ROTOR SPINNING TECHNOLOGY

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ROTOR SPINNING TECHNOLOGY

1. Feed sliver                                   

2. Feed roller

3. Feed trough

5. Opening roller

8. Feed tube

9. Rotor

10. Free end of yarn

16. Naval

17. Withdrawl rollers

18. Rotor groove 

 

Features of rotor spinning

•          It can process waste materials like short fibres, comber noil – excellent recycling machine

•          Per rotor production is 4 – 10 times higher than ring spindle

•          Card D/F sliver is used as feed material – many processes removed

•          Bigger package like cheese – reduced doffing cost

•          Lower fibre migration in rotor – uniform distribution of component fibres in blends

•          Less irregularity

•          Less hairiness of yarn

•          Lower strength as compared to equivalent ring yarn 

In order to achive ideal fibre flux i.e. Unity {fibre flux =number of fibres in cross section},in the transport tube , the air speed in the tube would have to be as high as 75m/s for fine yarns & 600 m/s for coarse yarns. {Generally flux = 7-8}.

Some straightening of fibres occur as they enter the rotor, since the surface speed of the rotor is greater than the air-speed. 

•         Centrifugal force flings the fibres outwards & presses them onto the collecting surface of the rotor ,where a ring consisting of many layers of fibres forms.

•          To start spinning ,an existing seed yarn is introduced through the exit tube . since the rotor & the air contained in it are rotating , the yarn tail is also caused to rotate.

•          Centrifugal force throws it against the inner peripheral surface of the rotor ,where it makes contact with the ring of fibres. As soon as this occurs, the seed yarn is withdrawn , and yarn production begins.

•          Each revolution of the yarn arm puts a turn of twist into the yarn in the exit tube, &, since there is little to stop it , some of this twist leaks back along the yarn arm to the rotor surface, which thus causes the tip of the seed yarn to become entangled with the ring of fibres , which can then be progressively peeled off the surface of the rotor to form a yarn.

•          The yarn produced is simply wound onto a large package, usually a cheese. 

 

1.           Opening roller
3.              Trash Removal
5.                 Edberg Venturi 

Fibre Properties Required for Rotor Spinning

Fibre strength                                 Fibre fineness

Fibre length/length uniformity  Fibre cleanliness

Fibre Strength –     Higher the better

                                Linear relation between fibre & yarn strength

Fibre Fineness –   more no. of fibres are reqd in X-section than

                               ring spun yarns due to poor orientation

Finer fibres :         Higher yarn strength

                               higher fine yarn count limit

                               less twist reqd for optimum strength

                               better handle due to reduced flexural rigidity

                              But too fine fibres may get damaged in opg roller .

Fibre length / length uniformity:

Rotor can produce better qlty yarn from shorter fibres

Shorter the fibres : Reduced wrapper fibres

                          reduced hooked and looped fibres – effective fibres length

                          reduction in the twist loss in yarn and tenacity of fibres

But for finer counts, length need to be higher

Fibre length should not be more than diameter of rotor

Fibre cleanliness: Very Very Important

Presence of trash, dirt & dust is very problematic  

Ø  disturbances in the yarn formation process – end breaks

Ø ‚Moire‘ diamond patterning effect due to periodic change in  yarn apppearence

Ø  Effect of microdust.

MICRODUST

Fine fragment of fibres and dust of size  1- 50 micrometer

 difficult to remove due to their strong bonding with fibres through ----- electrostatic charges
Also generated in B/R and C/D
50 – 80 % of MD are cellulosic components, they escape all clg.        points and accumulate in rotor groove – leading to poor quality     yarns and end breaks
 MD also reduces rotor operating life So, MD must be removed
Other Foreign Matters

Foreign fibres, Mineral dusts, Honey dew, Spin finish.

RAW MATERIAL REQUIREMENTS:

Fineness should be HIGHER

Strength should be  HIGHER

Maturity should be BETTER

Short fibre % should be LOWER

Trash content should be LOWER

Theory of Yarn Formation:

  The Fiber Flow into The Rotor

 Formation of Coherent Fiber Strand

Back Doubling :

Formation of the yarn

Twist in yarn

Wrapping fibres

Binding fibres

Fibre integration in the yarn

Structure of rotor spun yarn

WRAPPER FIBRES:

·        Normally, incoming fibers that have not yet been twisted in, but, in the binding -in zone, they strike an already-twisted yarn section rotating around its own axis.

·        Fibers arriving here cannot be bound into the strand:

·        They wrap themselves around the yarn core in the form of of a band , called wrapping fibers.

·        This is a typical characteristic, & simultaneously an identification feature, of rotor spun yarns. 

The number of wrapping fibers is dependent , among other things, upon :-

The position at which the fibers land on the rotor wall.

The length of binding-in zone.

The ratio of the fiber length to the rotor circumference.

The false twist  level.

The rotor rpm . &

 Fibre fineness.

Structure Of Rotor Spun Yarn :

Open end spun yarns are basically three part construction-

•          Core:                         densely packed fibers that resembles ring yarn                structure

•          Sheath:        non migrant surface fibers loosely packed around                       core.

•          Wrapper:    wrapped around the outside of the yarn .

Internal Structure

More hooked and looped fibres in rotor yarn 

Lesser migration of fibres that ring yarn due to lower tension variation

More voluminous structure, 5 -10% bulkier than ring yarn

Fibre packing not uniform, more towards yarn axis and less towards the durface .

 

 

Rotor Diameter

It influences :         yarn character                    yarn properties

                        required twist                    rotor speed & productivity

            Smaller dia:             High speed possible

                                    low energy consumption

                                    higher yarn twist required

                                    harder handle

                                    more wrapper fibres

           

            Minimum rotor dia = Staple length X 1.2

Rotor dia / Rotor Groove combination

48/43.5⁰ – denim

56/50⁰ – waste spinning material.

Rotor form & material

            Made of aluminium & steel andf partly surface treated

            Wall inclination angle smaller for higher rotational speed

Rotor Groove

            Yarn properties gets better if fibres are laid parallel, straight and           compact in groove –

                                                compactness

                                                strength

                                                hairiness

                                                handle

                                                yarn twist level generated

                                                deposition of dirt & dust

Wide groove : soft, voluminous yarn with low strength

Narrow groove: compact, strong yarn with low hairiness but hard handle

Dirt Accumulation: Wide groove, more self cleaning effect

Moire Effect : more in case of narrow groove.

Influence of Rotor Parameters on Yarn Properties

            Rotor Form &  Material

            Rotor Groove

            Rotor Diameter

            Rotor Speed

            Co.efficient of friction between fibre & Rotor

            Air flow condition inside rotor

            Liability to fouling.

TWIST INSERTATION & FIBRE MIGRATION IN ROTOR:

Concept of Spinning Delta                     Ring & Rotor

Ring: 2D, flat, Migration due to tension variation

            Fibres are position restrained

Rotor:                        Delta is PRISMATIC, hence 3D

                        More twist required so that twist is forced --- Higher                twist momentum

                        Fibres are hold by centrifugal force, hence                                     POSITIONED restrained

Higher Twist Factor---- Higher TPM---- Higher Twisting Torque---- Higher twist forced back to the spinning zone----- shorter spinning delta---- less end breakage----- stable spinning condition.

In rotor spinning migration is greatly reduced, as the fibres are FORCE restrained due to the influence of centrifugal force-

Tension difference between the fibres are very small

Still some migration takes place as the triangular spinning delta has to change to circular

This necessitates some collapse at the corners------ leads to LOCAL MIGRATION.

 

 nothing more requires ... even u hav already read better in last semester...