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Aerospace & Defense Molding 24 Nov 2025

Cast Urethane Molding

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updates@lform.com

How Does Cast Urethane Molding Work?

01 Create a Master Pattern

A master pattern is designed using CAD software. The master pattern is created using CNC machining or stereolithography (SLA), a form of 3D printing. The master pattern is then placed in a mold box and liquid silicone is poured around it to form a mold. After the silicone mold has fully cured, it is halved and the master pattern is removed. The cavity left behind is what is used for casting.

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02 Casting the Urethane Part

Mix the two parts of the liquid urethane resin together with any additives or pigments. Degas the mixture in a vacuum to remove any trapped air bubbles. Then the mixture is poured into the silicone mold.. It is then placed in a vacuum chamber, which helps remove air bubbles from the urethane and ensures a clear and bubble-free part. The completed part is removed from the mold and the process is repeated.

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03 Post-Processing

Trim any excess material (flashing) from the part. Urethane parts can be painted and a variety of textures and finishes can also be apple dto meet a variety of cosmetic needs. Urethane parts can be post-machined to achieve tight tolerances and can accommodate inserts. Urethane casting process is an excellent way to make small quantities of parts quickly for functional and cosmetic testing and accelerate your prototyping process.

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Advantages & Disadvantages of Cast Urethane Molding

Advantages

  • Cost-Effective For Prototyping & Low-Volume Production

    Silicone molds are significantly cheaper to produce than metal injection molds. That makes them a cost-effective option for low-volume production and prototyping prior to investing in tooling for injection molding.

  • Fast Turnaround Time

    Cast urethane molding has rapid lead times, with molds that can be created in weeks rather than the months. This enables you to rapidly iterate part designs and bring your new products to market faster.

  • Material Versatility

    A wide range of urethane materials can be used to produce parts that are soft and flexible or rigid and impact-resistant.

  • Complex Geometries

    Cast urethane molding can create intricate features, such as fine details, ribs, and undercuts, that are difficult or impossible to achieve with other methods like injection molding.

  • Test Multiple Hardness Levels from a Single Mold

    One silicone mold can be used to produce the same part in a variety of durometers, so they can be tested side-by-side to determine which one works best.

Disadvantages

  • Lead Time

    It takes an average of two weeks for silicone tooling to be created. Once it’s done, however, parts can be produced quickly.

  • Labor Intensive

    Cast urethane molding requires manual labor. It isn’t suitable to automation, which increases the cost per part.

  • Silicone tooling can only produce an average of 20-25 parts. After that, new tooling must be built to

    Short Tool Life produce additional castings. This also means that urethane casting isn’t practical for large-scale part production.

  • Limitations for Prototyping

    The silicone tooling used for urethane castings tends to lock engineers into a single design. New tools can be built to accommodate design changes, but each one takes an average of two weeks to build. If a part requires frequent design changes, it could become time-consuming to build new models and silicone tools for each variation.

  • Environmental Sensitivity

    Cast urethane parts tend to be sensitive to changes in temperature and humidity, which may cause the urethane to deteriorate.

Applications of Urethane Casting

Cast urethane molding is used across many industries for a wide range of applications,

Aerospace

The light weight of cast urethane parts make them a popular option for aircraft interior components. For spacecraft, heat shields and tooling components are sometimes made using this method.

Medical

Cast urethane’s versatility and low cost makes it a viable option for catheters, medical tubing, surgical drains, prosthetic limbs and handles for medical instruments.

Automotive

Cast urethane parts have found a surprising range of uses in today’s automobiles, including bumpers, door panels, dashboards, seats and suspension bushings and gaskets.

Electronics

The durability of cast urethane parts means they’re favored for electronic device casings and enclosures as well as to provide protective outer layers for components against abrasion and impact.

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What Can Urethane Casting be Paired With?

Overmolding enables designers to create parts with rigid and flexible parts, such as armrests and door handles, consumer products with two-tone designs and products with grippable surfaces. It’s also commonly used in the medical industry to create components that are easier to clean for use.

Polyurethane is easy to bond to other materials, such as plastic, metal and wood.

Traditional Technologies That Can Benefit from Urethane Casting

Many design engineers don’t realize that urethane casting is a viable and affordable alternative to producing small quantities of parts using injection molding. It produces parts with a surface finish and mechanical properties that are similar to injection-molded parts, making it ideal for late-stage prototyping and bridge production.

It’s also well-suited to parts with complex geometries and fine details.

Why Choose Fathom for Urethane Casting?

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