Thesis Details


Thesis Title: The economic optimization of waste removal at opening, picking, and carding
Thesis Author: Barry Knight
Abstract: In the manufacture of carded cotton yarn, a certain amount of waste must be removed from the raw stock in order for the finished yarn to meet specifications in Appearance Index, Uster Imperfection Count, Uster Evenness, %CV, single end strength, elongation, adjusted break factor, and others, depending on the end product. Waste, which includes trash, both cellulosic and noncellulosic, and non-spinnable fiber is deliberately removed at the initial cleaning processes of opening, picking, and carding. Also, some spinnable fiber is sacrificed as a byproduct of the various cleaning process.e.s. Although various mlll standards for waste removal have been in use, there have been no proven criteria for waste removal levels at the various cleaning processes and their effects on resultant yarn quality and the economics of waste removal. Therefore, it was decided to investigate the effects of the combinations of six levels of waste removal at opening and picking with five levels of flat speed, and hence levels of flat strip waste, at carding with respect to the resultant effects on yarn quality and economics. Using Strict Low Midling, inch and one-sixteenth cotton, yarn was produced from each of the thirty waste removal combinations. The yarn was then tested for adjusted break factor, single end strength, single end elongation, Uster Evenness, %CV, Uster Imperfection Count, and Appearance Index. Several conclusions were drawn from the investigation. Increasing the per cent waste at opening and picking' had a highly negative effect on the yarn qualities of adjusted break factor, single end strength, and single end elongation because of the fiber damage associated with the amount of processing necessary to achieve the higher levels of waste removal. No strong relationships were found to exist between flat speed, per cent flat strip waste, per cent total card waste, or per cent total waste, opening through carding, and any of the yarn qualities tested. The data suggested that the opening and picking conditions used damaged fibers, the damage becoming apparent at carding. For a particular total waste level, the waste should be removed at the card rather than at opening and picking, if the pre-carding equipment is the same as that used in this thesis. The lowest per cent total waste, opening through picking, used in the thesis, 2.34 per cent, resulted in yarn qualities which were generally equal to or better than the yarn qualities resulting from the higher per cent total waste levels. Therefore, it was suggested that mill standards for waste removal might be lowered, resulting in a significant reduction for the cost of waste removal.