Abstract: Effect of carding machine heel-toe difference on yarn hairiness number is studied. The hairiness of yarns processed by 24 plans under four-grade flat heel-toe difference, two-grade cylinder speed and three-grade carding output was tested by YG172 yarn hairiness tester. The test results were analyzed by SPSS software. The results show that heel-toe difference has notable influence on yarn hairiness index. When cylinder speed is 394r/min, the yarn hairiness is the least under 0.42mm heel-toe difference; while cylinder speed is 296r/min，the yarn hairiness is the least under 0.56mm heel-toe difference. In all test plans, the heel-toe difference of 0.56mm and 0.42mm are beneficial to hairiness reduction as a whole；the yarn hairiness is the most under 0.14mm heel-toe difference, which shows that too small heel-toe difference is not conducive to hairiness reduction.

Key words: carding machine, heel-toe difference, cylinder speed, doffer speed, yarn hairiness