Liquid Silicone Rubber (LSR) Injection Molding - Hygienic Production 2025

Introduction to LSR Injection

Liquid silicone rubber (LSR) injection combines material flexibility with process precision. In medical, baby care, and food industries, it's valued for its biocompatibility, thermal resistance, and dimensional stability. Tederic Neo E injection molding machines equipped with LSR kits enable production of hygienic components without the risk of oil contamination. Servo drives and Industry 4.0 digital packages allow real-time process monitoring, with data integration into quality systems like ISO 13485 or BRC.

This article provides a complete roadmap for LSR implementation: from understanding the specifics of the two-component A+B material, to designing molds with cold plates, validation via IQ/OQ/PQ, and cleanroom ISO 8 maintenance. We supplement it with practical checklists, ROI examples, and process safety tips.

The global LSR market is growing at double-digit rates as consumers demand hygienic products suitable for food and body contact. We're also seeing regulatory pressure—manufacturers must demonstrate full traceability, control SVHC substances, and minimize carbon footprint. With digital monitoring and remote audits from Tederic, companies can prove every gram of material was processed under controlled conditions.

What is liquid silicone rubber injection?

LSR is a low-viscosity, two-component platinum-cure silicone that crosslinks at 120–200°C. Component A contains the polymer and fillers, while B has the catalyst. They are metered by gear or piston pumps at a 1:1 ratio, mixed in a static mixer, and injected into a hot mold. Within seconds, the material cures into a flexible, hygienic part. The process requires a cold nozzle and hot mold plate to prevent premature curing.

LSR injection differs from thermoplastics by eliminating the cooling phase—instead, mold temperature and cure time are critical. LSR-equipped injection molding machines feature special smooth-surface screws, airtight hoppers, and air-exclusion systems. The material's high flowability enables thin-walled parts (0.2–0,5 mm) with excellent repeatability.

LSR materials can be modified with pigments, conductive particles, or barrier additives, enabling functional parts like conductive buttons for electronics or medical tubing with radiopaque markers. However, additives must be mixed without disrupting curing. Static mixers are selected based on mixture viscosity and density, with parameters stored in HMI recipes.

History of LSR Process Development

Liquid silicone emerged in the 1970s, but metering pumps and cold-plate molds in the 1990s enabled high-volume production. Early applications included automotive seals and membrane switches. Over subsequent decades, LSR became standard in medical and baby products due to its odorlessness and sterilizability.

Recent years brought a digital revolution: in-mold pressure and temperature sensors, virtual commissioning, and automatic pump calibration. In 2023, Tederic introduced Smart LSR modules that integrate with MES systems and provide real-time reporting of material consumption, cycle counts, and energy per part. This gives companies a complete process overview and simplifies OEM customer audits.

Supply chain changes have also boosted LSR adoption. The pandemic and shorter production runs demanded flexibility—LSR injection allows quick product switches without material drying, and runnerless molds simplify cost control. In 2024, remote-diagnostic metering modules emerged, enabling Tederic service to predict pump seal wear and schedule replacements before downtime.

Types of LSR Injection

LSR technology includes several variants based on mold design and material feeding method:

• Standard LSR injection – two piston pumps feed components A and B, a static mixer prepares the blend, and a cold-plate mold with needle valves ensures uniform cavity fill.
• LSR with inserts (insert overmolding) – metal or plastic inserts are placed in the mold, and LSR forms the seal. Requires robots and precise positioning.
• LSR 2K / hybrid – one machine runs two units: one for LSR, one for thermoplastic, creating hard-soft combinations.
• Micro LSR – miniature metering systems and molds for parts under 0.1 g.

Variant selection depends on application, cycle time targets, surface quality, and automation integration. Tederic injection molding machines are designed for LSR modules on both new and existing Neo E/Neo H machines, shortening investment timelines.

Plug-and-produce configurations are increasingly common—pre-assembled metering skids mount to the machine frame and communicate with the PLC via Euromap 82.2. This reduces changeover times and eases line relocation between plants. For short-run production (e.g., personalized medtech), flexibility is key to profitability.

LSR for Medtech

Medtech uses LSR for catheters, infusion pump membranes, one-way valves, and tissue-contact implants. Requirements include sterility, biocompatibility, and compliance with ISO 10993 and USP Class VI. Production lines operate in ISO 7/8 cleanrooms, with all components designed for easy disinfection.

Tederic Neo E machines with LSR kits use all-electric drives and airtight enclosures to eliminate oileaks. Molds minimize parting lines to reduce particle risk. eDHR system integration assigns cycle parameters (pressure, temperature, cure time) to specific batches packaged in sterile bags.

Extracorporeal circulation and tissue-contact implant components are particularly demanding. They require medical-grade LSR with gamma-stability certification and platinum trace analysis. Tederic collaborates with material suppliers (e.g., Wacker, Momentive) to develop metering settings and cleaning procedures, documented in IQ/OQ/PQ validation reports.

LSR in Baby Care and FCM

In baby care, LSR is chosen for its softness, odorlessness, and high-temperature resistance. It produces pacifiers, bottle nipples, teether elements, and spill-proof cup valves. Materials must meet Food Contact Materials (FCM) requirements and EU/FDA migration standards, so processes must be controlled and free of volatile contaminants.

Manufacturers combine LSR with IML decoration or printing, requiring precise mold temperature control and repeatable surface prep. Automation includes pick-and-place robots, vision systems, and sometimes sterile cooling tunnels before packaging. Tederic Smart Monitoring analyzes cavity-to-cavity differences and responds quickly to weight variations.

FCM segments also favor vacuum packaging and inline inspection. AOI cameras check pacifier shape, while checkweighers verify part weight. Deviations trigger automatic rejection and quality reports. This minimizes recall risk, which is especially damaging to brand image in baby products.

LSR in Automotive

Automotive uses LSR for connector seals, HV wire covers, pressure sensor membranes, and LED lamp components. The material resists up to 200°C, UV radiation, and oils, making it ideal for engine compartments and e-mobility systems. Processes must meet IATF 16949 and PPAP standards.

Automotive LSR cells often integrate insert molding—robots load metal contacts, and LSR forms the housing. Cycle times of 30–50 s and leak testing at 100% are required. Euromap 77 and OPC UA feed machine data to SPC systems, automatically halting production on deviations.

E-mobility projects also use thermally conductive LSR injection for battery thermal management modules, where silicone acts as a soft thermal interface. This requires special molds and viscosity control, so operators use HMI recipes and interlocks that prevent cycles without blend confirmation.

Construction and Key Components

An LSR injection line comprises several integrated subsystems: injection molding machine, component metering unit, cold-plate mold, tempering system, downstream automation, and quality control. Every element must support hygienic operation and easy cleaning.

Tederic injection molding machines offer compact footprints for cleanroom enclosures. Installations follow GMP principles—cables run in disinfectable channels, and HMI panels have chemical-resistant glass fronts.

LSR lines also include support infrastructure: chillers for nozzle cooling, UPS power for pumps, and color dosing stations. Plants should include service zones for quick barrel changes without stopping production, using trolleys with quick-connects and level sensors.

Injection Unit

The LSR injection unit features short, smooth-surface screws to prevent swirling and dead zones. Servo-driven for high-volume repeatability—a typical 0,1 mm screw stroke yields 0,01 cm³ of mix. The nozzle is water-cooled, while the barrel is held at 20–25°C. This prevents premature curing in the plasticizing system.

Tederic units include nozzle pressure and temperature sensors for real-time mix viscosity control and holding pressure adjustments. An optional thermoplastic unit enables 2K parts (LSR + PC/PA), boosting part functionality.

Mold venting is also critical. Precision vent valves prevent air traps, and vacuum assist is used in micro projects. The machine controller logs nozzle and cavity pressure curves to verify venting effectiveness.

Metering System and Mold

The heart of an LSR line is the two-chamber metering system. It includes piston or gear pumps drawing from 20–200 l drums. Metering uses pressure sensors and flowmeters. Post-static mixer, the blend reaches the needle-valve nozzle. Air and moisture contact is prohibited, so all connections are hermetic.

LSR molds have cold plates with cooling channels, while cavities are heated to 150–200°C. This ensures curing only in the cavity. Runnerless molds with needle valves eliminate sprues. Cavities include Pt100 temperature sensors and piezoelectric pressure sensors for per-part cure profile analysis.

Mold designers also plan for automation: robot grip points, vision camera mounts, and plasma surface activation for printing. Tederic solutions integrate signal cables and heaters in one connector, speeding mold changes and reducing connection errors.

Key Technical Parameters

Managing LSR parameters requires precise measurements and automatic recipe adjustments. The key variables include:

• Mold temperature: 120–200°C depending on wall thickness and colorants.
• Cylinder/nozzle temperature: 15–25°C to keep the mixture fluid.
• Curing time: 8–60 s – shortens at higher temperatures and with catalysts.
• Injection pressure: 500–1500 bar with velocity profile control.
• Component dosing accuracy: ±0,5% by volume.

Tederic systems enable process visualization via HMI and cloud-based data archiving. Alerts are triggered by SPC trends – if curing time starts to increase, the system recommends filter replacement or temperature sensor calibration.

Environmental metrics are also tracked: energy per kg of production, cooling water usage, and silicone scrap volume. These KPIs are required by many OEM customers for ESG reporting and often determine new contract awards. Precise measurements enable companies to deliver climate-neutral projects backed by documentation.

LSR Injection Molding Applications

Applications include:

• Medtech: cannula plugs, pump membranes, respiratory components, ear implant parts.
• Baby care: pacifiers, mouthpieces, cup valves, teething rings, breast pump components.
• Food: baking molds, dispenser seals, sports bottle valves.
• Automotive: HV connector seals, wire covers, sensor membranes.
• Consumer electronics: soft-touch buttons, speaker membranes, smartwatch covers.

LSR is also used in the energy sector (high-voltage insulators), aerospace (vibration-dampening components), and household appliances (oven door seals). In every case, its dielectric properties, chemical resistance, and dimensional stability outperform traditional elastomers.

Luxury goods manufacturers use LSR for touch elements in audio electronics and fashion tech products. Its transparency and colorability make silicone ideal for lifestyle products, blending decorative appeal with protection of electronics from moisture.

How to Select the Right LSR Line?

Investment decisions should start with material analysis and regulatory requirements. Define the cleanroom class, planned volumes, and target cycle time. Next steps include:

• Selecting the injection molding machine model (Neo E, Neo H) and clamping force – typically 50–200 t for LSR applications.
• Choosing the metering unit (piston/gear pumps) and color preparation method (pigments, masterbatches).
• Mold design – number of cavities, valve gates, Euromap interfaces.
• Automation – robots, vision systems, cooling tunnels, sterile packaging.
• Integration with quality systems – eDHR, SPC, MES, ERP.

Tederic conducts process workshops simulating ROI scenarios (e.g., reducing cycle time by 6 s lowers unit cost by 8%). Working with material and tool suppliers, FAT/SAT tests are planned to minimize ramp-up time.

Don't overlook safety training and chemical safety protocols. LSR components must be stored at controlled temperatures, and staff need protocols for handling platinum catalysts and pigments. SDS documentation integrates with risk management systems, while leak sensors monitor pump and mixer areas.

Maintenance and Upkeep

LSR processing demands meticulous maintenance, as even minor contamination in the mixing system can cause material crystallization. Key actions include:

• Daily flushing of the mixer and nozzle with cleaning compound or special technical silicone.
• Weekly inspection of metering pumps – clearances, seals, filters.
• Monthly calibration of temperature sensors and flow meters.
• Monitoring humidity in LSR drum storage and using degassing systems.

The Smart Maintenance system logs pump runtime, nozzle cooling oil temperature, and servo drive vibrations. It generates maintenance schedules and spare parts lists. Mobile app integration lets technicians document tasks with photos, streamlining audits.

Implement downtime response procedures, such as emergency drum swaps or mold cleaning after accidental mix curing. Checklists and e-learning training ensure operators can safely stop processes and minimize losses. This is critical for 24/7 lines where every hour of downtime incurs major costs.

Summary

LSR injection molding balances hygiene requirements with high-volume production. With Tederic Neo E injection molding machines and Smart LSR modules, companies can quickly scale from prototyping to serial production with full process control. Optimal mold, automation, and quality system selection delivers lower TCO and faster ROI.

LSR implementation is not a one-off project but a transformation program spanning people, technology, and data. Continuous parameter monitoring, metering system maintenance, and team skill development ensure standards compliance and OEM expectations. This approach positions liquid silicone as a strategic material for medical, baby care, food, and automotive producers – delivering user safety and production predictability.