Numerical Study on Effect of the Slippage on the Cross-Section Size and Profile for Inverse Extrusion Forming of Plastic Micro-Tubes

We studied the effect of slippage on the size and profile of outlet cross-section for the extrusion forming of plastic micro-tubes by means of finite element software Polyflow. The same material and process parameters were imposed on the established geometric model and mesh. The inverse extrusion forming method was used in the numerical simulation. The different slip coefficients were imposed on the surface of the inner and outer wall of plastic micro-tube. Numerical results show that with the increasing of the slip coefficient, the size of inner and outer diameter for the outlet cross-section is smaller and the profile is gradually distorted, which will increase the difficulty of the design and manufacture for the outlet cross-section of extrusion die. The filed distributions of melt with different slip coefficients were also obtained. The results show that the increasing of X flow velocity, nonuniform Z velocity and the increasing of the shear rate at the outlet face induced by the increasing of the slip coefficient are the main factors of changing the size and profile for the outlet cross-section of plastic micro-tube extrusion forming. (paper)