2012 Volume 68 Issue 1 Pages 6-10
The twist of yarn is one of its important properties. The amount of twist inserted in a yarn is a factor on which are dependent, not only tensile strength, but also a number of properties which contribute to yarn quality. The common method for testing final twist, an attribute of double-ply yarn generally used with flat knitting machines, consists of untwisting the yarn. We propose a method for extracting an outer profile from an image of yarn which is scanned by running the yarn in front of a CCD camera. The number of peaks in the outer profile is related to the number of final twists in the yarn. The number of final twists can be estimated by calculating their frequency in the outer profile using FFT. This paper shows the results of this new method, compared with those of the ordinary method of untwisting yarn.
