Thermoforming is to clamp the sheet on the frame and heat it to a softened state. Under the action of external force, make it close to the mold surface. After cooling and setting, the product is obtained. This method is also used for rubber processing. Compared with injection molding, it has It has the advantages of high production efficiency, less equipment investment and the ability to manufacture products with larger surface areas. The plastics used are mainly polystyrene. There are various molding methods for polyvinyl chloride, polyolefin, etc., which are combined or improved on the basis of three methods of vacuum, air pressure or mechanical pressure.