Test of yarn twist
There are two methods for testing the twist of spinning yarn, namely the direct de-twisting method and the tension method. The tension method is also called the twist-removing (retracting) twist-adding method. There are currently three types of twist testers (Figure 2-14): plane constant tension type [Figure 2-14(a)], straight-standing type [Figure 2-14(b)], and manual type [Figure 2-14(c) )] (for roving). (1) Direct de-twisting method: Clamp the sample under a certain tension in the left and right yarn clamps of the spinning yarn twist meter. Let one of the yarn clamps rotate in the opposite direction to the original twist direction of the spinning yarn. When the twist on the spinning yarn is completely reversed, the yarn clamp stops rotating, and the reading at this time (or printed by the printer) is the number of twists on the spinning yarn. This method is mostly used to measure filament yarns, strands or rovings with little twist. (2) Tension method: The sample is clamped in the left and right yarn clamps under a certain tension and is first untwisted. At this time, the spinning yarn is untwisted and elongated. After the twist of the spinning yarn is completely untwisted, it continues to rotate and the twist will be added. And shorten until the length of the spun yarn is twisted to the same length as the original sample, the yarn clamp stops rotating, and the reading at this time is twice the number of twists of the original spun yarn. This method is mostly used to measure the twist of short fiber single yarn.
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