TIPS WITH TONY: LSR Offers Design Flexibility

There are many reasons why you should be looking at liquid silicone rubber (LSR) — I’ll highlight a few big ones in order to get you thinking about this versatile thermoset.

For a deeper dive into LSR and how it’s used in the lighting industry, please attend my free tech talk webinar hosted by Tech Briefs.

LSR Molding
LSR parts are formed in process similar to that of conventional plastic injection molding with one main difference. LSR is a thermoset material that compounds two liquids together, which is then heat cured in the mold to produce a part. The material delivery system is cooled and only the mold is heated. This is unlike thermoplastic molding, which begins with the melting of plastic pellets that are injected into a heated mold.

Optical LSR is highly flexible and can replace glass in many lighting applications.

LSR Advantages
LSR parts are strong, elastic, chemical resistant, serializable and biocompatible, and have a range of operating temperatures. The benefits of LSR lend itself well to the automotive, medical and lighting industries where gaskets, seals and lighting lenses are frequently used.

LSR parts have a very good temperature resistance, ranging between -49°F to 392°F; they are non-yellowing, UV stable and optical LSR has up to 94 percent light transmission; they offer good vibration control and offer up to 400 percent flexibility along with excellent part memory.

The chart pretty much speaks for itself when comparing LSR to PC, PMMA and glass when looking at replacing the traditional materials with LSR.

Design Flexibility
Traditional thinking of part design needs to be considered, but many can be broken:

  • Part thicknesses greater than 1 in. and less than 0.020 in. are achievable with little to no concern of any unsightly sinks or internal voids.
  • No ejector pins are used to remove parts from the mold as they are all hand-removed.
  • Gates are nearly invisible, barely thicker than flash. LSR flows like water, so the gate needs to be very shallow, but wide.
  • Negative draft angles or increased undercuts are a possibility with up to 400 percent part flexibility and part memory.
  • Ability to fill fine details or voids.
  • Ability to combine components reducing number of parts to assemble, e.g., combining a lens and seal for lighting applications.

For more information on LSR, please download our white paper or listen in to my tech talk presentation mentioned at the top of the tip. You can also visit our website at or contact one of our customer service engineers at or 877.479.3680 with additional questions on any of our services.

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About Tony Holtz

Tony is a technical specialist at Proto Labs with more than 10 years of experience ranging from CNC mill operator to mold designer to customer service engineer. While his formal education is in industrial machinery operations, he has extensive knowledge and experience in both traditional and advanced manufacturing processes and materials. Throughout his tenure at Proto Labs, Tony has worked with countless designers, engineers and product developers to improve the manufacturability of their parts.

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