Research On Melt Pressure And Extrusion Characteristics In Vane Extruder

Both melt pressure and extrusion characteristics play an important role in evaluating the performance of an extruder,which have direct and important influence on processing efficiency and parts quality. A novel vane extruder that developed by Prof. Jin-ping Qu is totally different from traditional single screw extruder on the processing principle and structure. So the melt pressure and extrusion characteristics of them are also different. Researches on the vane extruder still stayed on the theoretical level and were incomplete so far. Therefore, the study on the melt pressure and extrusion characteristics will contribute to the optimization of the theoretical model. It also provides a powerful method to optimize the structure and processing parameters. The research results will promote the application of the positive displacement conveying method.The leakage between vane and stator bore can lead to many problems on melt pressure and extrusion characteristics. The interval in a vane unit was optimized by designing the non-circular bore on the stator, which reduced the leakage. The melt pressure characteristics in a vane unit were analyzed with finite element CFD analysis software POLYFLOW. The influence of structure parameters, processing parameters and material parameters on the melt pressure and extrusion characteristics has been experimentally studied on the vane extruder. And the melt pressure characteristics of non-circular bore were compared with that of circular bore. The numerical simulation results were also verified. The main results are listed as follows:(1)The numerical simulation results were consistent with the experimental results, and they showed that pulsating pressure changes homologous to sinusoidal with time in the vane unit. The pulsating frequency of melt pressure is four times of that of the rotor angular frequency when the number of vane is four. The pulsating amplitude of melt pressure increases with the increase of rotor speed, eccentricity and viscosity, but decreases with the increase of die pressure and axial distance to hopper. The decrease of viscosity, rise of die pressure and increase of axial distance to hopper would disorder the pulsation law.( 2) Compared with conventional single screw extruder, the vane extruder is characterized by positive displacement conveying. Therefore, the die pressure has little influence on the output, which means the tough extrusion characteristics.(3)The interval in a vane unit was optimized by designing the non-circular bore on the stator, which reduced the leakage. The plasticizing and conveying efficiency is improved by 7.5 percent. The pulsating amplitude of melt pressure in vane unit of non-circular bore is higher than that of circular bore.