1. Context

During the manufacture of synthetic yarns and fibers (see for a detailed description of the various manufacturing processes), the polymer melt or solution is first pushed through a plate containing up to a hundred holes with a diameter close to a millimeter, through which the flow must be as uniform as possible. This plate and all the filter beds placed before it constitute the spin pack. After extrusion, these filaments are drawn simultaneously, to a greater or lesser extent depending on the process. Two processes with different industrial applications are considered in the following:

• Melt spinning. This high-speed spinning process is...