Tension is steady : Wrapping and take up tension keep constant from start to end;

Many factors affecting cell nucleation and cell growth among the extrusion process such as preshaping pressure, melt temperature, melt viscosity, interfacial tension, take-up speed and the te.

It is the function of the let - off motion to control the warp tension, so, to achieve the required result, both the take - up and the let - off motions must be functioning correctly.