Tuesday, 16 December 2008

Impact of rotor machine variables on yarn quality



Impact of Rotor machine variables on Yarn Quality

On increasing rotor speed

1. Centrifugal force (g.tex) increases

= (w^2 x 0.981)/20000, w= pi x D x N
where D= Rotor dia in meters
N= rotor rev/second

so there is better fiber consolidation and better strength

2. Combing roll efficiency will reduce , fibres get deposited in rotor groove in bunches and not in single file and so strength reduces.

3. Hooks will get less time to straighten

4. Number of wrapper fibers will increase

5. Also yarn elongation decreases at higher rotor speed

On increasing rotor diameter

a. % wrapper fibres = l x 100/ pi x D
where l= effective length of fibres used
so as D increases, % reduces so strength increases

b. No of doublings inside the rotor
pi x D x TPI

so evenness and imperfection reduces, strength increases

c. Reduction in spinning in coeficient at higher rotor diameter. This leads to weaker yarn.

d. Higher power consumption

PC ( Watts) = K n^2.5 D^3.8

n--> rotor speed ( rev/min)
D--> rotor dia in mm
k--> a constant

e. Yarn elongation decreases at higher rotor diameter

On Increasing Draft

Increasing draft will increase fibers breakage due to increase in the value of carrying factor (ie. no of points per fibre) optimum should be 120-150

Combing roll speed should be around 6000-8000 rpm

Design of Doffer tube

Grooved tube permits yarn to be produced at lower twist factor but poor fiber orientation and high short term variability.

Affeect on Twist

Higher twist: Elongation increase, and abrasion decreases

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