Quick-Turn Urethane Casting Production

Are you planning to have parts produced via injection molding but aren’t ready to commit to tooling yet? Urethane casting is an ideal way to produce small quantities of parts quickly for functional and cosmetic testing. Depending upon the part geometry and quantity of parts needed, it can also be faster and less expensive than additive manufacturing.

How Does Urethane Casting Work?

The urethane casting process is simple:

1. A master pattern is designed using 3D computer-aided design (CAD) software.
2. The master pattern is created using PolyJet or Stereolithography (SLA). Alternatively, it may be supplied by the client. (MB) most often we CNC the patterns actually. We will SLA them if complex.
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 completed part is removed from the mold and the process is repeated.

Applications of Urethane Casting

Common applications of urethane casting include:

• • Enclosures
  • Electronic device casings
  • Lower-volume manufacturing
  • Concept models
  • Marketing test samples
  • Bridge to production parts
  • Point of purchase displays
  • Conveyor systems
  • Medical devices
  • Specialty overmolding
  • Aircraft interior components
  • Soft, rubber-like parts

Industries where urethane parts are used include:

• • Automotive
  • Medical
  • Consumer products
  • Electronics
  • Medical devices

What Does Urethane Casting Make Possible?

Overmolding: It’s easy to mold an elastomeric urethane over a metal or plastic part to create a rigid product with a soft surface, such as an armrest. Another common application is press fitting and gluing inserts into urethane parts.

Greater design freedom than injection molding: Injection molded parts need to follow strict design rules, such as avoiding undercuts and thick-to-thin wall transitions, and designing draft into parts so they can be released from the tool. Because the silicone molds used in urethane casting are flexible, design engineers don’t need to worry as much about these rules and can design more complex features into their parts.

Clear parts: Urethane parts can be cast in a material that can be polished to a water-clear finish.

Flame retardant parts: One rigid urethane material is flame retardant. It’s hard to find additive materials with a UL94V0 rating.

Advantages 

Many finishing options: Urethane parts can be painted to match any Pantone color. A variety of textures and finishes are also available.

Exceptional detail: Urethane casting can be used to produce parts with complex geometries and fine detail.

Hard or soft: Urethane materials can be used to create both rigid and flexible, elastomer-like parts.

Fast to market: In the production range of 50-100 parts, urethane casting is often faster and less expensive than additive manufacturing. Whether you’re seeking bridge production or want to get consumer feedback on a new product, urethane casting can help you bring products to market faster.

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.

Short tool life: Silicone tooling can only produce an average of 20-25 parts. After that, new tooling must be built to produce additional castings. This also means that urethane casting isn’t practical for large-scale part production.

Limitations for prototyping: Additive manufacturing is ideal for rapid prototyping because it enables designers to quickly iterate a series of designs. In contrast, 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.

Impractical for 1-2 prototype parts: Compared to CNC machining or additive manufacturing, the cost to produce silicone tooling to produce one or two prototype urethane parts can be cost-prohibitive on a per-part basis. The sweet spot for producing urethane castings is in the 50-100 range.

Alternatives/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.

Alternatives to urethane casting:

For quantities larger than 200 parts, designers should look at other options, such as injection molding.

Traditional Technologies That Could 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.

Check Out These Urethane Parts 

Finishing Options for Urethane Parts 

The default finish for urethane parts is matte finish with no paint. Parts can be cast in color and will approximately match your specified Pantone color. However, paint is recommended for show models that require exact Pantone color matching for a better cosmetic result. Parts can also be cast to approximate a Mold-Tech MT-xxx texture.

In addition, urethane parts can be post-machined to achieve tight tolerances and can accommodate a variety of inserts.

Why choose Urethane Casting?

• It’s affordable. For low-volume production of parts, it’s often less expensive than injection molding or additive manufacturing.
• If you need to validate your part design and aren’t quite ready to invest in tooling, urethane casting can be used to quickly produce prototype parts that mimic the look and feel of injection molding.
• It can be used to produce parts with complex geometries that may be challenging to create using other manufacturing methods.
• It enables you to produce parts with a wide range of hardness – ideal for comparing different versions of the same part side-by-side.

Why Choose Fathom’s Urethane Casting Capabilities? 

You can benefit from Fathom’s technology-agnostic approach. We’ll start by having an engineer (not an algorithm) analyze your part design and understand its intended use as part of our detailed DFM process. We’ll then advise you on the best material and manufacturing solution to meet your requirements – whether that’s urethane casting, injection molding or CNC machining.

The Fathom team has extensive experience producing urethane castings. We can help you meet your cost, timing and performance requirements.

Fathom utilizes overseas partners to produce its urethane parts, which helps to keep them affordable.

Get a Urethane Casting Quote

Quickly get a quote on your urethane casting project today with our SmartQuote platform.

Additional Resources 

• • Fathom additive manufacturing services
  • 3D printing materials
  • 3D printing vs. injection molding
  • Design and engineering support
  • Rapid prototyping
  • Finishing and post-processing
  • U.S. plastic injection molding
  • China plastic injection molding