Computer Simulation Of Micro-Tube Extrusion Process

Today, medical technical has been more and more advanced, which has made a growingdemand for high-tech, high value-added medical micro-tube, and plastic micro-tubes hasgained more applications than rubber micro-tubes and metal micro-tubes in the medicalprofession,because some polymer materials have excellent biocompatibility performance,good mechanical properties, soft and good lubricity performance.Medical plastic micro-tubes are mainly produced by extrusion. We can obtained thespecific shape of micro-tubes by replacing other kinds of die based on the section shape ofmicro-tube we need, such as single-chamber, dual-chamber of different profiles, dual-holes ofdifferent diameter, even multi-cavity and so on. The extrusion of micro-tube is a verysophisticated process, precise debugging of the process parameters is the key of forminghigh-quality microtubes.At present, with the development of computer technology, the research of extrusionprocess has gradually shifted from the traditional method, that is, relying on experience torepeatedly repair and test the mode, to use CAE software simulating the extrusion process,which can calculate the flow circumstances of fluid within the die, the die swell after meltleaving the die, and the debugging scope of process parameter, etc. So if we put the actualextrusion process iteration on the computer virtual extrusion environment, we can greatlyreduce the human and financial resources, and moreover, can greatly increase the success rate.The temperature field of the cooling process has been simulated based on the theory ofheat transfer. A large-scale finite element fluid dynamics software POLYFLOW has been usedto simulate the flow channel of extrusion die, extrusion die swell and extrusion processingfactors. Then based on the goal, that is, to extrude expectation size micro-tubes (diameter1.6mm, wall thickness0.15mm), the matching process parameters have been explored, andfinally, micro-tube extrusion experimental was carried out to verified the simulation results.A large number of pre-tests have been carried out to study the impact law of the variousprocessing parameters on the extrusion process, furthermore, the test rheological phenomenonhas been analyzed theoretically, which laid the foundation for future research. In addition,based on the heat transfer theory and rheological theory, the temperature field of forming stereotypes cooling process has been numerically calculated, through which the temperaturedistribution in the die and the free cooling length have been gained.Then, the flow field of compression section and stereotype segment has been simulated,the theoretical model was amended based on the melt speed and pressure distribution in theextrusion process in order to determine the rational analysis model. The die-swell and gasexpansion of isothermal/non-isothermal have been simulated so as to judge the impact of heatexchanger of the melt and air on the swelling behavior, besides, the range of gas parameters inthe extrusion test has been gained.Finally, extrusion processing has been simulated. The processing parameters wasincluding wall slip, volume flow, injection gas pressure and traction speed, and their singleinfluence and combined effects on extrusion have been simulated, and the best matchingprocess parameters were explored in order to extrude the specific size micro-tube. Then theextrusion experiment has been carried out to verified the simulation result, and the deviationbetween the experiment and simulation results has been theoretical analyzed.