Melt pump has a very good metering and pressurization, regulator function, which stems from its unique transport mechanism. The gear of the pump is rotated once a week, and the discharge is constant, so that the continuous discharge and measurement of the melt are carried out. The gears of the pump are quite a rotating barrier that can effectively block the pressure fluctuations in the feed zone and the effect of flow fluctuations on the discharge zone. When the pump outlet pressure due to fluctuations in various factors in a large range of changes, the pump outlet pressure fluctuations can be controlled in a very small range of changes. Due to the pressure isolation of the melt pump, the factors influencing the pressure and flow fluctuation in the discharge area of the pump are significantly reduced and easy to control, so that the flow rate of the output of the melt pump is stable and accurate.