Investigation On Heat Transfer And Structure Optimization Of High Temperature Extrude Machinery

Based on digital models, additive manufacturing technique which is known as the typical technology of “ third industrial revolution”, creates a new physical objects through stacking the material layer by layer. Fused deposition modeling(FDM) is a kind of additive manufacturing technology, and the extrusion machine is one of the key components for it. Therefore, the research about the heat transfer character of extrusion machine not only can help to reduce the flow resistance of the material in the channel, but also optimize the structure of the extrusion machine and enhance the scope of material in the 3D printing device.According to the research of high temperature extrusion machine in large scale parallel 3D printing device, and considering that the new materials of Polyphenylene sulfone resin(PPSU) can't be applied to the piston of the extrusion machine,the study of new material PPSU and the design of extrusion machine is very necessary to carry out in this paper.The results show that, the viscosity of the PPSU in the molten decreases with the increase of shear rate, and the pseudo plastic behavior can be observed. At the same shear rate, the viscosity of PPSU decreases with the temperature increasing, and its flow is regarded as non-Newtonian fluid. The relationship between log ? and log ? with PPSU under different temperature conditions is approximate linear, and indicates its flow belongs to one of power-law fluids. The change process of specific heat capacity for PPSU is divided into two stages: the first phase is that the specific heat capacity of PPSU increases with the temperature and reaches to the maximum, and the variation approaches to be linear; for the second stage, after reaching its maximum, the specific heat capacity of PPSU decreases when the temperature continues to rise, and there emerges trough at the end of the measurement temperature range.Meanwhile, the heat loss of heated cavity in the load output heat is about 84%, so the whole thermal insulation can be applied on the heat cavity. In channel the static pressure is high, and the total pressure drop is large. The pressure drop of transition section and die segment are significantly decreasing in the channel, which accounted for 25.78% and 57.90% of the total pressure drop channel, respectively. The reason may be that, for the large viscous of PPSU, the pressure drop of the channel is mainly determined by the structure of die segment. Calculated from the theory, the heating power of high temperature extrusion machine is 20 W, the required theoretical torque 0.34 N.m, the thickness of insulation layer 0.065 m, theory melt length is 19 mm, and the best structure of the nozzle is that the angle is 60°and the diameter is 0.4mm.The design of high temperature extrusion machine, fully meet the requirements of PPSU in fused deposition technology, so it reaches the requirement of the design.