Yarn Manufacture and Yarn Properties
What the exam tests
You should be able to sequence the spinning process, explain what each machine does to the fibre assembly, and relate yarn count, twist and blending to strength, evenness and handle.
Cotton spinning sequence
Blow room (opening, cleaning, lap or chute) → carding (individualising fibres, removing trash, forming sliver) → drawing (doubling and drafting for parallelisation and evenness) → roving (further drafting, small twist) → ring spinning (final draft, twist insertion, winding). For fine counts, a comber is inserted between card and draw frame; combed yarn is smoother, stronger and more expensive because short fibres and neps are removed.
Wool and filament routes
Worsted processing uses carding, combing, gilling, drawing, roving and spinning to give a smooth, compact yarn. Woollen processing cards and spins on the mule for a soft, bulky yarn. Filament yarns are extruded, drawn and textured - false-twist texturing adds crimp, bulk and stretch.
Count and twist
Tex is the mass in grams of 1000 m; English cotton count (Ne) is the number of 840-yard hanks per pound, so a higher Ne means a finer yarn. Twist per inch (TPI) raises strength up to an optimum; beyond it, strength falls and the yarn becomes lively and snarling. Ply yarns are more even and stronger than singles.
Worked example
A yarn is labelled 40s Ne. Using tex = 590.5 ÷ Ne, tex = 590.5 ÷ 40 ≈ 14.8 tex. Check: one hank is 840 yd ≈ 768 m; 40 hanks = 30,720 m per pound (453.6 g), so 453.6 ÷ 30.72 km ≈ 14.8 g/km. A 20s yarn would be 29.5 tex - twice as coarse.
Traps that cost marks
Do not confuse carded with combed yarn. Higher twist is not always stronger. Roving is not the final yarn. In count conversion, remember that a higher Ne means finer, while a higher tex means coarser.