Liquid Silicone Rubber Overmolding Processing Service

# Liquid Silicone Rubber Overmolding Processing Service

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Product Overview

Liquid Silicone Rubber (LSR) overmolding is a specialized multi-shot injection molding process that bonds liquid silicone rubber to rigid substrates (including plastics, metals, glass, and engineering polymers) to create integrated, high-performance composite components. Our Liquid Silicone Rubber Overmolding Processing Service delivers custom turnkey solutions from prototyping to mass production, leveraging 15+ years of LSR processing expertise and Class 100,000 cleanroom production facilities to meet the strict requirements of medical, automotive, consumer electronics, and industrial applications.

Unlike traditional post-assembly bonding methods, LSR overmolding creates a permanent molecular bond between silicone and the substrate, eliminating adhesive failure risk, reducing assembly labor costs, and enabling complex geometric designs that cannot be achieved with separate manufacturing. Our service supports low-volume prototyping (1–100 units) for product development and high-volume mass production (up to 10 million units annually) for commercialization, with full design-for-manufacturing (DFM) analysis included in every project to optimize performance and reduce production costs. We work directly with product designers, OEMs, and contract manufacturers to adapt to unique application requirements, from ultra-soft gaskets to high-toughness structural overmolds.

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Technical Specifications

Material Properties

All LSR materials used in our overmolding process are sourced from global leading suppliers (Dow Corning, Shin-Etsu, Wacker Chemie) to ensure consistent performance. Supported material grades include:

Physical Performance

Our overmolded components meet the following performance benchmarks:

• Bond strength: ≥1.2 MPa (tensile shear strength between LSR and PC substrate; no delamination under accelerated aging tests)
• Tensile strength: 3.5 MPa – 10.5 MPa (depending on LSR hardness grade)
• Elongation at break: 200% – 800%
• Compression set (22h @ 175°C): ≤10% (standard medical grade)
• Volume resistivity: 1×10¹² – 1×10¹⁶ Ω·cm (insulating grades); 1 – 100 Ω·cm (conductive grades)
• Thermal conductivity: 0.2 W/(m·K) (standard) – 2.0 W/(m·K) (high thermal conductivity grades)

Process Parameters

We control all process parameters to ensure consistent quality across production runs:

• Injection pressure: 50 bar – 150 bar (adjusted for part thickness and geometric complexity)
• Mold temperature: 150°C – 190°C
• Curing time: 30 seconds – 180 seconds (depending on LSR wall thickness)
• Maximum part size: 400 mm × 300 mm × 100 mm
• Minimum LSR wall thickness: 0.2 mm
• Tolerance control: ±0.02 mm for features smaller than 10 mm; ±0.05 mm for features larger than 10 mm

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Product Advantages

1. Permanent, Reliable Bonding Without Adhesives

Our optimized injection molding process and surface pretreatment technology (plasma treatment, primer coating for high-bonding-demand substrates) create a covalent molecular bond between LSR and the substrate, eliminating the risk of delamination, adhesive residue, or bond degradation under extreme temperature or chemical exposure. This improves product service life by 30–50% compared to post-assembly adhesive bonding methods.

2. Cost-Effective Integrated Manufacturing

LSR overmolding combines multiple components into a single integrated part, reducing secondary assembly steps, labor costs, and inventory management complexity. For high-volume production, we can reduce overall product cost by 15–25% compared to assembling separate silicone and rigid components. We also support automated insert loading for continuous mass production, ensuring consistent output and low per-unit cost.

3. Strict Compliance for Regulated Industries

All our food-grade and medical-grade LSR materials are fully compliant with FDA 21 CFR 177.2600, USP Class VI, ISO 10993 biocompatibility, and EU REACH regulations. Our production facilities follow GMP (Good Manufacturing Practice) standards, with full traceability for every batch of raw material and production run, supporting regulatory approval for medical devices and food contact products.

4. Design Flexibility for Complex Geometries

Our precision mold manufacturing technology and low-viscosity LSR injection process support thin-walled overmolding, micro-feature replication, and complex 3D contours that cannot be achieved with compression molding or post-assembly. We can produce overmolded parts with seamless transitions between LSR and rigid substrates, improving aesthetic quality and reducing irritation for skin-contact products.

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Applications

Our LSR overmolding processing service serves a wide range of industrial and commercial applications, with proven use cases including:

• Medical Devices: Surgical instrument handle grips, syringe plunger gaskets, inhaler seals, wearable glucose sensor overmolding, urinary catheter cuffs, and dental device components. The biocompatible, sterilizable nature of LSR makes it ideal for repeated clinical use and implantable devices.
• Automobile Industry: LED headlight gaskets, connector seals, steering wheel overmolded grips, sensor housing gaskets, and electric vehicle battery module thermal pads. LSR provides long-term resistance to automotive fluids, UV radiation, and temperature cycling, meeting IATF 16949 quality requirements.
• Consumer Electronics: Smartwatch watchband overmolding, waterproof sealing gaskets for smartphones and wearables, power tool handle grips, and USB connector insulation overmolding. We can produce soft-touch, anti-slip grips with consistent texture and excellent scratch resistance.
• **Household and Food Industry: Food container sealing gaskets, baby bottle nipple overmolding, kitchen tool handle grips, and coffee machine sealing components. Our food-grade LSR is free of BPA, phthalates, and other harmful additives, resistant to repeated washing and high-temperature sterilization.
• **Industrial Equipment: Hydraulic seal overmolding, vibration-damping mounts for precision machinery, and protective overmolding for electrical connectors. LSR provides excellent chemical resistance and aging stability for long-term industrial use.

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Selection Guide

Hardness Selection

Choose LSR hardness based on your application requirements:

• 10–20 Shore A: Ultra-soft, for skin-contact wearable devices, sealing gaskets requiring high compression flexibility
• 30–50 Shore A: General purpose, for handle grips, standard sealing gaskets, watchbands
• 60–80 Shore A: High-toughness, for structural overmolding, high-pressure seals, heavy-duty industrial components

Size Specifications

We support custom overmolding for all part sizes within our process range:

• Small components (≤50 mm): Ideal for micro medical devices, electronic connectors, minimum order quantity (MOQ) of 50 units for prototyping
• Medium components (50–200 mm): Most common for handles, gaskets, watchbands, MOQ of 20 units for prototyping
• Large components (200–400 mm): For automotive housings, industrial seals, MOQ of 10 units for prototyping

Material Grade

Select the appropriate LSR grade based on your regulatory and performance requirements:

• Medical Grade: Compliant with ISO 10993 and USP Class VI, for medical devices and implantable components
• Food Contact Grade: Compliant with FDA 21 CFR 177.2600, for kitchenware and food processing equipment
• Industrial Grade: Cost-effective general purpose, for non-critical industrial and consumer applications
• Functional Grade: Flame-retardant (UL 94 V-0), electrically conductive, or thermally conductive for special performance requirements

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Quality Assurance

We maintain a full quality control system covering every stage of the overmolding process from raw material incoming inspection to final product shipment:

1. Raw material inspection: Every batch of LSR and substrate is tested for hardness, purity, and compliance with material specifications before production
2. In-process inspection: Dimensional inspection of first article parts, real-time monitoring of process parameters to ensure consistency
3. Final product testing: We provide custom testing services including bond strength testing, biocompatibility testing (third-party accredited), compression set testing, and leak testing per customer requirements
4. Certifications: Our facility is certified to ISO 9001:2015, IATF 16949, and ISO 13485 for medical device manufacturing, with full traceability for all materials and production records to support customer regulatory audits.

All products are inspected in our cleanroom before packaging, and we offer 100% inspection service for critical medical and automotive applications. We provide a 12-month performance warranty for all overmolded components, with free rework or replacement for any quality-related issues.