Optical Liquid Silicone Rubber: A New Fixture in Molding

TIPS WITH TONY

Proto Labs offers many manufacturing processes and materials for prototype and production parts. But one process has a material that separates itself from the rest, optical liquid silicone rubber (OLSR). OLSR is an advanced material that has many properties that make it a preferred material choice over polycarbonate (PC) and acrylic (PMMA) for lighting and optical parts. Here are a few of the benefits that OLSR offers:

prototype lenses molded in liquid silicone rubber

Prototype lenses molded in liquid silicone rubber.

Light Transmission
Light transmission is lost as light passes through a material. PC, PMMA, and even glass will have light loss with glass retaining up to 95 percent, PMMA around 93 percent, and PC between 88 to 90 percent. When your product requires a clear PC or PMMA part, you can improve on light transmission using OLSR, which retains up to 94 percent light transmission.

How about the refractive index? OLSR has a low refractive index of 1.42 when compared to PC and PMMA, which are at 1.58 and 1.49 respectively.

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Still another advantage is the non-yellowing factor. Thermoplastics without additives are not UV resistant, which means the parts could yellow and degrade over long exposures to lights and sunlight. OLSR is non-yellowing so it’s great for outdoor fixtures exposed to harsh environments.

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WHITE PAPER: Aluminum Tooling for Optical Moldable Silicone

Dow Corning recently published a comprehensive white paper on the use of aluminum tooling for moldable optical silicone. It examines two big questions:

  1. To achieve a high-quality finish on the molded parts, what type of optical-grade surface finish is required for the tooling used to mold the silicone optics?
  2. Can this be achieved with an aluminum injection mold or is tool steel required to provide parts with an optical finish?

Proto Labs’ aluminum tooling is a reliable indicator of future optical silicone moldability.

Read why integrating optical silicone into your development cycle with rapid injection molding is an effective strategy, and why aluminum tooling is a reliable indicator of future moldability.

DOWNLOAD WHITE PAPER HERE.

Why use optical moldable silicone? It’s a relatively new material to the market, but it is quickly gaining popularity as a replacement for glass components in many optical and lighting applications. Its benefits include:

  • clarity
  • heat resistance
  • durability for use in outdoor and automotive applications
  • design flexibility for fine features
  • an ability to combine multiple parts into a single unit

Learn more about optical silicone with our “14 Reasons Why Optical LSR is Good for Lighting Applications” design tip.

Strategies in Light Underway in California

The big lighting and optics show, Strategies in Light, starts today in Santa Clara, California. We’ll be talking with designers and engineers over the next three days about how industrial 3D printing, machining and injection molding processes can help them develop well-designed, more efficient products and devices. Track us down at booth #102.

One topic that is certain to dominate the conversation is the relatively new thermoset material, optical liquid silicone rubber (LSR), which has many advantages during lighting development versus plastics like polycarbonate and acrylic.

Optical liquid silicone rubber prototype from automotive company MagWerks LED.

Optical LSR is changing the lighting industry with its superior material and optical properties that improve:

  • durability
  • lightweighting
  • heat resistance
  • UV stability
  • light transmission
In addition to ongoing optical LSR discussions in the booth, we’re co-hosting a presentation with Dow Corning on prototyping with optical moldable silicone on Wednesday, March 2 at 1 p.m. in the presentation theater. Proto Labs’ global segmentation manager Jeff Schipper and Dow Corning senior application engineer John Nelson will cover why optical LSR works well for prototyping and low-volume injection molding and the results of recent research on implementing aluminum versus steel tooling when molding with optical silicone.
We hope to see you at the show!

14 Reasons Why Optical LSR is Good for Lighting Applications

As LEDs increasingly supplant metal filaments in light bulbs, optical LSR — in addition to plastics like polycarbonate and acrylic resins — is replacing glass in many optical applications including lens covers and light pipes.

Optical LSR is a transparent, flexible thermoset material that is replacing glass in many optical applications.

The flexible, transparent material is second in clarity only to glass; it can withstand heat in proximity to high-output LEDs and operate in a range of ambient temperatures. Optical LSR is flexible enough for rough duty, outdoor and automotive use. It also allows for very flexible design including accurate replication of fine features. It can support minor undercuts and negative draft without the need for side-actions, and both thick and thin walls. Designs in this material can often integrate multiple parts into a single unit, combining for example a lens, a clear lens cover and a sealing gasket, reducing the bill of materials for a final assembly.

Proto Labs stocks Dow Corning MS-1002 LSR, a material that has been engineered for molding finely detailed parts for LED applications. Read our full Design Tip to see how optical LSR might help on your next lighting project.