Thesis Details

Thesis Title: The effect of sliver drafting force and drafting force variability, as measured by the modified ITT Draftometer, on ring and air-jet yarn quality parameters
Thesis Author: Earle Wolynes
Abstract: In the manufacture of short staple yarns, many factors affect the quality of the final product. These factors range from fiber characteristics to machine settings and even operator practices. To achieve quality yarn manufacturing one must control all factors which cause deteriorations in raw material, sliver, and resultant yarn quality. One such factor which has been investigated since the late 1940's is drafting force. Drafting force is defined as the force necessary to move fibers past each other in a drafting zone. Like yarn quality itself, many factors such as fiber characteristics and machine settings affect drafting force. Longer more crimped fibers, higher fiber entanglement, and closer roll spacings all lead to higher mean drafting force. Lower levels of drafting force can be caused by wider roll settings, higher fiber alignment, higher drafts, and lower roving twist. Drafting force and drafting force variability exist to different degrees in all types of fiber assemblies. Many research articles have been written relating fiber characteristics and drafting force; however, few have gone the additional step to determine proper machine settings as they relate to drafting force and drafting force variability. Research associated with drafting force and drafting force variability in roving was completed by Feil in the early 1980's. This research showed that drafting force and drafting force variation affect the quality of ring spun yarn. Feil related drafting force variation to actual spinning frame break draft settings. Using the ITT Draftometer, Feil determined that certain spinning frame break draft settings yielded a higher degree of drafting force variability. This high force variability area became known as the critical draft region. When spinning break drafts are set in the critical draft region fibers do not draft uniformly, but instead, draft in the sliding and stopping motions, which in turn negatively affects ring yarn quality. It was the objectives of this research to determine if a critical draft region exists in finisher drawn sliver, and if it does, what effect does it have on yarn quality. In addition, the effects of finisher drawn sliver drafting force and force variability on ring and air-jet yarn quality was investigated. This research was completed for four fiber blends, three of which were ring spun, and one spun on an air-jet spinning machine. All drafting force and drafting force variability data were obtained using the ITT Draftometer which had been equipped with a more sensitive measuring head capable of measuring the small interfiber forces associated with finisher drawn sliver. Multiple correlation analysis on the data generated concluded that critical draft as measured by the modified ITT Draftometer does not exist in finisher drawn sliver. However, finisher drawn sliver drafting force and drafting force variability either seperatly or in conjuntion with break draft did significantly correlate with both ring and air-jet yarn quality. These correlations which show that the modified ITT Draftometer can be used to predict both ring and air-jet yarn quality are as follows: 1. Increases in the product or interaction of roving frame break draft and mean sliver drafting force improves yarn quality. As the interaction increases improvments are witnessed such as lower ring yarn Uster CV, higher adjusted single-end strength and break factor, better yarn appearance, and lower levels of Uster thins, Uster thicks, and Classimat minors. 2. Increases in drafting force variability of the finisher drawn sliver lower the ring yarn elongation and the degree of Uster neps. 3. Increases in the product of break draft and mean drafting force increase the Uster CV, elongation variability, and amount of Classimat thicks in air-jet yarns. 4. Increases in the product of break draft and drafting force variability increases the Uster CV variability, lowers the adjusted break factor and single-end strength. Higher single-end variability, lower Uster thicks, and higher Classimat minors and thicks are noticed as increases in air-jet spinning break draft and sliver drafting force variability.