Melt pump belongs to positive displacement gear pump, adopt a pair of external gearing cylindrical gears(straight gear, helical gear, herringbone gear) with relative turning to deliver high viscosity fluid. All gears and fitting surfaces are accurate grinded, and obtain precision flow by controlling the assembling clearance strictly. Gear and pump body varies to different materials. ZB-B series are produced by nickel-chrome alloy steels and high temperature tool steels.