Polyurethane (PU) can be molded in a variety of ways — open-cast, compression, spin cast and low-pressure injection. PU tooling is lower cost due to the simplicity of the tooling, the ability to gravity feed individual cavities, and the constant temperature processing, requiring no cooling lines.
Open Cast Molding - Because of the liquid nature of the uncured resin, PU parts are often molded using an open-cast process. The polymer and curative agents are premixed and poured into an open cavity of a mold. After the parts reach "green strength" or are partially cured, they are demolded and moved to a secondary post cure oven. Open-cast molded parts are subject to a looser tolerance on the open-cast surface and may require a secondary cutting or machining operation if a tighter tolerance is needed.
BRP- PU can be cast using a compression or closed mold process. The polymer and curative are premixed and poured into the open mold. The mold is overfilled with raw material, helping to drive out air as the mold is closed and placed under pressure. After the parts reach "green strength,” they are demolded and moved to a secondary post cure oven. In this process, all surfaces are controlled by the closed mold.
Spin Casting - The polymer and curative are premixed and poured into a spinning, closed mold. This process is designed to remove air that can be trapped during polyurethane casting. After the parts reach "green strength,” they are demolded and moved to a secondary post cure oven. Like the open cast urethane molding process, a secondary machining process may be needed to remove the risers or gates.
Low Pressure Injection Molding - In the polyurethane injection molding process, the polymer and curative are premixed and injected under low pressure into a closed mold. Bleeder vents are used to allow the excess air to escape during the injection process. After the parts reach "green strength,” they are demolded and moved to a secondary post cure oven.
Outstanding physical properties
Advantages over metal, rubber, and plastic
Wide range of part applications and industries
Compatibility to various polyurethane molding methods
Ability to be finished in numerous ways
Low to mid volume production
Diversity in part size