Research On Design And Extrusion Process Of Nylon PA6 Bar Extrusion Die

With the progress of society and the development of science,the varieties of engineering plastics are more and more diverse,and their applications are more and more extensive.The prepare and production of engineering plastics began in foreign countries.the development of engineering plastics were rapid in just a few decades and breakthroughs have been made every year from output to quality.Despite the large demand for engineering plastics in China,the proportion of self-produced upscale engineering plastics is still very low,in aspects of exploring the properties of engineering plastics,forming technology and mould technology are still relatively backward.Nylon PA6 is an important engineering plastics,which is widely used in automobile manufacturing,aerospace,household appliances and other fields.However,the fluidity of PA6 material is poor,it is sensitive to temperature in the process of forming and the range of forming temperature is very narrow.Aiming at the difficult extrusion forming problems of PA6 bar,the rheological design of extrusion die,manufacturing method,forming process and product quality analysis of PA6 bar were studied in depth.The primary items in this paper are as follows:Firstly,based on the theory of polymer rheology,the nylon PA6 bar extrusion die was designed and numerical analysis of molding process was carried out.The rheological properties of PA6 and the reasonable temperature range of extrusion were studied by capillary rheological experiments.The influence of structural parameters of runner in heating zone of PA6 extrusion die on melt temperature distribution and shear rate was studied by numerical analysis method.The structure of the cooling forming die was designed and the temperature distribution and cooling effect of the spiral cooling channel were analyzed by combining theoretical calculation with numerical analysis.Secondly,the single-chamber extrusion experiment of nylon PA6 bar was carried out and the optimal extrusion process was obtained through the experiment of bar extrusion.The forming quality of extruded bar products was analyzed.The results show that: The improved extrusion die structure and cooling forming system can reduce the craze on the surface of bar products,improve the mechanical properties,crystallinity and internal structure density of bar products,effectively improve the internal and external quality of formed products,which is of great significance for guiding the development of high-quality nylon PA6 bar extrusion die.Finally,the influence of runner structure on melt flow uniformity of six-cavity extrusion die for nylon PA6 bar was studied based on melt flow theory and computational fluid dynamics simulation method.The results show that: the radius of the straight section is the main factor affecting the melt flow uniformity,the length and spacing of the straight section mainly affect the melt flow rate in the inner channel 1 and the outer channel 3.The reasonable structure parameters of the six-cavity PA6 bar extrusion die were obtained,the numerical analysis results show that the pressure drop along the extrusion direction from the inlet of the main channel to the outlet of the shunt channels is similar,The volume flow rate of melt flowing through each shunt is equal.