification at the lowest cost.
- Physical samples delivered within 7 days.
- Supports both hard mold prototyping and rapid soft mold verification.
- Effectively reduces mold making risks caused by design uncertainties.
Process expansion
LSR + Rigid Adhesive Two-Component Molding
Supports secondary injection molding and overmolding of LSR with rigid substrates such as PC, PA, and POM, achieving a rigid-flexible integrated structure without additional bonding processes, thus improving product structural integrity.
- Suitable for sealing buttons, handheld device grips, medical connectors, etc.
- Interfacial bond strength has been process-verified, demonstrating excellent tear resistance.
- Reduces the number of parts, lowering assembly costs.
Compliance support
Medical-grade / Food-grade Material System
We partner with certified raw material suppliers to provide LSR raw materials that meet FDA, ISO 10993, LFGB, and other standards, and can assist in issuing material compliance documents to support your certification process.
- Materials are traceable and subject to strict batch management.
- We support material selection from well-known brands such as Wacker, Shin-Etsu, and Momentive.
- We can provide Material Safety Data Sheets (SDS) and compliance certificates.
Flexible capacity
From Small-Batch Prototyping to Mass Production of Millions of Units – Covering the Entire Process
We don’t set high MOQ thresholds. Whether it’s a proof-of-concept batch of 500 units or a stable production run of millions of units per month, we can flexibly accept orders and support your product from scratch to scale.
- Friendly for startups and new product development.
- Seamless switching from prototyping to mass production using the same mold.
- Capacity can be expanded as needed, with stable and controllable delivery times.
Manufacturing Specifications Reference
Dimensional tolerances
±0.01 mm
Precision parts can reach ±0.005 mm
Minimum wall thickness
0.3 mm
Depending on structural complexity
Product weight range
0.1g — 500g
Covering micro to medium-sized products
Number of mold cavities
1 — 128 cavities
Customized according to production requirements
Hardness range
5A — 80A
Shore A, custom formulations available
Mold life
≥ 500,000 cycles
High-quality steel + meticulous maintenance
Unsure if your project is suitable for the LSR process?
Send your design files, and we’ll provide a free DFM analysis report and process recommendations within 24 hours.
Industry Applications & Solutions
The true value of LSR lies in solving manufacturing challenges that other materials simply cannot meet. Below is our hands-on application experience across five key industries.
- Parts must meet FDA / ISO 10993 biocompatibility standards — material qualification is demanding and time-consuming
- Production cleanliness is critical; even trace particulate or organic contamination is unacceptable
- Dimensional consistency is directly tied to diagnostic accuracy and patient safety — batch-to-batch variation cannot be tolerated
- Many components must withstand repeated sterilization cycles, including EO sterilization and steam autoclaving at 134°C
- Chemically inert — does not react with bodily fluids or pharmaceutical compounds; safe for long-term human contact
- Platinum-catalyzed addition curing produces zero by-products, supporting clean manufacturing environments
- Withstands repeated autoclave sterilization without degrading, hardening, or losing dimensional integrity
- Optically transparent grades available for fluid channels, inspection windows, and diagnostic components
Key Application Products
- Under-hood temperatures can exceed 150–200°C — standard rubber and TPE compounds fail under sustained thermal stress
- Seals must maintain elasticity across a full operating range of −40°C to +200°C without hardening or cracking
- EV battery systems increasingly demand IP67/IP68-rated sealing against water, dust, and chemical ingress
- IATF 16949 quality requirements mandate ultra-low PPM defect rates and verified process capability (Cpk)
- Industry-leading thermal stability makes LSR the first choice for high-temperature sealing zones
- Outstanding compression set resistance ensures seals retain clamping force over years of thermal cycling
- Resistant to engine oils, coolants, brake fluids, and other automotive service chemicals
- Precision injection molding minimizes flash and dimensional scatter, supporting strict assembly tolerances
Key Application Products
- Product cycles are short — the window from design to mass production is often just 3–6 months
- Cosmetic parts demand flawless surface quality; flash, sink marks, and flow lines are not acceptable
- Wearable devices in direct skin contact must pass skin irritation and sensitization testing
- Increasing complexity: thin walls, miniaturization, multi-color construction, and integrated waterproofing
- Low viscosity faithfully replicates fine mold surface detail, producing consistent cosmetic quality at scale
- Achieves matte, translucent, and optical-grade transparent finishes depending on mold surface treatment
- 2K co-injection with PC/ABS substrates integrates structure and sealing in a single manufacturing step
- Addition curing produces no volatile by-products — clean molding environment supports precision surface finish
Key Application Products
- Rapidly evolving sector — product designs change frequently, demanding manufacturing partners that can respond quickly
- Robotic joint components undergo millions of flex cycles; fatigue failure is a critical failure mode
- Energy storage seals must perform reliably across −30°C to 85°C and resist electrolytes and coolants long-term
- Low-volume, high-mix production profiles make cost control in custom parts especially challenging
- Exceptional fatigue life — LSR maintains its elastic properties through millions of flex, compression, and tension cycles
- Low compression set ensures seals remain effective over long operating periods, reducing maintenance frequency
- The same mold supports low-volume prototyping and high-volume production — no retooling cost between phases
- Resistant to lithium battery electrolytes, thermal management fluids, and other energy system chemicals
Key Application Products
Ready to Start Your LSR Project?
Get a free DFM analysis and custom quote in 48 hours.
FAQ
There is usually no absolutely fixed MOQ, but due to the higher costs of molds and equipment, LSR is more suitable for medium to large-volume production. For small-batch projects, upfront costs can be reduced by optimizing the mold design.
Generally, the tolerance of LSR injection molded parts can be controlled within ±0.02mm to ±0.05mm, depending on the product structure, size and mold precision.
Yes. LSRs are well-suited for use with metal or plastic inserts to achieve functions such as sealing, waterproofing, or structural reinforcement, but positioning and bonding issues need to be fully considered during the mold design phase.
LSR requires extremely high mold precision. If the mold design and processing control are appropriate, a near-burr-free production effect can be achieved.
Mold development typically takes 2-4 weeks, while mass production cycle depends on order quantity and generally ranges from 1-3 weeks.
Yes. LSR materials naturally possess excellent transparency, making them suitable for applications requiring high light transmittance, such as optics, medical devices, and electronic products.
It can generally be used for a long time in the range of -50℃ to 200℃, and some special formulas can withstand higher or lower temperature environments.
Yes. Colors can be customized according to customer needs, including transparent, semi-transparent, and various custom colors, but batch consistency control must be considered.
Yes. LSR has good flowability and can fill complex, thin-walled, or microstructured mold cavities, but the design needs to conform to its flow characteristics.
Standardized process parameters, automated production equipment, and strict quality control procedures can effectively guarantee the stability and consistency between batches.