ABSTRACT

The presence of neps in a yarn is not a positive phenomenon from the point of view of yarn quality. The presence of a nep not only decreases the yarn and fabric appearance, but also makes the further stages of processing, (process of warp preparation, weaving and knitting) difficult.

Assuming as follows:

• each cotton yarn linear density corresponds to the critical nep size, i.e., such size, beyond which nep or trash particles in the roving are identified and registered by the Uster tester as yarn neps,
• percentage distribution of nep size in the roving is similar for all rovings produced by the same spinning system (carded and combed),

we propose a coefficient of the nep and trash visibility η. This parameter describes the nep and trash number in the roving, which are transferred into the ring-spun yarn, and they are identified by the Uster Tester as yarn faults at device settings of sensitivity +200%.

Based on the laboratory measurements of a large amount of cotton rovings producing yarns, we determined the coefficient of the nep and trash visibility η for a different assortment of neps and trashes. This coefficient allows the assessment of the predicted nep number per 1000 m of ring – spun yarn according to the Uster tester.