SMC (Sheet Molding Compound) is a ready-to-mold thermoset composite made of polyester (or vinyl ester) resin reinforced with chopped glass fiber — typically 20% to 25% by weight — and inert mineral fillers such as calcium carbonate. The heat-and-pressure compression process allows manufacturing complex, large-format parts in short and medium runs, with good dimensional stability, mechanical strength and standard electrical insulation, at no metal tooling cost.