Silicone Molding/Urethane Casting

At a Glance

Applications

Lead Time

Materials

Finishing Options

Low volume production, complex elastomeric parts, visual models, EVT units
10 days
ABS-like, Acrylic-like, Opaque Rubber, Clear Rubber
Custom textures, precise color match

About the Process

Silicone Molding (also known as RTV molding, Urethane Casting, and Vacuum Casting) is a fabrication method that uses silicone molds to produce production-quality parts, without the high costs and lead times of steel or aluminum tooling.
It is known for its fast production of high-quality prototypes or end-use products.

Silicone Molding production consists of three main steps:

1. Build a master pattern using 3D printing or CNC machining.
2. Build the mold by pouring platinum silicone around master.
3. Pour liquid polyurethane resin into mold, create polyurethane casting under vacuum.

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Why choose Silicone Molding

Silicone molding results in high-quality parts comparable to injection-molded components. This makes vacuum casted models especially suitable for fit and function testing, marketing purposes or a series of final parts in limited quantities. Vacuum Casting also lends itself well to a variety of finishing degrees, and we can match the finish you need for your parts.

Choose Silicone Molding for:

Choose a different process for:

High-accuracy functional parts from a wide range of engineering polyurethanes for pre-production runs
Low-cost visual prototypes for form and fit (choose FDM or SLA/DLP)
Cost-effective, low-volume production of end-use parts for volumes of 10 to 500 units
Production volumes greater than 500 units (choose Injection molding)
Isotropic parts with complex geometry not possible in CNC or Injection molding
Parts with tight tolerances and low surface roughness (choose CNC machining or Silicone Molding)
For complex elastomeric (rubber) parts not possible in injection molding

Materials

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ABS-like

A general-purpose opaque material that simulates ABS
thermoplastic. Good for most hardware product enclosures,
mechanical and functional parts.
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Acrylic-like

A stiff, transparent material for simulating acrylic
(PMMA). Good for see-through applications such
as light guides.
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Opaque Rubber

Simulates all kinds of rubber-like materials such as
TPE, TPU, and silicone rubber. Great for wearables,
gaskets, and overmolds. Available from Shore 20A
to Shore 90A in 10A increments.
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Clear Rubber

Simulates all kinds of rubber-like materials such as
TPE, TPU, and silicone rubber. Great for wearables,
gaskets, and overmolds. Available from Shore 20A
to Shore 90A in 10A increments.

Colors and Finishing Options

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Standard

Pigment is added to the liquid polyurethane prior to casting, so each casting has as-molded color. Customers may provide Pantone code for approximate color matching.
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Precise Color Match

Paint is recommended for parts that require exact color matching. Very light colors or specific shades of white may only be achievable with painting. Pantone code or sample swatch must be provided for precise color matching.
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Custom Textures

A variety of textures can be achieved by texture painting the master prior to mold making or by painting the parts after casting.

Technical Specifications

Standard Accuracy

Min Wall Thickness

Typical quantities

Surface structure

±0.3% (±0.3mm minimum)
1 mm minimum, recommended 1.5 mm
Up to 20 copies per mold (depending on the mold’s complexity and the casting materials)
High-quality surface finish comparable to injection molding