SRIM (Structural Reaction Injection Molding) has historically been a smart manufacturing choice for producing large economical parts that may have complex designs. SRIM is very important and under utilized by non-automotive product designers.
SRIM consists of a reinforced preform placed in a closed mold. The mold cavity is then filled with an impingement mixed resin that impregnates the reinforcement. The mold is filled with a runner system at low pressure, and reaction times are typically less than one minute.
The term structural in Structural Reaction Injection Molding has everything to do with the preform. The preform is a precursor to the finalized component, consisting of reinforcing fibers, core materials, and metal or plastic inserts. There is a lot of manufacturing freedom allowing different constructions. However the most common used material for the preform is fiberglass, due to its inherent low cost and performance. Different applications of the fiberglass have been used, including continuous strand mat, chopped glass, or woven cloth.