26Wrap PRINCIPLE APPLICATION AREAS USESS
- 1. 1 Tension F Tension F Pressure Tension in length direction causes pressure in radial direction Pressure binds fibres together, preventing fibre slippage Effects of Twist Yarn formation process in which a twistless staple fibre strand is wrapped by a binder yarn W Klein, "New Spinning Systems", T.I., 1993. Section 1.5 Gemmeill & Dunsmore test rig 1974, prototype 1975 ITMA Invented by George Mitov of Institute of Clothing and Textiles (DSO "Textil“) in Bulgaria Wrap Spinning Commercial machine 1976 Hollow Spindle (Wrap) Spinning Fibre strand with no wrapping & no strength
- 2. 2 False Twist Principle S twist Z twist Twister Static Condition No. of S twist = No. of Z twist A B Zero net twist between A & B False Twist Principle Dynamic Condition A B Twister V (m/min) n (rpm) C Zero net twist after twister Twist before twister = n/v False Twister 320 t/m 400 t/m 560 t/m With false twist Without false twist Main Process Parameters Wrapping density (compare with twist) Wrapping tension (compare with twist) Spindle speed False twist Binder linear density (20-110 dtex; 1-15% of total yarn) Binder type Filaments (synthetic esp. nylon, glass, carbon….) Metallic Staple/fancy yarn Soluble (e.g. polyvinyl alcohol) Binder (e.g. binder tex, package type)
- 3. 3 Main Process Parameters Spindle speed (to 35,000 rpm) Production speed (to 200 m/min) Core fibre (esp. long staple) End-use Yarn linear density Domestic textiles (e.g. blankets, wall covering) Carpets (untwisted fibre softer feel+denser cover) Fancy yarns Specialist fibre can be used Hand knitting Advantages Very low doffing & piecing frequency High production speed Low ends down rate (30% of ring) Shorter process Low production cost Compared with ring spun yarn Better absorbency Lower hairiness/less lint shedding Less untwisting tendency Higher strength possible (up to +100%, parallel fibre) Thinner yarns possible Multi-component yarn in single process Greater volume (+20%) when not under tension Wide range of fibres can be used Disadvantages Limited to multi-component yarn Poorer yarn handle (stiff, rough) Binder can be expensive Separate winding required for binder
- 4. 4 Balanced yarn No need for heat setting/steaming No spirality in knitted goods Two stage wrapping / wrapping & ring twisting Wrap-spun Fancy Yarns Easier change of yarn type Mixing roving/slivers with fibres of different dyeing properties/staple length Random effects achieved without sophisticated patterning devices Yarn appearance can be seen immediately without being affected by the reverse binding as in ring twisting Single process Require min. 3 components (core, effect, binder) Untwisted core/effects (bulk, handle, performance)
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