The cause and the feature of draft-cut wave are described in this artcle. The draft-cut process can be divided into three stages of process—stretching, breaking and drafting. The drafting process is affected by the breaking position, and is one of the major causes of the draft-cut wave. The method of drawing the draft-cut wave from a staple diagram of sliver in some typical cases is shown.

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In the drafting of sliver, it is necessary to know staple length which represents the length of all fibers in sliver, in order to fix a suitable roller setting. Several methods have been devised by experts to determine such staple length. The authors have developed a new method. It is based on a “represntative staple length” theory derived from the drafting theory. Representative staple length as gained by the authors has been used to analyze staple diagram. Examples of evaluation of the staple diagram of several species of raw cotton by this method are given.

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This article considers how to regulate the draft ratio to make drafted sliver most uniform by means of an automatic control device such as the Autoleveller made by Prince-Smith & Stells Ltd. After some theoretical studies, the authors have arrived at the following methods:
(1) Measure the thickness variation of ingoing sliver at the back nip point or at some other proper point before it passes the back nip point.
(2) If it is observed that a portion of ingoing sliver is thicker or thinner by α% than the mean thickness, then increase or decrease the draft ratio by α% when this thick or thin portion reaches the point s+l/2(1+_??_) distant from the front nip point toward the back nip point. As to s, _??_ and _??_see the Summary and Conclusions.

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The authors have perfected a U% integrator for analyzing yarn evenness and explain herein its basic principle. By way of comparison, we also set forth the principle of a yarn evenness evaluation method which uses an air micrometer. Examples of the working of the new device are given.

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