Abstract: The extrusion of multi-lumen micro tube with small size, uneven thicknesses and complex section shape is difficult, so double-lumen micro tube with different cavity shapes is taken as the research object. A trace ventilation system is introduced to the extrusion process, and non-symmetric flow balance design method and fine electrical discharge machining(EDM) machining technology are used to design and manufacture the right angle extrusion die. Then, effects of extrusion process parameters on the shape accuracy of double-lumen micro tube, evaluated by the ellipticity of profiles and uniformity of wall thicknesses, are investigated experimentally, taking polypropylene as extrusion material. Experimental results show that the effects of gas flow rates, screw speed, die temperature, tank vacuum and drawing speed on the ellipticity of products weaken in order. However, the thickness uniformity of products depends mainly on the extrusion die, and it is hardly influenced by the changes in process parameters. Through the analysis of experimental results, the action mechanisms of the above process parameters on the product deformation are revealed. The optimum combination of process parameters is concluded, and double-lumen micro tubes which meet the design requirements are obtained.

Key words: Double-lumen micro tube, Extrusion process, Polymer, Right angle extrusion die, Shape accuracy