A premade mixture of chopped reinforcements, resins, and fillers is placed into a mold and cured under high heat and pressure.
Sheet molding compound (SMC) is compounded at an operation away from the press. A highly automated process of combining chopped fiber and resin matrices produces a semi-pliable sheet that is later used to mold a part.
Due to the stresses created by high tonnage pressing, typically only P20 steel is used to create two piece molds. Aluminum and other softer metals are utilized for prototype runs but have a significantly shorter useful life.
Compression molded parts can produce Class A finishes for decorative surfaces. They can be primed in the mold and can be delivered ready for a topcoat process.