Numerical study on the influence of gas flow rates on the gas-assisted extrusion deformation of plastic micro-tubes

Abstract

In this paper, the effects of flow rate of assisted gases on the gas-assisted extrusion forming of plastic micro-tube were numerically investigated by using the finite element software Polyflow. Three phases fluid model was established and same volume flow rate was imposed on the inlet face of melt, different flow rate of inner and outer assisted gases were imposed on the inlet faces of two layers of assisted gases. Giesekus constitutive model was used to describe the rheological properties of melt. Numerical results show that with the increase of inner assisted gas’s flow rate, the inner and outer diameter will exponentially increase, that is, the inner cavity becomes bigger and bigger. When excessive flow rate of inner assisted gases is imposed, the inner cavity will be blown and broken. On the other hand, with the increase of the flow rate of outer assisted gas, the inner cavity shrinkage becomes more and more serious. The inner gas-assisted extrusion will be failed at the time of excessive flow rate of outer assisted gas imposed on the inlet face of outer assisted gas layer. Therefore, the reasonable controlling flow rates of inner and outer assisted gases are very important in the practice.