Custom Gaskets

Molded LSR

2-part, platinum cured LSR molded to 3D and custom geometries

Small red and blue LSR molded parts with risen pegs and other micro gaskets with bumpouts for fit

Stockwell Elastomerics utilizes liquid injection molding (LIM) using liquid silicone rubber (LSR) to manufacture molded silicone parts, gaskets, sheets and rolls. Utilizing its extensive experience with LIM and LSR, Stockwell Elastomerics has selected the top performing liquid silicone rubber materials and processes for these custom components. LSRs are injection molded with faster cure cycles than gum base silicones. LSR components are UV and ozone resistant and have excellent water sealing properties. Liquid silicones can be molded into intricate parts with thin or thick cross sections, or into 12″ x 12″ sheets.

Request a Free Liquid Silicone Rubber Touch Brochure

Includes small samples of cured LSR materials to touch and feel.

Benefits of Liquid Injection Molding (LIM)

Faster cure cycles are a key benefit for specifying LSR for molded gaskets and seals. Cure cycles of 30 to 60 seconds are typical for small gaskets and cushioning components with thin cross-sections. This means a single or two cavity liquid injection mold can out-produce a multi-cavity compression mold due to the 6 to 8 minute cure cycles that are typical of gum base silicones. Fewer cavities in the liquid silicone mold can improve tooling lead times and improve dimensional consistency.

Benefits of Liquid Silicone Rubber (LSR)

Stockwell Elastomerics uses platinum cure silicone compounds to make injection molded parts and sheets. Some key features that make LSR the material of choice for many applications include:

Wide hardness range of 10 to 80 durometer Shore A
Wide operating temperature (-58°F to 392°F)
Good elongation properties
Excellent electrical insulation
Excellent UV and ozone resistance
Excellent for outdoor environmental sealing
Good for submerged sealing uses (IP67 and NEMA 6)
Materials include LSR with UL flame ratings UL 94HB and UL 94V-0
Excellent choice for medical devices
Certain products meet FDA and USP Class VI requirements
Good material for low temperature cushioning (cold drop test)
Many available standard colors and custom colors for molded parts and molded sheets

Silicone Injection Molding Tooling Costs

Tooling for injection molding of liquid silicone rubber components generally costs less than tooling for thermoplastic injection molding. Tooling costs will vary depending on size and part detail. To offer a sense of the cost magnitude – a mold for a seal approximately 4″ x 6″ with a .062″ diameter O-ring cross section may cost $1500 for a single cavity and $2000 for a two cavity silicone injection mold. A mold for a complex gasket with undercuts and complex geometry may cost as much as $6000 to $7500 for a single cavity mold.

Cost Savings Potential – Transition from Die Cutting or Water Jet Cutting to Molding for 2D Silicone Parts

Some manufacturing for flat, 2 dimensional silicone gaskets can be transitioned to a liquid injection molded gasket as production quantities increase. For example, a .125″ thick x 8″ x 10″, 20 durometer liquid silicone die cut or water jet cut gasket will cost about $15 each in start up quantities, but the center and edge material waste yielded from the cutting process limits the extent of further cost savings as quantities increase. If this gasket is “tooled up” in a single cavity injection mold, the unit price will drop in cost significantly (in production quantities) with a single cavity mold cost of approximately $3500 – $7500. The pay back for tooling this up can be achieved rather quickly.

Cost Savings Potential – Using LSR from Prototyping to Production

Another cost saving opportunity using molded LSR comes from prototyping from flat sheets and then transitioning later to molding using the same material. This means that as a customer’s design develops, any sort of material testing and validation associated with the initial quick-turn prototypes cut from LSR sheets does not have to be performed again if a switch to molding is made. Customers can take advantage of this by validating and testing LSR in flat sheet format before investing in tooling and large quantity production – this offers a cost-effective, low-risk, and timely solution when looking to validate an LSR for a specific application.

2D Prototyping for Silicone Molded Parts

There is an opportunity to prototype flat silicone rubber gaskets using water jet cutting. Sheet silicone materials are generally available in 10 through 70 durometer shore A in thicknesses ranging from .032″ to .250″ thick. Although the availability of specific hardness / thickness combinations will vary, by sending a solid model or 2D CAD file of your concept gasket with preferred hardness and thickness, a working prototype can be made and sent within a few days.

Molded LSR Sheets for Waterjet Cut Prototypes

Stockwell Elastomerics makes 12″ x 12″ sheets .020″ through .250″ thick, with custom non-standard thicknesses also available. The same compounds used to make custom geometries are used to make sheets in 10 to 70 durometer (Shore A). This special capability combined with four in-house water jet cutters allows Stockwell Elastomerics to provide custom liquid silicone rubber parts exceptionally fast to support requirements for limited production and prototypes where timing is critical. This capability takes sheet molding to water jet cut gasket in-hand in days instead of weeks.

Liquid Silicone Rubber in Continuous Rolls

Liquid silicone molding compounds can also be cast into thin silicone sheet materials, resembling latex in its consistency and elongation properties. Stockwell Elastomerics has teamed up with Rogers’ BISCO™ materials unit to provide 10 through 40 durometer liquid silicone rubber sheet in .010″ through .062″ thick in the form of silicone rubber gaskets. View availability chart / data sheets for these materials.