This guide to the process of reaction injection molding will help you determine if the popular and advantageous molding method is suited to your application.
Reaction injection molding (RIM) is a type of popular part molding process for producing large, complex parts in lower volumes. This unique process offers several benefits, such as lower tooling costs, sophisticated aesthetics, and unparalleled design freedom. If you are interested in utilizing RIM as your part production method, continue reading to learn more about the process of reaction injection molding.
Liquid Polymers Are Mixed Together
The process of reaction injection molding begins by mixing two liquid polymers together. The liquid polymers used in the process are known as polyol and isocyanate. These polymers are dispensed from their storage tanks into a multi-stream mixhead by high-pressure industrial pumps and then recirculated back into their storage tanks in a continuous loop.
The Mixture Is Injected Into an Aluminum Tool
Once blended together, the polyol and isocyanate create a low-viscosity mixture. This mixture is then injected into a heated mold. Because the mixture has a low viscosity, it does not require extremely high temperatures or pressures in order to get the material to fit the tool.
As such, the mold is typically made from low-cost aluminum rather than expensive steel which is required for many other molding processes such as injection molding. Thus, opting for RIM over other methods can greatly lower tooling costs and is often highly economically beneficial when creating parts in smaller production volumes.
The Chemical Reaction Takes Place
After the polymer mixture is injected into the aluminum mold, a heat-generating chemical reaction will take place. The reaction will cause the mixture to expand and fill the space of the mold. Upon doing so, the material will quickly harden. Curing times for reaction injection molded parts can range anywhere from a few seconds to several minutes, depending on a variety of factors such as the part’s size, wall thickness, and geometry.
The Finished Part Is Removed From the Tool
Once the polymer mixture hardens inside of the mold, it is ready to be removed. RIM generally has very short demolding times in comparison to other processes. Once the part is demolded, the reaction injection molding process can immediately begin again.
