Abstract: A numerical method to simulate surface tension in the micro circle extrusion flow has been developed based on software Polyflow. It showed that the surface tension becomes a more important role as the dimension of the extrusion die becomes smaller. As the surface tension coefficient increased, the extrudate swelling ratio, the meltpressure at the exit and entrances of the die, and the negative pressure of free surface at exit all increased. As the contact angle increased, the negative pressure of free surface at exit increased first and then reduced, with the first two parameters decreased.

Key words: surface tension, micro extrusion, contact angle, extrusion swelling