Cross-section design of multi-lumen extrusion dies: study on the effects of die swell and gas flow rate of the lumen

In the paper, the effects of die swell and gas flow rate of polymer multi-lumen micro tubes on the design of the cross-section of the multi-lumen die are investigated mainly. On the one hand, the effects of die swell on the design of the cross-section of the extrusion die are studied on the basis of the function of die swell, extrusion velocity and length–diameter ratio of the die. After analysis, it is found that the die swell phenomenon is obvious especially when the micro tube is extruded with larger wall thickness at a higher extrusion velocity, which may lead to the deformation of the extruded tube. For extrusion of micro tubes with a well-defined shape, there is a need to optimize the geometries of the die accordingly to compensate this deformation. According to the analysis, a double-lumen and a five-lumen micro extrusion die are designed and manufactured separately. On the other hand, the extrusion experiments on the effects of gas flow rate of polymer multi-lumen micro tubes on the design of the cross-section of the multi-lumen die are conducted using the extrusion dies. Considering the effects of die swell and the gas flow rate of extrusion processes on the tubes, it is found that a well-defined multi-lumen micro tube can only be successfully fabricated by combining all the three factors including the effect of die swell, gas flow rate and optimization of the cross-section of the extrusion die.