To provide a method etc. capable of promptly and accurately detecting dirt on heads of photoelectric type yarn clearers.
In this method for detecting dirt on the detection heads of the plurality of yarn clearers mounted to a machine frame system comprising a plurality of spindles to monitor yarn quality etc. in each of the spindles, whether change of yarn thickness data () and/or yarn uniformity ratio data (CV%) obtained based on yarn unevenness signals output from the yarn clearers of the specific spindles is caused by change of the characteristics of the monitored yarn itself or by dirt on the detection heads is determined from the relationship between yarn thickness data () and/or yarn uniformity ratio data (CV%) obtained based on yarn unevenness signals output from the yarn clearers of the other spindles.
SAMOTO YOSHIHIKO
NOMA EIJI
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