Its extruder, cylinder and screw rods are made of quality alloy steel that have been nitrized and processed in a precision way. Hence it is sound in hardness, durable in corrosion resistance. The specially-designed screw is of sound quality in plasticizing, which helps increase the production capacity. It is applied to blowing the plastic films like low density polytene (LDPE), high density polytene(HDPE) and linear low density polytene (LLDPE). It is widely applied to producing the packing bags for foodstuff, clothing, rubbish bag and vest ones.