关键词: 变速点分布, 半精梳条, 牵伸区, 等长切断称重法, 成条质量

Abstract:

Objective Drafting in the yarnmaking process involves multiple technical steps, and the quality of the sliver is the main indicator for evaluating the drafting effect. In practical drafting processes, there exists a speed differential between the front delivery nip and the rear feed nip, resulting in inter-fiber slippage and the attenuation of the sliver from thick to thin. Due to the inconsistent variable speed positions of fibers in the stretching zone, any two fibers would undergo displacement deviation after variable speed, resulting in uneven stretching, and this is the main reason for quality deterioration of the slivers. Therefore, the distribution of fiber accelerating-point has been identified to have significant impact on the quality of the sliver.

Method This study investigated the relationship between the distribution of fiber accelerating-point in the drafting zone of the drawing machine and the sliver quality of semi-combed cotton slivers with different blending ratios, using combed and carded slivers as raw materials. Five types of semi-combed cotton slivers were spun separately using the FA320A high-speed drawing frame under the same process parameters, with combed/carded sliver ratios being 1/5, 2/4, 3/3, 4/2, and 5/1. Then, the obtained 5 types of semi-combed cotton slivers, combed cotton slivers, and carded cotton slivers were each subjected to cutting and weighing. Subsequently, based on the distribution of fiber mass change rates, an analysis was conducted on the distribution of main drafting zone fiber accelerating-point, including the concentration, stability, and fronted movement of the fibers accelerated-point.

Results The experimental results sjowed that as the proportion of combed slivers increased, the distribution of fibers at the accelerating-point became more concentrated towards the front roller nip line. A more concentrated and forward distribution of fibers at the accelerating-point indicates better control over the coefficient of variation. This implies that the stability control of the severed and weighed slivers at the same nip line is better over different time intervals. Consequently, the mean deviation and coefficient of variation of the sliver after drafting were smaller. When the proportion of combed slivers reached a certain level, the differences in the concentration and forward distribution at accelerating points became negligible, and the differences in the sliver after drafting appeared minimal, resulting in overall superior quality. It was evident that the more reasonable the setting of blending process parameters, the better the stability control of the logarithmic variance of fibers accelerating-point distribution, all of which are smaller than the critical value. This indicates that external factors have minimal interference on the sliver quality of these seven groups. On the contrary, the higher the proportion of carded slivers, the more unstable the fibers accelerated-point, the more dispersed the fibers at the accelerating-point were away from the front jaws, the wider the range of speed change position at the fiber head end, and the greater the displacement deviation, resulting in a larger average difference and coefficient of variation. It was also found that the more uneven the yarn, the worse the fiber elongation, parallelism, and separation degree in the yarn, and the easier it is to produce coarse and fine knots. Disrupted fibers during the stretching process would cause deterioration of the yarn quality.

Conclusion In actual spinning processes, it is necessary to allocate blend ratios reasonably and set appropriate process parameters to enhance the uniformity of sliver weight. This optimization worked to improve the concentration, forward distribution, and stability of fibers accelerated-point, thereby enhancing sliver quality. This is of great significance for spinning enterprises to achieve effective control of fibers in the drafting area, predict the quality of slivers, and optimize the process parameters in drawing production.

Key words: accelerated point distribution, semi-combed sliver, drafting zone, equal length cutting weighing method, sliver quality