Drawing Frame and Autoleveller
topic
Drawing frames improve sliver uniformity and fibre parallelisation by drafting 6–8 slivers simultaneously through 3-over-3 or 4-over-4 roller drafting zones (total draft 6–8×, break draft 1.3–1.5×, main draft 4.0–6.0×) at delivery speeds of 400–1,000 m/min, with online autoleveller correction maintaining delivered sliver CV% below 1.0%. Two passage drawing is standard: breaker draw frame (1st passage, 6–8 card slivers doubled, delivery 5–6 ktex) then finisher draw frame with autoleveller (2nd passage, 6–8 breaker slivers doubled, delivery 5–6 ktex, CV% < 1.0%). Autoleveller systems: open-loop (measuring sliver at input, correcting draft after feed roll delay — correction delay 0.3–0.5 m) or closed-loop (measuring output sliver, immediate feedback correction — preferred for medium-wave variation 20–100 mm) achieving ±0.5% weight uniformity. Modern draw frames (Rieter RSB D 45, Trützschler TD 10, delivery speed 1,000 m/min) incorporate inlet scanning (tongue-and-groove roller sensor measuring 1 mm wave variation), fibre length profiling, and can stop-motion for sliver run-out. Sliver can filling: automatic can changer deposits sliver in 400–600 mm diameter cans at 1,000–1,500 m capacity per can for downstream roving frame or rotor spinning. Fibre parallelisation improvement: fibre orientation angle reduces from 20–30° (card sliver) to 5–10° (2nd draw frame sliver), directly improving yarn tenacity by 8–15%.
Role
Drawing frames with autolevellers are the precision quality control checkpoint in the staple fibre spinning preparation route, with sliver CV% delivered from the finisher draw frame being the single most predictive parameter for ring yarn evenness (Uster CV%), thick places, and thin places that determine fabric appearance quality and consumer acceptance.