Yarn Manufacture and Spinning
Yarn Manufacture and Spinning covers the conversion of fibre mass into continuous yarn, from opening to final winding. The exam tests process sequence, drafting, twist insertion, count systems and production calculations.
Core concepts
- Short-staple sequence: blowroom, carding, drawing, combing for fine yarns, roving, ring spinning. Combing removes short fibre and neps.
- Drafting attenuates sliver or roving; roller settings and fibre length control fibre control.
- Ring spinning inserts twist via traveler and spindle; compact spinning reduces the spinning triangle and hairiness.
- Rotor spinning is faster but usually coarser and has a different fibre arrangement.
- Count systems: tex is direct; Ne is indirect. Twist multiplier relates TPI to count.
Worked example
For a 30 Ne cotton yarn with twist multiplier 4.0, TPI = TM × sqrt(Ne) = 4.0 × sqrt(30) = 21.9 turns/inch. If spindle speed is 15,000 rpm and TPI is 21.9, delivery speed = 15,000/21.9 = 685 in/min, about 17.4 m/min. This assumes steady state and no twist loss.
Traps
- Using TPI = TM × Ne instead of sqrt(Ne).
- Mixing English and metric counts in one calculation.
- Ignoring twist direction and its effect on fabric appearance.
- Calculating production without efficiency, waste or end-break losses.