PERFORMANCE EVALUATION OF A CIRCULAR WEFT KNITTING MACHINE THROUGH OBSERVATION OF YARN INPUT TENSION: A CASE STUDY

Abstract

This paper presents a noble approach to assess the performance of a modern knitting machine through monitoring of running yarn tension during operational hours. An industrial circular weft knitting machine having positive storage feed system was observed, as a case study, in this research for its performance evaluation. A total of 16 different production runs- each for a machine running period of 30 seconds [equivalent to the time required for more than 05 revolutions of the needle bed or machine at 10.5 rev. /min.] were analyzed. Highest tension-peak value for each second was identified through MLT Wesco Yarn Tension and Rate Meter and associated PC software. Run charts were built-up with these selected tension values by a statistical software, i.e. Minitab and the p-values were checked to identify special cause variations. It was found that most of the production runs showed no non-random pattern in the tension values based on an alpha value (significance level) of 0.05, representing absence of special cause variations and thus disclosing quite satisfactory machine performance. However, the production run with non-random pattern was investigated through cause-effect diagram. The presence of astronomical data point was also evaluated. The findings here also indicated no direct machine-related cause regarding such variation or pattern in yarn input tension.

Keywords

• Knitting
• Yarn Input Tension (YIT)
• Run Chart
• Special Cause Variation
• p-Value