Volumetric dosers are adaptable to auto-proportion mixing of new materials, regrinds, masterbatch or additives, adaptable to injection, extrusion or blow molding field. A stepper motor is used in this series, according to the set mixing proportion, the microprocessor accurately controls rotation of the high precise dosing screw to squeeze out materials with an deviation of ±1%. This volumetric doser can connect with various molding machine signals in synchronicity, to ensure the stability of the products.