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Urethane Casting Services

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Urethane Casting Services

Urethane Casting is most commonly used during the prototyping process and can generally be expected to hold +/- .010″ tolerances with +/-0.003 in/in (whichever is greater). For urethane casting equipment and parts with tight tolerance requirements, Fathom generally recommends CNC machining or injection molding. Regarding soft parts, there is a Shore A tolerance of +/-10. Please note, the above tolerances are not guaranteed because geometries vary and every application is different, so please speak directly with one of our urethane casting experts.

RTV Advantages:

  • Urethane casting is low cost compared to the tooling costs required for mass manufacturing.
  • RTV Tooling is more easily constructed than hard steel tools and can be easily modified.
  • Parts can be manufactured quickly to prove out your design before production.
  • Dyes can be mixed into the resin before casting, eliminating the need to paint parts.
  • Many material properties can be achieved, including rigid and flexible parts from 10 Shore A to 80 Shore D.

Soft Tool Casting Requires a master pattern and a silicone tool be made.
Master Patterns Usually CNC machined master patterns that last up to one year for most geometries, though masters can break during the making of the silicone tool. 3D printed (e.g. PolyJet or SLA) masters have a shorter shelf life. Masters are destroyed after their useful life.
3D Printed Tools Tools are good for up to 20 parts for most geometries and can deliver quality parts up to 90 days from being made—tools are destroyed after their useful life.
Overmold Complex parts such as overmolds can be achieved, however the urethane casting process does not result in a very strong chemical bond between shots, regardless of material selection. Parts should be designed to maximize mechanical bonding between shots.
Color Parts can be casted in color and will approximately match specified Pantone color, however, paint is recommended for show models (greater cosmetic result) and parts that require exact Pantone color matching.

Urethane Casting Parts and Images

How Does Urethane Casting Work?

The urethane casting process is as follows:

  1. Using 3D CAD software, a master pattern is designed.
  2. Using PolyJet 3D or stereolithography (SLA), the master pattern is created. Alternatively, the master pattern may be supplied by the client.
  3. The master pattern is then placed in liquid silicone to form a mold.
  4. 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.
  5. Urethane and other resin materials are added to the mold tool and cured.
  6. The process repeats.


The process enables designers and engineers to get production-like urethane casting material parts in their hands quickly, whether a company is in the midst of the prototyping phase of product development or need finished looking parts for final tests and presentations. We currently offer the materials listed here. If you need any assistance selecting the proper material for your project, please do not hesitate to contact us.

ABS-Like 85 D Can Be Colored for Near Match to Pantone Common Material Choice Cast Urethane Injection Molding
UL94V0 Rated 74 D UL94V0 Rated Material Meets Specified Flammability Standard
Polypropylene-Like 80 D
High Temp 80 D Light Tints are Very Difficult as Resin Is Naturally an Off White Glass Transition (Tg) at Over 120°C
Clear High Temp 87 D Clear Only Requires a High Polish to Achieve Water Clear Finish, Glass Transition (Tg) at 110°C
Silicone 30A-50A Can be Colored for Near Match to Pantone Cannot Paint, Food Grade Compression Molding or Liquid Silicone Injection Molding. Increased Range of Shore Values are Possible. Talk to an Expert Directly to Learn More.
Rubber-Like 30A-90A Cannot Paint Injection Molding, Compression Molding or Liquid Silicone Injection Molding
Clear Rubber-Like 30A-80A Clear, Can be Tinted to Achieve Transparency Clear, Cannot be Painted

Additional Notes // If color matching needs to be exact, Fathom often recommends doing a first article even though it will extend the timeline. If a color or assembly match needs to be made for other parts, a sample part is recommended to confirm color match. Parts can be molded in glossy or matte finish—please always specify. If Shore A needs to be exact, Fathom recommends a first article, as well as casting in a .25″ thick test slug for durometer measurement, which again,  may add to the timeline though this extra time investment will ensure accurate part delivery.

Need A Material Not Listed? Please Speak With A Fathom Expert Directly About Additional Material Options

Advantages of Urethane Casting

Before choosing urethane casting for your project, it is important to note the advantages.

Advantages of urethane casting include:

  • Different colors, textures and finishes may be used
  • Wide variety of material, both rigid and flexible options
  • Finer details can be accomplished
  • Varying wall thickness
  • Reduced lead times, faster to market
  • Higher level of detail than traditional manufacturing methods
  • Higher quality production parts at lower volumes
  • Accurate testingto ensure part accuracy before production
  • Casted part can include threaded inserts, adding strength to the part
  • 3D printed master patterns and silicone mold tooling

Common Applications of Urethane Casting

Many industries use urethane casting for their projects. For jobs that require a lower quantity, when the amount does not justify investing in injection mold tooling, or for use as a first production run, urethane casting can be a smart choice. Advanced prototyping is also feasible with urethane casting because the tooling and design changes cost less than with other manufacturing methods. It is also possible to test a variety of materials from a single mold. Parts made using urethane casting can also be used for customer testing. Still, a high quality, high performance and precise part can be produced. Many industries use urethane casting.

Some of these applications include:

  • Test prototypes
  • Rapid prototypes
  • Exhibit parts
  • Consumer testing
  • Products for crowdfunding
  • Lower-volume manufacturing
  • Concept models
  • Sales samples
  • Engineering models
  • Marketing test samples
  • Pre-production runs
  • Bridge to production
  • Point of purchase displays
  • Robotics
  • Conveyor systems
  • Printing
  • Medical devices
  • Specialty over-molding
  • Aircraft interior components

Urethane Casting vs. 3D Printing

Both urethane casting and 3D printing are popular manufacturing methods for producing a lower volume of parts. 3D printing is an additive manufacturing process that begins with a CAD design and then uses a machine to build the piece in layers. In urethane casting, the master mold is first produced, usually by a 3D printing method, then the mold is used to create a cavity of the product in silicone. Urethane or other liquid resin is poured into the cavity to form the part. When it comes to selecting a material, there are limitations with both methods. 3D printing does allow for a broader range of plastic and metal material. The material used for urethane casting is limited to rubber or plastic that will cure at room temperature. 3D printing is excellent for prototyping and intricate, iterative designs. Urethane casting is great for creating replicas. Each method has different capabilities and costs, each having its own unique advantage depending on a project’s needs.

Urethane Casting vs. Injection Molding

There are a number of differences between urethane casting and injection molding that may determine which method is best for your project. Injection molding is more expensive than urethane casting. Injection molding tooling can cost thousands to tens of thousands of dollars, whereas urethane casting costs rangle from hundreds to thousands. Injection molding uses a real plastic material, but urethane molding uses polyurethanes, which simulate the plastic used in injection molding. Both processes can be used for over-molding onto plastic or metal parts. One of the most substantial differences is volume; injection molding can be used to create a prototype, bridge and high-volume production in the thousands. Urethane casting is best for prototype, bridge and production parts in the hundreds.

Urethane Casting Questions Answered

Q: What is the maximum size for a urethane cast part?

A: Larger parts can be reviewed by the project to determine size capabilities.

Q: How many parts can you produce from a single mold?

A: On average, up to 25 parts. If the design includes many sharp edges, this may cause the mold to deteriorate more quickly.

Q: How is the silicone mold tool made?

A: First, a design is created using CAD software or a model is provided by the client. A 3D printed master model is created and then encased in silicone rubber. Once the silicone has cured, the master model is removed. The cavity left behind is the mold tool.

Q: Can urethane cast parts be used for final products?

A: Absolutely. While urethane casting is popular for rapid prototyping, this method can be used as a bridge tooling process to get the product to market for testing during simultaneous production tooling. It is also perfect for final products when the quantity needed is low to medium.

Q: Will I sacrifice appearance by choosing urethane casting?

A: No, Fathom will work with you to ensure your parts are of high quality.

Q: What is another term for urethane casting?

A: Urethane casting is sometimes referred to as urethane molding.

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From models to prototypes for short-run applications like product trials, urethane casting is a great way to fabricate a low volume of parts that accurately mimic the color, texture, feel  and other physical properties achieved if it was an injection molded part.

Comprehensive Capabilities for Rapid Manufacturing

At Fathom we offer a unique advantage of speed and agility-our experts help companies go from concept to prototype to manufacturing in ways not previously possible. 

3D Printing / Additive Manufacturing
90+ Machines  
SLS / / Two-day  SLA / / Next-day 
FDM / / Next-day DMLS / / Three-day 
PolyJet / / Same-day MJF / / Two-day
Injection Molding

30 Second Quotes

Prototype Tool / / As soon as 10 days

10K Parts / / 10 days

Production Tool / / As soon as 3 weeks

CNC Machining

3 & 5 Axis Milling & Turning
(Plastics, Composites and Metals)

Tolerance Accuracy Range
from +/-0.001″ to 0.005″

Urethane Casting

Injection Molding Adjacent
without High Costs of Metal Tools

Most Commonly Used for High-Volume
Prototyping & Bridge to Production

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Fathom is driven by advanced technologies and methods that enhance and accelerate today’s product development and production processes.