What factors are related to the leakage of the melt pump?
During the use of the melt pump, improper operation and operating conditions can cause leakage of the melt. Zhengzhou BATTE melt pump manufacturer analyzes the reasons for the leakage of the melt pump extrusion from the following four aspects.
1. Leakage gap.
The leakage of the gear end face is the main part of the total leakage amount. The radial leakage caused by the gap between the top of the gear and the melt pump body and the bearing gap accounts for a secondary proportion of the total leakage. The leakage caused by the gap between the tooth surfaces only accounts for a small portion of the total leakage and can be ignored.
The leakage caused by gaps set up to compensate for manufacturing tolerances, elastic deformation, thermal deformation, and melt lubricated bearings of various components is inevitable. Only by optimizing the design of each gap as much as possible and improving the manufacturing and processing accuracy of the extrusion melt pump can the leakage be limited.
melt pump extrusion
2. Melt viscosity.
For plastic melts that follow the flow characteristics of power-law fluids, the leakage rate is inversely proportional to the "effective" viscosity of the fluid in the gap. It is obvious that plastic melts with low viscosity are more prone to leakage than those with high viscosity. Therefore, relatively speaking, when transporting plastic melts with high viscosity, the volumetric efficiency of the melt pump is higher.
3. Operating process conditions.
The "effective" viscosity of the fluid in the gap is a function of the melt temperature and the shear rate of the fluid in the gap. On the one hand, the effective viscosity of the melt changes. As the temperature increases, the viscosity of the melt decreases and the leakage rate increases. On the other hand, the fluid shear rate in the gap is directly proportional to the gear speed, which affects the effective viscosity and leakage flow rate of the fluid in the gap, and has an impact on the volumetric efficiency of the melt pump.
hot melt pump
4. Pressure difference between inlet and outlet.
The magnitude of leakage is closely related to the pressure difference between the inlet and outlet of the hot melt pump. Under this pressure gradient, plastic melt leaks from the high-pressure zone to the low-pressure zone through channels formed by various gaps. For melts that follow the flow characteristics of power-law fluids: Pressure difference is a comprehensive parameter of multiple factors such as melt temperature, pump speed, and inlet flow rate.
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