Urethane parts are often cast in inexpensive, low-pressure molds. As a liquid, urethane can fill even complex mold cavities without high-pressure molds and presses. Especially during iterations of design, prototyping and testing, much of the delay and cost of re-tooling can be avoided, resulting in better products, sooner.
There are a variety of different types of materials that are used when creating a mold for casting polyurethane. The most common materials that are used include urethane, silicone, steel and aluminum. The determining factors that are considered when making the choice for which type of tooling material to use are price, aesthetic quality, quantity of parts to be produced and how tight the tolerance of the finished part needs to be.
The typical tolerance range for cast polyurethane parts is ± 0.015″ or ± 0.003″. Certain parts can be manufactured to a tolerance of ±.0005″, but that typically requires a secondary operation after the part is poured. Depending on the operation it could affect the aesthetics of the part. For example, grinding would produce a matte finish.
Polyurethane can be bonded to a variety of different materials, including certain types of plastics and most metals. This ability makes polyurethane an ideal material for an endless supply of possibilities.