From Substrate to Finished Part: Liquid Silicone Rubber Manufacturing Explained

Liquid Silicone Rubber (LSR) manufacturing is a critical part of regulated industries such as medical, pharmaceutical, and defense. Converting a raw substrate into a precise, high-performing component requires more than the material itself — it involves precise molding techniques, rigorous quality control, and careful adherence to design standards. Examining how each stage — from material selection to final molding — works together illustrates why these components are dependable, reliable, and fully compliant for regulated uses.

 

LSR manufacturing for medical and regulated industries

This material is widely used in medical, pharmaceutical, and aerospace/security sectors, where precision, reliability, and regulatory compliance are essential. Its platinum-cured thermoset elastomer properties provide excellent biocompatibility, dimensional stability, and resistance to sterilization processes, making it ideal for devices that must perform safely under demanding conditions.

ProMed brings more than 35 years of experience in silicone molding, delivering consistent results and technical expertise across complex projects. ISO 13485 certification, FDA registration, and ITAR compliance ensure each component meets rigorous standards, supporting regulated work from prototype through full-scale production.

 

Critical industries that depend on LSR manufacturing

Many regulated industries rely on high-performing components to meet exacting standards. From medical devices to aerospace systems, these sectors demand parts that combine durability, precision, and biocompatibility — qualities that make LSR indispensable for critical uses.

 

Medical device manufacturing

In medical device work, this elastomer is key to creating precise, reliable components. Its biocompatibility, dimensional stability, and sterilization resistance make it suitable for both short-term and long-term implantable devices. Uses include drug-delivery systems, implantable devices, and micro-molded parts for minimally invasive procedures.

ProMed applies advanced molding techniques to ensure each component meets strict regulatory and functional standards. The resulting parts maintain integrity, consistent performance, and patient safety under demanding conditions. Combined with its versatility and material properties, this material plays a fundamental role in modern medical device manufacturing.

 

Pharmaceutical and combination device applications

LSR is equally critical in pharmaceutical and combination device work, where medical devices integrate with drug therapies. Components such as steroid plus and drug-eluting devices rely on precision and material stability.

Selecting the appropriate material choice ensures compatibility with active pharmaceutical ingredients and accurate drug release profiles. With specialized facilities and advanced molding capabilities, ProMed produces these complex components efficiently, maintaining both regulatory compliance and functional reliability.

 

Aerospace, defense, and specialized uses

Aside from the medical and pharmaceutical sectors, the aerospace and defense industries depend on silicone for high-performing, specialized components. Some common examples include wire harness seals, vibration dampers, environmental seals, and desiccants.

Advanced molding techniques allow for the fabrication of customized parts that meet stringent specifications, ITAR, and DoD standards. These capabilities illustrate how this process underpins the reliability and safety of critical aerospace and defense systems.

 

What makes LSR the material of choice for demanding applications?

This compound is often the preferred option for work that requires high precision, durability, and regulatory compliance. Its biocompatibility, resistance to extreme temperatures, and long-term stability make it especially valuable for medical, pharmaceutical, and aerospace components.

It withstands repeated sterilization cycles and harsh chemical exposure, ensuring components maintain their integrity in challenging environments. Its low viscosity allows the compound to flow into intricate geometries while consistently meeting tight tolerances, enabling the fabrication of complex, high-performing parts.

Additionally, it is an effective electrical insulator, resistant to bacterial growth, and maintains its properties over long-term use. Superior compression set characteristics ensure reliable sealing and mechanical stability across demanding applications where consistency is critical.

 

Exploring the LSR manufacturing process

Understanding this molding process is critical for producing reliable, high-performing components.

The workflow begins with a two-part system and precision metering, followed by injection molding in Class 7 cleanroom environments.

After molding, parts undergo demolding, secondary operations, and inspection, if required, to ensure consistently flawless end products.

 

Two-part material system and precision metering

A two-part system is fundamental to this process, consisting of Part A (base) and Part B (platinum catalyst). These components are stored separately to prevent premature curing. Automated mixing ensures a precise 1:1 ratio, with optional color pigments or radiopaque materials added for product differentiation.

ProMed’s precision metering guarantees consistent delivery for each production run. This accuracy is essential for reproducibility and reliability, meeting the high standards required in medical, pharmaceutical, and aerospace work.

 

Injection molding in clean environments

Injection molding is performed in class 7 cleanrooms to ensure precision, cleanliness, and consistent part results. The controlled environment supports optimal curing, dimensional accuracy, and compliance with regulatory standards.

• Injection is generally carried out at temperatures between 350 and 400°F to achieve proper platinum curing (lower cure temperature material options are available for special applications).
• Machines range in tonnage from 11 to 240 tons to accommodate varying shot sizes.
• Shot sizes can range from 0.5 ccm to 180 ccm, allowing for both small and large-volume production runs.
• Cold runner systems are used to reduce waste and improve efficiency.
• Alternative processes, including compression molding, are available for specialized needs.

This approach ensures that every component is manufactured reliably and meets strict industry and functional requirements.

 

Demolding, secondary operations, and quality verification

After molding, components are carefully demolded, either manually or automatically, taking advantage of silicone’s flexibility. Secondary operations may include deflashing, post-curing, printing or marking, assembly, and overmolding.

The final verification phase includes detailed visual inspections, dimensional checks, and functional testing to ensure each part meets exacting standards. ProMed’s integrated approach ensures engineering, fabrication, and verification teams collaborate at every stage, delivering reliable, compliant components across all projects.

 

Design guidelines for LSR components in regulated industries

Designing components for regulated industries requires careful attention to geometry, tolerances, and manufacturability to ensure high-grade, reliable parts. Following established guidelines helps maximize functionality while minimizing defects during fabrication.

• Wall thickness should generally range from 0.020″ to 0.250″ and remain as uniform as possible to avoid sink, though this elastomer can tolerate some degree of variation without compromising part integrity.
• Draft angles are not strictly required, which allows for reasonable undercuts and complex features when necessary.
• Geometric features, including sharp corners, are possible, though incorporating radii is recommended for implantable components to reduce stress while molding.
• Parting lines and gate placement can significantly affect flow and surface finish, and ProMed’s Design for Manufacturability (DFM) analysis ensures optimal positioning.

Following these principles helps ensure components are precise, reproducible, and suitable for stringent regulatory requirements.

 

LSR vs. HCR: Choosing the right elastomer

Selecting the appropriate elastomer requires understanding the distinct advantages of LSR and HCR (High Consistency Rubber). Both materials offer durability, flexibility, and biocompatibility, but their characteristics and suitability for different methods vary.

Matching the compound to your project’s volume, geometry, and functional requirements helps ensure consistent, high-grade results.

 

Understanding your options

LSR and HCR are made to address different demands.

LSR is designed for high-volume work where precision, repeatability, and automation are essential; meanwhile, HCR is better suited for specialized parts, larger components, or lower-volume runs, where compression or transfer molding delivers efficiency without sacrificing results.

Recognizing these differences early in the design helps guide materials selection and prevents downstream issues.

 

When LSR excels: High-volume precision manufacturing

This material is ideal for work requiring tight tolerances and consistent results across large runs.

• It excels in silicone injection molding, supporting rapid curing and automated workflows.
• Its dimensional stability ensures components meet strict tolerances, essential for medical devices and other regulated sectors.
• ProMed’s equipment, capable of handling loads from 11 to 240 tons, delivers repeatable precision across all production runs.
• This material is the preferred choice for projects producing several thousand parts or more, where uniformity and accuracy cannot be compromised.

 

When to pick HCR: Specialized performance needs

HCR is optimal for work that demands unique characteristics or flexible fabrication approaches.

• Its higher viscosity and compatibility with compression and transfer molding methods make it suitable for larger parts or lower-volume runs.
• It provides consistent mechanical properties for designs that may exceed the capabilities of LSR.
• Certain long-term implantable devices benefit from its durability and stability under extended use.
• Selecting it allows teams to optimize functionality, part size, and efficiency without compromising component precision.

That said, ProMed has substantial expertise in the injection molding of HCRs.

 

Choosing the right LSR formulation for critical applications

Material selection plays a central role in producing high-performing components for demanding work, including medical devices, aerospace, and other precision industries.

The right formulation ensures components deliver consistent biocompatibility, durability, and functional reliability while meeting regulatory and design requirements. Selecting correctly early on in development helps prevent costly redesigns and supports reliable outcomes.

 

High-performance LSR options for specialized components

ProMed provides a range of formulations and materials tailored to meet the needs of complex, tight-tolerance designs. Each process and material combination is engineered for specific performance requirements while supporting reproducible, high-grade molding results.

• Medical-grade silicone provides biocompatibility and passes cytotoxicity testing, making it suitable for devices that contact patients.
• Implant-grade formulations are designed for long-term implantable components, ensuring enhanced biocompatibility and stability over time.
• Optical-grade options offer high clarity, ideal for diagnostic windows and light-guiding uses.
• Specialty versions include conductive varieties and self-lubricating options to support unique or technically demanding designs.

ProMed oversees selection, testing coordination, and regulatory documentation for every formulation, delivering reliable, compliant, and high-performing silicone products.

 

In-house tooling: ProMed’s integrated design and manufacturing advantage

Designing and fabricating molds for silicone components is complex, but ProMed’s in-house tooling capabilities give it a distinct advantage. A dedicated team uses CNC machining and EDM to create intricate geometries, select appropriate tool steels, and integrate precise temperature control for consistent results.

Tooling options range from single-cavity prototypes to multi-cavity automated cells, supporting both low- and high-volume production work. Mold-specific features, including precision venting and flashless operation, ensure smooth, repeatable processes.

This integrated approach streamlines communication, shortens lead times for design adjustments, and strengthens oversight. Having the same team handle both tooling and fabrication preserves critical knowledge, maintaining consistency and reliability across every part.

 

Quality assurance: How ProMed prevents defects and ensures compliance

At ProMed, verification is integrated into every step of the molding process.

Our approach combines rigorous management systems (QMS) with controls and real-time monitoring to prevent defects and maintain compliance. By managing each stage with precision, we deliver components that meet the exacting standards of medical and regulated sectors.

 

Employing a comprehensive QMS

We prevent common molding issues through structured oversight and adherence to industry standards. Our QMS ensures consistency, minimizes variability, and supports full compliance with regulatory requirements, including ISO 13485 and FDA guidelines.

 

Preventing common issues through process excellence

ProMed applies scientific molding principles to avoid defects such as flash, voids, incomplete fills, and surface imperfections. This includes:

• Maintaining precise control of injection pressure, temperature, and cure time
• Ensuring accurate metering for consistent part properties
• Optimizing mold design with proper venting and gate placement
• Using over 35 years of experience for fast and effective troubleshooting

 

Cleanroom manufacturing for medical device compliance

All components are produced in ProMed’s Class 7 cleanrooms, which cover over 134,000 sq. ft. of controlled space. Strict monitoring of environmental factors, including particle counts and temperature, maintains the highest level of part purity.

Regular audits and comprehensive documentation uphold compliance with regulatory standards and produce comprehensive records for medical device manufacturers. This integrated approach ensures every component leaving our facility meets regulatory requirements, providing defect-free, fully compliant parts ready for use.

 

Partnering with ProMed: Your path from concept to production

Partnering with ProMed begins a collaborative journey from concept to full-scale production runs. Our team brings over 30 years of experience in medical-grade silicone molding, ensuring your products benefit from deep technical expertise and reliable processes.

Your partnership with ProMed includes:

• Guidance on initial consultation and materials selection to optimize functionality and compliance
• In-house design and fabrication of tooling to support precision and scalability
• Scalable processes, ranging from low-volume prototypes to high-volume automated production
• Ongoing verification that maintains strict regulatory and functional standards

With ProMed, every stage of your project is executed with precision, reliability, and regulatory confidence, giving your team a trusted partner for high-grade service.

 

Frequently asked questions:

 

1)  What is liquid silicone rubber (LSR) and why is it used in medical devices?

Liquid Silicone Rubber is a two-part, platinum-cured elastomer known for its biocompatibility, chemical stability, and temperature resistance. Its low viscosity allows it to flow easily into molds, enabling the fabrication of intricate geometries with tight tolerances.

In medical devices, it is used for components that require sterilization, long-term reliability, and consistent functionality. Examples include implantable devices, drug-delivery systems, surgical components, and precision seals. Its flexibility, chemical stability, and electrical insulation characteristics make it ideal for high-performing, regulated work.

 

2)  What certifications does ProMed Molding have for medical device manufacturing?

ProMed Molding holds ISO 13485 certification, FDA registration, and ITAR compliance. These credentials demonstrate strict adherence to standards across medical silicone molding, combination drug-device work, and regulated processes.

Certifications cover handling, tooling, molding, cleanroom operations, and documentation. They enable ProMed to produce validated, compliant components suitable for implantable and non-implantable devices, while also supporting submission-ready regulatory documentation for clients.

 

3)  What is the difference between LSR and HCR silicone molding?

LSR is a low-viscosity, two-part compound optimized for high-volume injection molding. It provides precision, reproducibility, and automation, making it ideal for small, complex, or high-tolerance components.

HCR is a gum-like, single-component option processed through alternative methods. It is better suited for larger parts or specialized needs. ProMed’s dual capability allows selection based on part size, volume, hardness, and regulatory requirements, ensuring optimal results and manufacturability.

 

4)  How long does LSR tooling and manufacturing take at ProMed?

Tooling and processing timelines vary depending on part complexity and material selection. Aluminum tooling typically requires 1 to 2 weeks, while steel tooling can take 3 to 6 weeks.

Once tooling is complete, sample parts are available within days. Full-scale timelines depend on volume, part geometry, and validation. ProMed’s integrated capabilities help streamline the workflow, allowing a smooth transition from prototyping to validated production runs while maintaining regulatory compliance.

 

5)  Can LSR parts be sterilized, and which methods are compatible?

Components can be sterilized using multiple methods commonly employed in medical and pharmaceutical work. These include steam autoclaving, ethylene oxide (ETO), gamma irradiation, and e-beam sterilization.

This compound maintains dimensional integrity, mechanical properties, and biocompatibility after sterilization. ProMed can guide materials selection and validate processes to ensure compatibility with the intended sterilization method, supporting safe and compliant fabrication of medical devices.

 

6)  What durometer should I choose for my application?

Durometer selection depends on functional requirements such as flexibility, load resistance, sealing, or mechanical support. ProMed offers silicone in durometers ranging from 10 to 80, covering soft, flexible parts to more rigid components.

Selecting the correct durometer ensures proper functionality under mechanical stress, sterilization, and environmental exposure. ProMed engineers can help evaluate durometer options to balance tactile feel, resilience, and regulatory requirements for your specific use.

 

7)  What size range can ProMed manufacture with LSR molding?

ProMed can manufacture components from micro-scale parts for minimally invasive devices to larger components for combination drug-device systems.

Injection volumes range from 1/50 of one gram to over 180 grams, accommodating low-volume prototyping and high-volume production. This range allows precise work with tight tolerances while scaling efficiently for larger projects.

 

8)  Does ProMed offer cleanroom manufacturing for medical devices?

ProMed produces components in ISO Class 7 cleanrooms spanning over 134,000 sq ft. Environmental conditions, including particle counts, temperature, and humidity, are continuously monitored to ensure cleanliness.

These controlled conditions ensure components meet stringent regulatory requirements for implantable and non-implantable devices. Cleanroom processing, combined with validated procedures, supports reliable, compliant work and submission-ready documentation.

 

9)  What secondary operations does ProMed provide for LSR parts?

ProMed provides secondary operations to prepare components for final assembly or use. These include post-curing, overmolding, manual deflashing, cryo-deflashing, assembly integration, and the coordination of specialized outsourced operations.

Each operation is performed under controlled conditions to maintain dimensional integrity, biocompatibility, and sterility requirements. Handling these processes in-house ensures consistent precision across all components and reduces risks in assembly or final use.

 

10)  How does ProMed support FDA submissions and regulatory approvals?

ProMed supports regulatory compliance by documenting properties, validations (IQ/OQ/PQ), biocompatibility testing, and sterilization validation.

Traceable records and documentation are prepared to align with FDA and ISO 13485 requirements, helping clients streamline submissions and approvals. This structured approach ensures components meet regulatory standards while maintaining reliability and functionality in critical work.

 

Conclusion

LSR manufacturing is a precise, detail-driven process where every stage — including formulation, molding, and verification — directly influences reliability and regulatory compliance. ProMed combines in-house tooling, robust systems, and extensive experience in regulated work to produce consistent, high-performing components that meet the stringent standards of medical, pharmaceutical, and aerospace & security markets.

Partnering with ProMed ensures a smooth, well-managed process that delivers durable, compliant products for demanding applications. Reach out today to discuss a project and explore how expertise can support the successful fabrication of high-grade, validated parts.

 

 

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