Thesis Details

Thesis Title: An Investigation of On-line Quality Monitoring Systems in Predicting the Quality of Textured Yarns and Comparison with the Standard Knit-Dye Quality Control Procedure
Thesis Author: Kimberly Carlan
Abstract: The quality of textured yarns is currently measured by the knit-dye quality control procedure. In this procedure, the last 100 meters of yarn or less on a package are knitted into a sock, dyed, and then graded. Packages are passed or rejected by comparing the sock with a control package. Since the sampling is limited, a large percentage of production is untested. Intermittent faults and other faults that occur throughout production can be missed. Also, since testing occurs after production, several thousand yards of off-standard yarn could be produced before a problem is identified and corrective action taken. i On-line tension and bulk monitoring systems give textured yarn manufacturers the capability to monitor 100 percent of production and perform timely corrective action. However to replace the knit-sock dye procedure, textured yarn manufacturers must understand how textured yarn quality compares with the on-line measurements of yarn bulk and thread line tension. Since the quality of textured yarns is currently evaluated using knit-sock dye tests, on-line measurements of bulk and tension were compared with the dye indicator value obtained from this test. Since shifts in primary heater temperatures can cause variation in dye depth that may not be detected by the tension or bulk values, the dye depth indicator value was also compared with the near-infrared heat history value of the textured yarn. While average measurement values of thread line tension and yarn bulk did not compare with the results of the knit-sock dye test, surges in tension and yarn bulk values did identify yarn defects. Deviations in dye depth that were not detected by the on-line systems could have been related to heat history differences, raw yarn properties or other process deficiencies. Neither the on-line tension nor bulk systems could detect a lOOoe change in the primary heater second zone temperature. Near-infrared measurements of heat history did detect significant changes in primary heater temperatures. The near-infrared method identified an approximate 25°e change in yarn temperature that was not reflected in the thread line tension and yarn bulk measurements.