Effect of gas flow rate on the double gas-assisted extrusion forming of plastic pipes

Abstract

Abstract To overcome the extrusion problems of plastic pipes, the double gas-assisted extrusion method was used in this paper. To investigate the effect of gas flow rate on the double gas-assisted extrusion forming of the plastic pipes, the numerical simulations based on the finite element method were performed. Numerical results show that with the increase of the gases flow rate, the inner radius increases and the outer radius decreases, which lead to decrease the wall thickness of plastic pipes. At the same time, the flow velocity changes of melt under the different gases’ flow rate were obtained and compared. To ascertain the mechanisms of shrinkage phenomenon of wall thickness, the normal stress and first normal stress difference distribution nephograms of melt under the different gases flow rates were obtained. Results show that the normal stress effect of assisted gases on the melt is the main reason that the wall thickness is decreased by the larger assisted gases flow rates.