USTER H Index Hairiness Measurement

USTER H index (hairiness index) is measured simultaneously during evenness testing on the USTER Tester 6 by a dedicated optical sensor module (700 nm laser diode, 4-quadrant photodetector array surrounding yarn path at 1 mm reference distance) detecting scattered light from protruding fibres as yarn passes at 400 m/min. H = total protruding fibre length per cm of yarn (dimensionless but equivalent to total mm of protruding fibres per cm — H = 6.0 means 60 mm of protruding fibre length per cm of yarn path). H value generation: each individual protruding fibre contributes proportionally to H based on its length beyond 1 mm reference distance — a 3 mm fibre contributes 3× more to H than a 1 mm fibre. Hair variation index sH% (CV% of hairiness, 1 cm measuring intervals): sH < 1.0% for standard ring yarn, sH > 2.5% indicates spindle-to-spindle hairiness variation causing barré in knitted fabric. Compact spinning effect on H: Rieter Com4 attachment reduces H from 5.8 to 3.2 (−45%) for Ne 30 cotton versus standard ring by aerodynamic condensation of spinning triangle from 3–5 mm to <1 mm — fewer loose fibre ends incorporated into yarn body. Rotor yarn H value: 6.0–8.5 for Ne 20 rotor cotton (higher than ring due to open-end twist geometry wrapping loose fibres as wrapper fibres on surface). Air-jet/vortex yarn (Murata MVS): H = 1.5–3.0 for Ne 30 (lower than ring spinning due to fibre wrapping mechanism creating smooth surface — ideal for anti-pilling performance in knitwear). Correlation between H and fabric pilling (Martindale ISO 12945-2, 2,000 cycles): H 3.0 → pilling grade 4.5/5; H 5.8 → grade 3.5/5; H 8.0 → grade 2.5/5 — each unit of H increase corresponds to approximately 0.3 grade reduction in pilling resistance.