Calculating ASTM D5430 Demerit Scores for Complex Linen Twill Lots
ASTM D5430 demerit scores for wide linen twills normalize defect counts per 100 square yards or metres to enforce commercial lot acceptance thresholds.
Flax Yarn Slubs
Thickness Anomaly
Thick places in spun linen yarn represent localized increases in linear density caused by unattenuated fiber bundles or irregular drafting. Persistent flax yarn slubs appear as abrupt, short thick sections where fiber mass exceeds standard yarn diameter by fifty percent or more over short distances. Quality control inspectors grade yarn lots using electronic yarn clearers that count and categorize these defects during high-speed winding.
Sales specifications declare maximum allowable slub frequencies per hundred thousand meters of yarn to establish commercial acceptability.
Defect Detection
Drafting roller accumulation or improper roller pressure triggers local bunching during flyer spinning or wet spinning operations. Capacitance or optical sensors on automatic winding machines scan the running threadline to detect flax yarn slubs, comparing size and length against set clearing curves. When an anomaly exceeds configured thresholds, the winding head cuts the yarn, clears the thick section, and joins the ends with a mechanical splice.
Laboratory yarn evaluation logs record short slubs separately from long thick places to pinpoint whether carding deficiency or spinning frame drafting error produced the defect.
Severity Boundary
Controlled slub count specifications apply to smooth, uniform yarn grades intended for plain apparel or table linens. Flax yarn slubs are intentionally preserved or adjusted when producing specialty slub yarns designed for textured decorative fabrics.