High-Quality
Silicone & Urethane
Casting Parts

Parts in days anywhere in the USA.

Silicone & Urethane Casting offers:

Quality Matters  |  AS9100D Certified, ISO 9001:2015, ISO 13485:2016, & ITAR Registered

Certifications and Registrations

* Not all locations have all certifications and registrations. Parts requiring these will be made at facilities with the correct certifications and registrations.

Urethane & Silicone Casting
Table of Contents

What is silicone & urethane casting?

Silicone and urethane casting are commonly used to create replicas or reproductions of original objects or models. Silicone casting involves pouring a liquid silicone rubber material into a mold to create a highly detailed and flexible copy of the original object. This method is often utilized in the production of toys, prosthetics, or medical devices.

 

Urethane casting, on the other hand, utilizes a liquid resin material that hardens during the curing process, resulting in a durable and rigid copy of the original object. This method can be applied to various applications, including producing automotive and aerospace components, consumer products, and architectural models.

 

Both silicone and urethane casting require the creation of a mold of the original object before the casting material can be poured. The quality of the final product depends on the quality of the mold and the casting material used.

 

In summary, silicone and urethane casting are two effective methods for creating replicas or reproductions of original objects or models. Each method has its unique benefits and applications, and the quality of the final product is dependent on the quality of the mold and casting material used.

How does silicone & urethane casting work?

Silicone Casting

Silicone casting is a process used to create replicas or duplicates of an object or shape using a mold made from silicone rubber. The process involves several steps, including preparing the original, making a mold box, mixing and pouring silicone rubber into the mold box, waiting for it to cure, and demolding the final replica.

To begin, the original object is cleaned and prepared for the molding process. A mold box is created around the thing, usually made from wood or cardboard. Silicone rubber is mixed with a hardener, poured into the mold box, and cured for several hours or overnight. Once cured, the silicone mold is carefully removed from the mold box, and the original object is removed. Finally, the mold can be used to create replicas utilizing various materials, including liquid plastics and resins.

Urethane Casting

Whether you need multiple prototypes or are ready to jump into low-volume production, there are many advantages to using Cast Urethane. Cast urethane produces high-quality, precise, and consistent parts. The molds are low-cost and suitable for 20 – 25 reproductions. For larger production orders, we create more molds and maintain low prices for parts produced in the 100s. There is no need for expensive tooling. Cast Urethane is a relatively quick method. Once the CAD files for the master pattern are received, the products will be made and shipped in as little as three to ten days. The design flexibility is similar to injection molding, with a few exceptions. We’ll go into more detail below in the design guidelines section. We also offer a wide range of materials in our cast urethane department.

Types of Molds

We offer multiple in-house molds. Choosing the best one for your project depends on various factors. Here are some options:

Box Molds

Our most popular cast urethane mold is the box mold, created through a two-step process. In step one, the part is placed into a frame with clay on one side, and the cut line is determined based on where the clay is positioned. Silicone is then poured into the box, which is placed into a pressurized tank. Once the silicone hardens, the box is opened, and the clay is removed around the part. 

 

In step two, the same process is repeated, but this time, the clay is replaced with silicone. After completing this process, the master pattern can be removed, and end-use parts can be created.

Cut Molds

Creating the part involves gluing it to the gates and vents using cut molds. The mold and the part are then suspended in the frame, and silicone is poured around the piece. The frame with the material is placed in a pressurized tank. Once finished, the structure is removed from the material, and the cut lines are determined according to the location and geometry of the part. Creating a cut mold is faster in one day, but it can only be used for simpler parts.

3D Printed Molds

We can 3D print molds for silicone parts in-house. These molds are easy to remove the components from and can be re-used indefinitely, provided that heat is not introduced. Additionally, using 3D-printed molds eliminates the need for a master pattern.

Gravity Molds

Gravity molds are used for creating more complex parts that have locked-in features. The mold creation process is similar to that of a cut mold. The master pattern is suspended in the frame, and silicone is poured around it. Once the silicone is set in a pressurized tank, the box can be removed, and cut lines are created around the pieces. However, this process is very time-consuming, and the time required depends on the part’s complexity. 

 

The main difference between the gravity mold and the cut mold is that the former has no gates and vents. As a result, the end-use material can be poured directly into the mold.

Cast Urethane Mold line drawing

Designing Parts for Casting

When designing parts for silicone and cast urethane production, it is essential to consider the characteristics of the materials. Silicone is known for its flexibility, elasticity, and ability to withstand high temperatures, while cast urethane offers durability and abrasion resistance.

To design parts for silicone production, it is essential to ensure that the design will allow for easy demolding. This means avoiding undercuts or sharp corners that may cause tearing upon removal. Additionally, it is essential to allow for good material flow by incorporating fillets and draft angles.

It is essential to consider optimizing the design for the molding process for cast urethane. This includes ensuring an appropriate wall thickness, providing gates and runners for material flow, and utilizing a cavity that quickly removes the cast urethane part.

In both cases, it is essential to review the design with the manufacturer to ensure it suits the chosen material and production process.

Cast Urethane
Feature Recommended

Bosses

boss base: r = .25t
boss wall thickness: < 0.6t
inner corner fillet: 0.060 in

Drafts
3 - 5° reduces strain
Embossing

≥ 0.050 in between letters

Joints
include gap (0.025 - 0.080 in)
General Tolerances

± 0.010 or ± 0.003 per in (whichever is larger is typical)

0.15 % shrinkage due to thermal expansion

Radii & Fillets
0.25t or 0.125 in inside corners
Ribs

h = ≥ 3t
w = 40 - 60% of part's t
       ≥ 0.25t
draft angle: 0.25 - 0.5°
distance between: ≥ 2t
orientation: should all be in the same direction

Walls
recommended thickness: 0.040 in
feasible thickness: 0.020 in
the larger the part the thicker the walls

w (width)  |  d (depth)  |  r (radius)  |  in (inches)  |  ± (plus or minus)  |  > (greater than)  |  ≥ (greater than or equal to)  |  t (material thickness)

Cast Urethane
Feature Recommended

Bosses

boss base: r = .25t
boss wall thickness: < 0.6t
inner corner fillet: 1.5 mm

Drafts
3 - 5° reduces strain
Embossing

≥ 1.27 mm between letters

Joints
include gap (0.64 - 2.03 mm)
General Tolerances

± 0.25 or ± 0.076 per mm (whichever is larger is typical)

0.15 % shrinkage due to thermal expansion

Radii & Fillets
0.25t or 3.18 mm inside corners
Ribs

h = ≥ 3t
w = 40 - 60% of part's t
       ≥ 0.25t
draft angle: 0.25 - 0.5°
distance between: ≥ 2t
orientation: should all be in the same direction

Walls

recommended thickness: 1 mm
feasible thickness: 0.5 mm
the larger the part, the thicker the walls

w (width)  |  d (depth)  |  r (radius)  |  mm (millimeter)  |  ± (plus or minus)  |  > (greater than)  |  ≥ (greater than or equal to)  |  t (material thickness)

Silicone & Urethane Casting Finishes

Silicone and urethane casting finishes are coating materials that add a final layer of protection and aesthetic value to sculptures, model prototypes, and other resin-casted products. Silicone finishes come in two varieties: clear and pigmented. They are resistant to heat and chemicals, provide UV protection, and offer a glossy surface that accentuates the details of the product. On the other hand, Urethane finishes are available in various finishes, such as matte, gloss, or satin, and can be mixed to create a custom aesthetic. Urethane coatings also offer protection from UV rays, chemicals, and scratches while being more resilient than silicone finishes. Both silicone and urethane casting finishes require proper preparation, including removing mold-release agents and contaminants before application. In summary, choosing the right casting finish depends on the desired look and durability needed for the project.

Why choose Prototek for your next silicone or urethane casting project?

If you need silicone or urethane casting for your project, you should consider working with Prototek. Prototek offers high-quality casting services with a fast turnaround time. Our experienced team is skilled in creating molds and castings of various sizes, complexities, and purposes. We use advanced equipment and techniques to ensure precise and accurate results. Additionally, Prototek uses top-of-the-line materials to ensure their castings are durable, long-lasting, and withstand various conditions and environments. Furthermore, our team is committed to providing excellent customer service, and works closely with clients throughout the casting process to ensure that their needs and specifications are met. With Prototek, you can expect professional service and high-quality castings to complete your project needs.

What do our customers say about us?
They are competitively priced for their services and a very personable team to work with. If you haven't used them - do it! You'll have a lifelong vendor you be happy with that repeatedly goes above and beyond what is asked.
Product Designer
We are extremely happy with the quality of the parts as well as the level of service - thanks!
VP Product Designer