Effect of pressure bar in back drafting zone of SKF drafting system on spun yarn quality and optimizing drafting ratio

For improving the quality of spun yarn,the back draft ratios of SKF drafting system have to be changed when two pressure bars are fitted additively. When the back draft ratio is too low,the twisted roving cannot be sufficiently draft in the back drafting zone,resulting in thick places in the spun yarn.When the back draft ratio is too great,a drafting wave in the drafting roving is caused,and the quality of spun yarn is influenced.The effect of the back draft ratios in SKF drafting system on CV value,thin places,thick places,neps, strength and elongation of spun yarn were analyzed.The results of our investigations reveal that when the back draft ratio is 1.35 with roller setting of(51 mm),the optimum spinning conditions are obtained for the roving of(0.545 g/m) and 109 twist multipliers.