Polyurethane (PU) Casting

PU casting is also known as silicone rubber casting, or Room Temperature Vulcanization (RTV) casting. The mold material is silicone rubber and the cast material is PU.

The pattern for the mold is usually made by 3D printing or machining. One silicone rubber mold can cast 25-50 pieces of PU parts. The PU material consists of two parts in liquid form.

PU casting method is preferred over machining method in following scenarios:

• Lower the unit part cost when the volume increase;
• Make complex shapes that are not feasible by machining;
• Have special material requirements, such as transparency.

The PU casting process is ideal for low volume plastic parts. It saves clients from the higher cost and longer lead-time of production tooling. In addition, PU casting allows certain complex shapes that are not attainable by injection molding. The silicone rubber mold is soft so it allows large deformation when releasing the cast from the mold.

The following picture shows the mold and the cast. The part has a large special undercut that cannot be done by injection molding.