Cast iron or aluminum alloy. A sewing machine is a machine that uses one or more sewing threads to form one or more stitches on the sewing material to interweave or sew one or more layers of sewing material together. The sewing machine consists of four parts: machine head, machine base, transmission and accessories. The machine head of the sewing machine is made of cast iron or aluminum alloy through a casting process. The sewing machine casing is first obtained, and then the casing is processed into the machine head. In the early days of household sewing machines, they were basically single-needle, hand-operated sewing machines. Later, electric-driven sewing machines were invented and have become the mainstream in the market.