Numerical Simulation And Mold Design Of Polymer Pipe Gas-assisted Extrusion

Due to its advantages like low density, good chemical resistance, low resistance loss, and low cost, Polymer pipe has been widely applied in areas such as architecture, transportation, and fishery in China. However, because of the die swell, stress concentration and crack of external surface of products through pipe traditional extrusion, we applied the gas assisted extrusion technology into it. Forming a stable gas layer at the contact surfaces of the wall and the melt to eliminate the frictional resistance and perfect the flow form of the melt thoroughly. We used gas-assisted technology into pipe extrusion and conducted numerical simulation and mold design of polymer pipe gas assisted extrusion, on the base of analyzing of pipe and gas-assisted extrusion technologies. The main work is as follows:1、Simplified the basic equation of hydromechanics based on the flow form, choose PTT basic equation and used Polyflow to conducted numerical simulation to HDPE.2、Analyzed the field distribution, in or out of the mold, such as velocity field, pressure field, stress field and shear rate, etc. It was concluded that the non-slip adhesive shear mode between auxiliary gas layer and the melt can basically eliminate pipe extrusion swelling and deformation, and there are other important conclusions.3、Discussed the impact of technological parameter and physical parameter acting on pipe gas assisted extrusion. especially focused on its extrusion swell and field trend when changing the mold size. Found the reasonable gas-assisted length, and provided theoretical foundation for variety of gas-assisted extrusion pipes both in size and type.4、Pumped in assisted gas through gap method and designed the detailed mold, aiming at the pipe in such a parameter: inside radius R=10mm,wall thickness a=2mm.