Abstract: Drafting is one of the four major mechanical effects in the spinning process, and the quality of the drafting effect directly affects yarn quality. During the roller drafting process, the fibers in the sliver slip with each other at variable speed points, so the distribution if fiber variable speed points has the most significant influence on the yarn quality. So far, plenty of literature has analyzed the qualitative effects of fiber types, drafting methods and drafting multiple on variable speed points, but these studies are all under ideal assumptions, and they have not yet given quantitative test of variable speed  points distribution. Furthermore, the unevenness of the yarn after drafting is not only influenced by the differences in variable speedpoints but also by the drafting multiple. Therefore, the unevenness of the yarn after drafting does not directly reflect the stability of fiber movement.
  Therefore, after analyzing the mechanism of roller drafting, this study presented a new method to test the distribution of variable speed points in the roller drafting zone. The slivers were cut at equal lengths and weighed, and then based on the weight change of the slivers in the drafting zone, the distribution of the variable speed points was characterized. On the basis of the data obtained from the test, the theoretical formulae characterizing the stability, concentration, and forward movement of the fiber velocity variation point distributions in the drafting zone were derived with the assistance of data processing methods. Under the condition of keeping the process parameters constant, experiments were conducted by using combed and carded slivers as raw materials for blending. Validation analysis was performed on the provided formulas, revealing that the distribution of variable speed points in combed slivers is more concentrated, stable, and forward-moving. Consequently, the quality of the resulting yarn is superior. The more dispersed the variable speed points are in carded slivers, particularly those away from the front nip, the higher their range coefficient will be, leading to greater unevenness in the sliver. Therefore, to improve the evenness of the sliver, it is essential to effectively control fiber movement and set reasonable process parameters to make the distribution of variable speed points more concentrated, stable, and forward-moving.
The present study characterizes the distribution of variable speed points in the drafting zone using the distribution of fiber mass changes. It analyzes the regions where fiber speed change points are concentrated within the drafting zone, and compares the strip performance to explore the relationship between the distribution of fiber speed change points and strip quality. The aim is to investigate the laws of fiber speed variations within the drafting zone. It provides a quantitative approach to studying the distribution of fiber speed change points in roller drafting. The study facilitates the selection of optimal drafting components and the development of optimal drafting processes. This improves sliver performance and yarn quality. On a practical level, the rationality of the drafting process can be judged, and the quality of the slivers in the drawing process can be analyzed and predicted. On a practical level, it is possible to judge the rationality of the drafting process, analyze and predict the quality of the slivers in the drawing process. This has significant economic implications for optimizing drafting process settings and improving drafting efficiency.

Key words: drawing, variable change point, draft zone, equal length cutting weighing method, mass distribution

摘要： 为探究并条机牵伸区内纤维变速点分布的特点，以纺制定重为15.35 g/5m的普梳条和15.03 g/5m的精梳条为例，采用FA320A型高速并条机进行实验，对罗拉牵伸区中的须条进行定长的切断称重得到纤维质量分布，以其纤维质量变化率分布表征变速点分布，并在此基础上借助数据处理的方法分别给出定量表征牵伸区内纤维变速点分布稳定性、集中性、前移性的理论计算公式，并通过并条实验对所给出的公式进行了验证分析。结果表明：该理论计算公式可以判断出变速点分布的位置及状态；在此实验中，精梳条中的纤维在距前罗拉钳口线5~15 mm处变速相对集中且前移、稳定性好；普梳条中的纤维变速点分布较为分散，且远离前罗拉钳口线。该研究为变速点分布理论的发展提供了参考，有助于预测成条质量、提高并条效率。

关键词: 并条, 变速点, 牵伸区, 等长切断称重法, 质量分布