Yarn Evenness and Imperfections

Yarn evenness describes how uniform a yarn's mass is along its length, usually measured as U% or CV%, together with counts of imperfections such as thin places, thick places and neps per kilometre.

Evenness testers pass yarn through a capacitive sensor that responds to the mass of material in the measuring zone, producing a continuous signal from which mass variation is calculated as U% or CV%. The same tests count imperfections above set sensitivity levels, namely thin places, thick places and neps, and a spectrogram reveals periodic faults caused by eccentric or damaged drafting rollers.

Uneven yarn produces visible streaks, cloudiness and barre in fabrics and contributes to end breaks in weaving and knitting, so evenness is a core quality parameter for spinning mills and their customers. Uster Statistics are widely used as a reference for comparing a mill's yarn quality with industry levels.

On winding machines, electronic yarn clearers monitor the running yarn and cut out objectionable faults, including thick and thin places and foreign fibres, after which the ends are spliced. Clearer settings balance fault removal against the number of cuts and splices. Results depend on test speed, settings and conditioning, so test parameters must be stated when results are compared.

Key points

Mass variation along the yarn, reported as U% or CV%
Imperfections are thin places, thick places and neps per kilometre
Spectrograms reveal periodic faults from drafting rollers
Electronic clearers cut out objectionable faults during winding

Where AiVibe comes in

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Related terms

Terms that refer to Yarn Evenness and Imperfections

Rotor Spinning (Open-End Spinning)Textile & Automotive Manufacturing