Numerical Simulation And Die Design Of Gas-assisted Micro-tube Extrusion Process

With the development of micro-molding technology, people are no longer content to the goods of large size,instead,pursuiting the lighter,miniature and precise plastic products.In order to meet the needs of the ever-changing market,the plastics extrusion will develop towards these directions in the future.The proof is the significant momentum in the biological, medical, electrical, information,electronic industry and so on.The micro-tube extrusion this paper focused on belongs to the precision extrusion, which is increasingly wider used in the field of communication,medicine,space and so on. The medical catheters are the earlist and widest mico-tube products.This paper conducts a numerical simulation on the gas-assisted micro-tube extrusion process and designs a corresponding die.The primary items are as follows:(1)Import the 3D model built in gambit into polyflow. Based on Bird-Carreau constitutive equation, the numerical simulation of conventional and gas-assisted micro-tube extrusion processes was separately conducted.The results indicate that gas-assisted technology can almostly eliminate die swell,cut down the melt pressure by half and get the shear rate to zero in advance.(2)The influence of relaxation time,zero-shear viscosity,non-Newtonian index,wall slip and gas-assisted length on micro-tube extrusion is discussed by single factor analysis. The results indicate that ??0? ? n have different effects on conventional micro-tube extrusion but no effect on gas-assisted micro-tube extrusion.Smaller slipF is good to extrusion and gas-assisted length is advisable between 1 and 2 millimeter.(3)Through orthogonal test,effect degree of relaxation time,zero-shear viscosity,non-Newtonian index,wall slip and gas-assisted length on the crosssectional area of the micro-tube and the biggest pressure are analyzed respectively.(4)The effects of wall thickness and outside diameter on micro-tube extrusion were studied. Infiltrate the gas through porous metal and design a gas-assisted microtube extrusion die.