Study of drafting force variability and sliver irregularity at the break draft zone of a draw frame

Abstract

To produce an evener fiber assembly, it is important to understand fiber dynamic behavior during the drafting process. Drafting force and its variability is an alternative approach to understand the fiber’s velocity–friction characteristics, representing a combined effect of multiple fiber properties. In this study, online drafting force and its variability was measured with different break draft ratios and back roller gauges to analyze its effect on sliver short-term evenness. Drafting force variability well correlated with sliver evenness with correlation coefficient R2 = 0.81. The coefficient of variation (CV%) of drafting force was highest (2.3%) at low break draft 1.1–1.2, and then reduced gradually to its minimum value (1.5%) around a break draft of 1.6–1.7. The minimum variability of drafting force well corresponds with lower irregularity of sliver at certain break draft ratios. This indicates that a stable drafting force promises better fiber distribution along the sliver length. The variability of drafting force and sliver irregularity also increased as the back gauge increased from 43 to 51 mm. Furthermore, the impact of short fiber content on the drafting force was investigated at three back gauges. The increase in short fiber content gives higher magnitude of drafting force. Drafting force was also compared with the number of neps and change in fiber length in sliver for each break draft. Better nep opening and improved fiber lengths were also found around (1.6–1.7) break draft and follow the same trend of variability of drafting force as the break draft changed.