Winding core spun elastic yarns on cone bobbins to be dyed

摘要

Spiral yarn composed with an elastomeric filament DOW XLA, from Dow Chemical, and wool fibres outwardly wound around the elastic core presents a complex behaviour when wound on bobbins to be dyed. This article presents a basic mathematical model with the aim of evaluating radial pressure and transversal stress on bobbins at different angles of winding, different yarn tensions and yarn cross-section areas. Considering the additional complexities of the real problem, an experimental comparison of bobbin alterations under different conditions was carried out with the realisation of two experimental sets. The first experimental test bench allows the variation of winding tension, angle of winding and stroke, then experimental tests were carried out on a winding machine SAVTO varying the yarn tension value and adding a mechanical constrain to the device with the aim of reducing yarn-sliding phenomena, in particular during the thermal cycle. The fundamental parameters have been determined as the angle of wind and the yarn tension during the winding operation. Higher values of wind angle help keeping the bobbin shape. Higher values of yarn tension during winding operation allow the preservation of bobbin shape after the dyeing cycle. On the other hand, the upper limit is represented by yarn tensile strength. Moreover, it is not useful to apply a varying wind tension during the winding process.