On the structure of multi-thread boucle yarn
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This research had two dimensions. The first one was theoretical and the geometry of doubled fancy yarn, including bouclé yarn, was modelled mathematically. As a result, the length of the effect component that is necessary to make a copy of those types of fancy yarn was estimated. Further, a geometrical model for the width of the effectthread helices in the First Spinning Zone was presented. One important benefit of this model was using it to control the structure of the bouclé yarn and to prevent the formation of faults and loops on the bouclé yarns. The second dimension was experimental. The mathematical, geometrical model of doubled fancy yarn was tested and the coefficient of correlation between the predicted values and the actual values was r=0.90. This was accomplished by providing methods and roadmaps to help making copies of the bouclé and semi-bouclé fancy yarns after using the output of the geometrical model of the structure. Further, it was found that the technological factors which affected the bouclé yarn structure and geometry were the bending stiffness of the effect thread(s), the rotational speed of the hollow spindle, the level of Tension of the core thread, the overfeed ratio, the number of wraps, and the interaction between those factors. Furthermore, when narrow effect helices have formed in the First Spinning Zone, the thickness of the effect thread was as important as its bending stiffness. To measure the bending stiffness of the input threads, the Beam Method was applied using a simple apparatus, called the Bending Frame, which was built for this purpose.