Analysis of the stabilizing effect of spinline cooling in melt spinning

Despite the fact that understanding of draw resonance in spinning process has steadily advanced with its onset readily predictable by the linear stability analysis method, as [C.J.S. Petrie, Progress Trends Rheol. II (1988) 9] eloquently elaborated, there are still many issues to be answered. For one, the stabilizing effect of spinline cooling has been proven by both experiments and the linear stability analysis but the question of why the cooling performs such a stabilizing role is not yet explained. The same can be said of other process conditions and material properties like elasticity over their roles in spinning stability. The governing physics and the hyperbolic nature of the spinning equations tell us that spinline tension represents the key link in relaying disturbances from the take-up to the spinneret to perpetuate draw resonance. In this simulation study the spinline tension sensitivity to disturbances has been found decreasing as the spinline cooling increases, i.e., stability enhanced by the cooling. This finding explains the success of an ingenious device called draw resonance eliminator of [P.J. Lucchesi, E.H. Roberts, S.J. Kurtz, Plast. Eng. 41 (1985) 87] which renders the spinline tension very insensitive to disturbances using maximum cooling air blown onto the spinline (the film in their case). It also explains why spinning with constant force boundary conditions is always stable by providing the reason that the transmission links between disturbances and the tension are completely disconnected in this case. Newtonian and upper convected Maxwell fluids have been tested to reveal that spinline cooling reduces the tension sensitivity to disturbances, resulting in increased stability.