Rotor Spinning Machine Process

Tasks of the Rotor Spinning Machine: The basic tasks
of the rotor spinning machine are Opening (&
attenuating)
almost to individual fibers (fiber separation).
 Cleaning.
 Homogenizing through back doubling.
 Combining i.e. forming a coherent linear strand from
individual fibers.
 Ordering (the fibers in the strand must have an
orientation as far as possible in the longitudinal
direction).
 Improving evenness through back-doubling.
 Imparting strength by twisting
 Winding.

Historical perspectives of rotor spinning
•1937-The first idea and basic rotor patented by Berthelsen (Denmark).
•1951-Meimberg (Germany) developed the invention further and built
the first spinning models.
•1965-Rohlena and his group (Czechoslovakia) found the correct
combination of spinning elements and showed the first commercially
functional units in Brunn.KS200 rotor spinning machine was introduced
at 30000 rotor rpm.
1967 -The Czech firm ELITEX exhibited its rotor spinning machine
(BD200) near the international textile machinery exhibition (ITMA) in
Basel, Switzerland. The machine had a rotor diameter of 75 mm, a
rotating speed of 25,000 rpm, and a high twist multiplier (TM=6, or a
twist factor of about 5740 tpm.
 1967 Improved BD200 Rieter were presented with first mill of OE coming under
Production. Many textile machinery companies, such as Platt of UK, Rieter of
Switzerland, Zinser,Ingolstadt, Suessen, Schlafhorst of Germany, Woogay of Belgium,
Barber- colman of the USA, and so on, started to develop the new rotor spinning
machines with "air-exhausting Rotor unit.

1970 Rieter, Schubert&Salzer and Platt formed a consortium to
develop the rotor spinning Process and this resulted in the appearance
at the 1971 ITMA of a number of prototypes at various stages of
development.
invention of the twin disk rotor drives allowing higher rotor speed
(Suessen). With smaller rotors (60 mm), the rotor speed increased to
35,000 rpm.
 1971–1975 There was a considerable increase in machine
manufacturer and newer and improved version of machines was
launched with increased speed of 100000 rpm.
1975 -Witnessed Schlafhorst with Autocoro machines, which made a
mark in open-end market.
1978-Introduction of 40-50 mm diameter rotors, improved spinbox
geometries, lower yarn twist possible, first automatic yarn piecer and
package doffer fitted on the rotor spinner.
1989-Smaller rotors with speeds of 100,000 rpm.
1992-Quality yarns as fine as 13-15 Tex produced commercially at
rotor speeds up to 120,000 rpm.

1999-Rotor speeds up to 150,000 rpm possible.
2005 - Rotor speeds of up to 170 000 rpm are technically possible
without any difficulty.
 Many models appeared one after another. They are,
Rieter: BD-200M,BD-200R, BD-200RC(RCE,RN),BD-200S(SCE,SN)
and BD-SD, BDA10 (N), D-D1, BD-D2, BDA20,BD-D30.New models
R20,R40, R60, R65,and R75.
 Cangnan Jinchan Cotton Co.,LTD, has produced rotor spinning
machines:RU11,14,RU03, 04, M1/1, 2/1 and R1

Schlafhorst Autocoro 192, 216,240, 288, 312, 360 and 400.
Schlafhorst and Rieter have occupied the largest share of
world market.Besides, other rotor spinning
machines such as,SAVIO FRS of Italy, Zinser 342 and SKF of
Germany, Platt T883 and 887M of the UK and SACM-3000 of
France.
China F1603, F1604, F1605 of Jingwei Textile Machinery Co.
FA1603 and FA608 of Chuanjiang Machinery Co. in Sichuan
province.

Concept of O.E. Spinning
Continu
ous
supply
of
fibrous
feed
material
Opening
fibrous
strand to
individual
fiber state
Restoring
continuity by
depositing
individualized
fibers to the
rotating yarn

 Open End Spinning/ Break Spinning/ Free Fiber Spinning:
1. Fibrous material is highly drafted to separate out individual
fibers. They are then carried forward as free fibers (allowing them
to relax under considerable reduced drafting force before twisting)
by an air stream for spinning: Free fiber spinning.
2. Individual fibers are subsequently collected on to the open end
of the already been formed (seed) yarn. This is rotated to twist the
fibers into the yarn structure to form a continuous strand of yarn.:
Open end Spinning
3. The fiber supply is interrupted during twisting action: Break
Spinning.

•In conventional spinning ,the fibre supply is reduced to the required mass per
unit length by drafting & then consolidated into a yarn by the application of
twist.
The fibre supply is reduced, to individual fibres, which are then carried
forward on an air-stream as free fibres. This permits internal stresses to
be relaxed & gives rise to the term “free fibre spinning”. These fibres are
then progressively attached to the tail or “open end” of already formed
rotating yarn. This enables twist to be imparted by rotation of the yarn
end. Thus the continuously formed yarn has only to be withdrawn & taken
up on a cross-wound package.
Open End Spinning

Three major Commercialized Open end Spinning
methods:
1. Rotor Spinning
2. Friction Spinning and
3. Vortex Spinning (not commercialized)

Object: Overcome Limitations of Ring Spinning
Poor Economy
Low production rate
1. Low spindle speed
2. Low Efficiency
Smaller cop size
• Reduced yarn content
• Increased doffing frequency
• More number of heads
Longer production route
Low drafting capacity
Higher Pre spinning &
Post spinning Operations
Smaller size delivery package
Due to common twisting & Winding
media
• Increased doffing & creeling
• Mandatory Post spinning Operation
• Use of Heavy weight spindle
 Higher power consumption,
storage, maintenance etc.

FEEDING
OPENING
CONDENSING
TWISTING
WINDING

Tangential fiber feed into the rotor and fiber transport to the fiber collecting groove of the rotor

Feed stock : Card sliver or drawn
sliver (first or second passage).
Condenser/ feed trumpet :
Opening of the condenser can be
set to suit the hank of sliver and
avoid processing of double sliver.
Feed roller: Grips the sliver &
pushes it over the spring loaded
feed plate into the region of the
opening roller.
In the event of an end-break, the
feed unit is stopped either by
stopping the feed roller rotation
or by pivoting in feed trumpet, in
each case sliver feed stops
1. Sliver Feeding:
Feed roll: Steel roller with
helical flutes

2. Fiber Separation & Transpor
 Roller drafting is replaced
by Roller opening. It opens
fiber tufts to individual
fibers.
 Opening roller is clothed
with needles or saw teeth,
combs through the fiber
beard projecting from the
nip between the feed roller
& the feed plate.
 Trash is separated by
cleaning system and opened
fibers are transported
further for spinning.

Opening Roller:
Saw tooth clothing

Fiber transport from opening roller
to rotor :
 The suction stream in the feed
tube (transport channel) lifts the
fibers off the surface of the
opening roller & leads them to
the rotor.
 In the course of transport
movement, both the air & the
fibers are accelerated because of
the convergent form of the feed
tubes.
 This gives a second draft
following the feed nip trough/
opening roller & giving further
separation of the fibers. Moreover
partial straightening of the fibers
is achieved in this air flow.
Individualized Fiber Transport
Air flow is generated by central fan
that draws air by suction through
leads from each rotor box which is
airtight sealed.

A negative pressure created within the
rotor either by external vacuum or by
air exhausted through pumping holes
situated in the centre of the rotor;
induces the air flow through feed and
delivery tubes.
pumping holes

• The detached fibers from the opening roller pass into the
rotor groove at much higher speed to attain fiber
alignment by avoiding fiber crumpling, disorientation or
clumping together.
• Adequate air stream is used to carry forward
individualized fibers in straight and to prevent twist from
running back to drafting system.
• Unit fiber flux require the draft value at combing roller
equals to number of fiber in the cross section of sliver;
nearly equals to ten thousand. In practical term fiber flux
is always more than unity but should not be too high.
4. Fiber collection / allignment
Fiber collection in the rotor groove: The centrifugal forces in the
rapidly rotating rotor cause the fibers to move from the conical
rotor wall toward the rotor groove and be collected there to form
a fiber ring.

A third draft arises upon arrival of the
fibers on the wall of the rotor because
the peripheral speed of the rotor is
several times as the speed of the
fiber in transport tube.
The last straightening of the fibers
occurs as the fiber slides down the
rotor wall into the groove under the
influence of the enormous
centrifugal forces work within the
rotor. This draft contributes
significantly to good orientation of the
fibers.
4. Fiber collection / allignment

Fibers entering rotor groove from
transport duct are having 80% speed of
this rotating body, gives fourth draft
normally of the order of 1.25 and 1.4.
Sufficient to lay fibers in straight
configuration in the rotor groove. This
can integrate fiber with yarn structure in
straight configuration results in
maximum utilization of fiber strength.
Fibers entering the rotor are deposited on
the internal sliding wall) and move on
this surface to rotor groove in parallel
and straight fashion to form fiber ring.
The sliding wall is the part of
the transit system; surfaces
must be well designed and
should be kept clean. The
sliding movement of the fibers
gives cleaning of this surface

Real twist is applied to the yarn by the motion of the
rotor acting on the yarn arm that passes from the rotor
groove to the yarn withdrawal point inside the rotor.
One rotation of rotor inserts one turn of twist into the
yarn length (in inches) withdrawn from working region
in that time interval.
Fibers are not firmly gripped at the peeling off point in rotor by
any discrete nip.Thereby twist usually runs back to rotor groove
and some fibers are laid onto an already twisted core of fibers.
This affects yarn structure
5. Yarn formation / Twist insertion

 Yarn arm speed = Rotor
speed; until take up is not
started.
 Parallel rotation
generates turns of twist
 Distributed between
navel & take up roller;
also slip past to yarn arm
in absence of firm grip at
navel; helps in piecing.
 Yarn arm speed = Rotor
speed + take up speed;
 Difference causes peeling
of fiber ring.

 Gives pathway for yarn
withdrawal from the rotor.
 It deflects seed yarn path by
90o.
 Separator plate is introduced
sometime to prevent
premature capture of the
incoming fibers by the
outgoing yarn.
 The yarn emerging the navel
rolls on the inside surface.This
rolling action inserts a false
twist in the section of the yarn
Navel

A = Centrifugal force acting
on yarn
B = Yarn withdrawal force.
Due to these two opposing
forces acting on seed yarn
it is pressed against the rim
of the navel.
Rotor rotates in clockwise
direction.
Yarn arm rotates in clockwise
direction just like epicycle gearing.
Yarn arm speed is always higher
than rotor as it is an outcome of
rotor speed & yarn pull.
The yarn arm is rotated around the
inner wall of navel through the
rotation of the rotor, the frictional
force ( R) is exerted on the yarn.
Frictional force (R ) creates a
torque in the yarn pressing it
against the navel and thereby
creates false twist.

 Yarn is withdrawn through doff tube towards take up
shaft.
 Angle of withdrawal ∞ SpinningTension between doff
tube and take up roll.
 Angle of withdrawal: 30, 60 & 90.
 Winding: Traversing + Grooved drum +Waxing device.
 Product: Cone or Cheese.
 Take up tension = 10 to 20% of spinning tension.
Yarn formation: When a spun yarn end emerges from the
draw-off nozzle into the rotor groove, it receives twist from
the rotation of the rotor outside the nozzle, which then
continues in the yarn into the interior of the rotor. The yarn
end rotates around its axis and continuously twists-in the
fibers deposited in the rotor groove, assisted by the nozzle,
which acts as a twist retaining element.

Yarn take-off, winding: The yarn formed in the rotor is
continuously taken off by the delivery shaft and the
pressure roller through the nozzle and the draw-off tube
and wound onto a cross-wound package. Between takeoff
and package, several sensors control yarn movement as
well as the quality of the yarn and initiate yarn clearing if
any pre- selected values are exceeded.

Principle of Rotor Spinning:
1. Input: Drawn sliver is drawn through condenser and fed to the
drafting system by a feed roller operating in connection with
feed pedal.
2. Drafting & Fiber Transport: A sliver with 20,000 or more fibers
in its cross-section use for the production of a yarn with 100
fibers per cross-section; will require a minimum total draft of
200. This amount of draft is substantially higher than that of
ring spinning. This is accomplished by using a comber roll (pin/
saw tooth) which opens the input sliver to almost individual
state and also releases trash entrapped. Separated trash is
collected in central chamber from where it is periodically
removed. Transport tube sucks fibers from the opening roller
and transfers on to the inner grooved periphery of rotor
by an accelerating air stream (gives air draft). These two
operations produce an amount of draft that is high
enough to reduce the 20,000 fibers entering the comber
roll down to few fibers (5-10 fibers).

Advantages offered by Rotor Spinning:
1.Lower power consumption per unit
quantity of yarn produced.
2.Higher speed of twist insertion
resulting in very high yarn delivery
speed
3.A significant increase in productivity
4.Larger delivery package size
5.Elimination of pre spinning processes
like speed frame and post spinning like
winding
6.More uniform quality of yarn due to
higher doubling.

Twist in Yarn
• Twist / metre=rpm of Rotor/ withdrawl
speed {l}.
• The spun yarn is withdrawn through a
passage in the navel “ T” which rolls
continually on naval.
• The partial rolling of the yarn gives rise to
false twist between the twisting-in point
{G} for the fibres & the navel {T}.
• Twist level between “G to B” is 20-40%
higher than those at navel.
• Yarn tension is generated by the withdrawl
rolls during withdrawl in opposition to the
centrifugal force in the rotor.
• Tension is highest at the withdrawl rolls
themselves & declines towards rotor wall.
• The yarn tension & twist level are inversely
proportional .

Formation OF The Yarn
• The yarn end is pressed against the rotor wall by the high centrifugal force,
& the separation point therefore rotates within the rotor . Each revolution
of the yarn at this point inserts one turn of twist.
• The yarn twist penetrates into the fibre ring in the collecting groove,
where the fibres are to be bound together to form a yarn.
• The length of this binding in zone is of some significance for the spinning
conditions & the the yarn characteristics.
– Too short length - high ends-down rate
– too long length - twisting-in will be very tight , & there will be many
wrapping fibres

Wrapping Fibres
• Normally , incoming fibres 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.
• Fibres arriving here can not be bound into the strand:
• They wrap themselves around the yarn core in the form of of
a band , called wrapping fibres.
• The number of wrapping fibres is dependent upon :-
• The position at which the fibres land on the rotor wall.
• The length of binding-in zone.
• The ratio of the fibre length to the rotor circumference.
• The false twist level.
• The rotor rpm
• Fibre fineness.

Fibers have some freedom of movement during
twist insertion, the outer fibers tends to slip more
than the core fibers.
O.E. Yarn structure is thereby made up of three parts:
i. Densely packed core consisting of about 80% of
fibers substantially aligned with the yarn axis.
ii. Loosely packed fibers twisted around the core at
an angle to the axis; and
iii. Wrapper fibers on the outside

Structure of Rotor Spun Yarn
Wrapper fibers
Loosely packed fibers
Densely packed core
1. The core contains
densely-packed fibers
similar to ring-spun
yarns.
2. Sheath fibers are
loosely packed round
the yarn core at a low
angle to the yarn axis.
3. The wrapper or belt
fibers are wrapped
around the outside of
the yarn at a very
large inclination to the
yarn axis.
4. Fiber migration in
rotor yarn is relatively
local: fibers in each
layer are only tied to
the fibers of adjacent
layers.

 Wrapper fibers : Improves yarn
abrasion resistance but
Reduces wicking properties of
yarn.

Figure shows the surface structure of typical rotor yarn. The core contains
densely-packed fibers similar to ring-spun yarns. Sheath fibres are loosely
packed round the yarn core at a low angle to the yarn axis. The wrapper or belt
fibres are wrapped around the outside of the yarn at a very large inclination to
the yarn axis. It has been reported that fibre migration in rotor yarn is relatively
local: fibers in each layer are only tied to the fibers of adjacent layers. Rotor
spinning generates lots of hooks and looped fibers even if a well parallelized
sliver or roving is fed into the rotor. The typical distribution of fibers shapes in
rotor-spun yarn the yarn is: 39% folded or buckled fibres in the core, 31%
straight fibres in the core, 15% leading hooks and 15% trailing hooks in the
outer layers.
Given its structure, fibers in rotor yarn are less packed than ring yarn. Rotor
yarns are known to be 5-10% bulkier than ring yarn. Across the cross-section,
the packing is not uniform. The packing is maximum at a point approximately
one third to one quarter of yarn radius from the central axis. This has been
attributed to greater buckling if fibres in the core. As a result, packing of
rotor yarn is concentrated nearer the yarn axis and less towards the outer
surface of the yarn in comparison to ring yarn.

Rotor spun yarn is less strong than comparable ring spun yarn. This is because of
the straight, parallel arrangements of fibers and denser packing of fibers in ring
spun yarn which contrast with the higher numbers of disoriented folded fibers in
rotor spun yarn, lower levels of fibre migration, less packing and the presence of
non-load bearing wrappers and belt fibres.
Rotor spun yarns are generally more extensible than ring spun yarns. The
higher breaking extension of rotor yarn is due to presence of a lot of hooked,
looped and disoriented fibers in the structure. However, the dense, more
tangled structure of fibres in the core offers very little freedom of movement
of fibres in rotor yarns. Rotor yarns are therefore less flexible than ring yarns
which have a more uniform helical arrangement of fibres.
Due to its unique structure, rotor yarn shows higher abrasion resistance than
ring spun yarn. The loosely-wrapped sheath fibers can easily yield to an
abrasive surface, and, given its greater bulk, the yarn can flatten, giving
further abrasion resistance. Rotor yarns also have fewer irregularities and
imperfections compared to carded ring-spun yarns. This has been attributed
to the mechanism of yarn formation, i.e. back doubling in the rotor groove
before twist insertion which irons out irregularities.

Fiber Integration
During Rotor Spinning

Various Types OF Binding Fibres
• Class 1 fibre :- The yarn tail picks up the trailing end of a fibre which lies
wholly on the surface of the rotor. The fibre is integrated into the yarn &
tends to take a helical form, which will be distorted by migration. The original
fibre direction is reversed. This fibre is called as class1 fibre.
• Class 2 fibre :- The fibre is just emerging from the transparent tube as the
yarn tail sweeps past. The leading end of the fibre is picked up & moves
towards the centre ; the trailing end is flung onto the surface of the rotor ;The
fibre becomes a “bridging fibres”. I.E., Fibres that bridge the gap that should
theoretically occur behind the pick-up point, p. The fibre is integrated in the
yarn & tends to take a helical form as in class 1, but there is no change in
fibre direction. This fibre is called as class 2 fibre.
• Class 3 fibre : A fibre that has partly emerged when the yarn tail arrives : the
leading part is on the surface of the rotor ; the trailing part is tube. The fibre
is picked up at some point along its length. The leading end is integrated in
the reverse direction . the trailing end is integrated in the forward direction. A
leading hook is created. This fibre is called as class 3 fibre.

Class I fiber
Yarn arm picks up the trailing
the fiber that is straight & lies
on the surface of the rotor
the yarn arm sweep past
 Attain helical configuration
twisting.
 Goes to the core under
tension
 Original fiber direction gets

Class II fiber
Yarn arm picks up the leading
of the fiber that is just
out of the transport tube as the
yarn arm sweep past
 Attain helical configuration
twisting.
 Original fiber direction does
get reversed.
 Fiber acts as bridging fiber
 Since fiber tension is not
up initially twisted loosely
surface and then on gradual

Class III fiber
Yarn arm picks up the fiber
is partially emerged out of
transport tube as the yarn
sweep past
 Front end behaves like
attain helical configuration
on twisting and original
direction gets reversed.
 Part next to pick up point
as bridging fiber; class II
 Creates leading hook

The probability (P) of fiber’s
falling into class III depends on
1. Fiber length/ fiber extent (E)
&
2. Circumference of the rotor
(∏D).
As P (%) = (100E) / (∏D)
• Shorter fibers are less likely
to fall in class III. &

 If ∏D < E; yarn arm would pass through the
fiber entry zone at least twice during the
period that the fiber was being peeled off;
this will surely brings ends down.
 Higher production rate demands working
with smaller Rotor diameter (D);
 Restricts processability of long fine fibers. Or
else results in higher number of wrapper fibers
with higher number of wrappings. – Poor yarn
quality
 With condition ∏D > E; spins short fibers
efficiently; thereby spinning of finer yarn count

RotorYarn structure depends on
the mode of integration of Class
I-III fibers.
Class I fibers: firmly embedded
with rotor groove at the point of
pick up & integrated into yarn
under due tension; goes to core.

Class II fibers: Starts to be integrated
while still lies mainly inside the
transport tube or before coming
under the influence of rotor or its
centrifugal force.Tension within the
fiber is low & thereby starts as loosely
wound surface fiber.
Its trailing end is withdrawn
progressively from the tube, it makes
increasing contact with rotor surface,

Class III fibers: Picked up at some
point along its length, leading part
being pressed onto the rotor surface
by centrifugal force & trailing part is
still in the tube.
Forms leading hook
Original leading end being under
tension enters the core of the yarn.
Original trailing end starts on the
surface but works its way into the

Open end spun yarns are basically of a
three part construction due to presence of
class I –III fibers and their difference in
behaviour at the point of integration.
1. Core: It is made up of substantially
twisted straight fibers
2. Sheath: Loosely wound fibers with
low twist angle
3. Tightly wound belts.

Machine & Process Variables of
Rotor Spinning

Machine Variables
1. Feed Unit
2. Opening Roller
3. Transport Duct
4. Rotor
5. Navel

a = opening roller,
b = feed plate,
c = feed roll,
d = Fixed beard
support,
e = Trash ejection,
f =adjustable bypass
 Additional grip from Fixed beard support (d) used
at High speed Rotor unit.
 Controls variations in thickness of sliver.
1. Feed Unit: Feed Plate (b) + Feed Roller (c)

Feed Roller
• A fluted feed roller –Diagonal flutes
• To increase the clamping effect
• The distance must be decreased for finer feed sliver or smoother fibres or
both.
• The opening roller rotates between 5000 & 10000 rpm, usually between 6500
& 8000rpm. Higher speed –Coarser Yarn , Slower speed – finer yarn
• Drafts of up to 2000.
• Diameter - 60 & 80mm

Performance of opening roller is decided
by
a) Type of teeth.
b) Teeth specifications ( Rack angle, Pitch/density,
Height).
c) Surface speed of opening roller.
d) Condition of teeth.
2. Opening Roller

A) Types of teeth : a) Pin type and b) Saw tooth
type.
Pin type Saw tooth
higher wear resistance,
longer life
higher wear resistance,
longer life
It results in fewer fibre
breakages especially at
high opening roll speed
It results in higher fibre
breakages
Fibre removal from
opening roller to
transport tube is difficult.
Ease of fiber transfer
irrespective of opening
roller speed.
More difficult to
manufacture
Easy to manufacture
Does not offer the wide Wide range of tooth

 B)
 Tooth Height (h) ∞ Intensity of combing
action
∞ Better individualisation and
trash removal Higher “h” should be
preferred for coarse trashy cottons.
 Lower height should be used gentler action
but fibre individualisation will be inferior.
h
d

Rake angle (a)
Rake angle is the angle made by front edge of teeth
with horizontal.
 Action of opening roller will increase as rake angle reduces and at
the same time fibre breakages will increase.
Clothing rake angle
 66 to 80° for cotton and
 90° and above for synthetics.
 Coarse cottons with higher trash, opening roller with
lower rake angle is preferred.
 Finer cottons higher rake angle
a
b
h
d

Tooth Pitch/ Point Density (b)
• Higher pitch, reduces density and drops
intensity of combing action.
• Lower pitch increases PPSI and ensures
better individualisation as well as trash
removal. It should be preferred for coarse
trashy cottons and higher opening roll
speed.
• Lower pitch should be used for higher
opening roller speed to reduce opening

Decoding of tooth
1. Application Field
B – Preferred field of application for cotton
S - Preferred field of application for Cotton & Man
made fibers
2. Tooth shape
The number after the letter is representing tooth
shape code number
3. Material
DN – Diamond coated & Nickel plated
D – Diamond coated
No symbol used – Nickel plated

• Standard tooth type used for
opening roller.

• Opening roller used mainly for cotton

• Universal Opening roller
• Wide application range but primarily used for
manmade fibers and their blends with cotton

Higher opening roller speed results in;
• Better sliver opening.
• Better trash extraction.
• Fewer imperfections like thick and thin places in
the yarn.
• Higher Production rate
But also
• More dust formation.
• More fiber damage.
• Reduce the yarn strength.
C) Opening roller Speed

The opening roller speed should be
increased when there is inadequate trash
extraction.
The opening roller speed should be
decreased when too many good fibers are
removed with high proportion of short fibers.
The speed of the opening roller depends on
the fiber material and opening roller type.
The service life of the opening roller can be

Excessively high opening roller speeds
result in:
 More or less severe damage to – i.e.
Shortening of – fibers, and thus
 Losses in yarn tenacity and the strength of
the fabrics produced from them,
 An increase in fiber fly on the spinning
machine and in downstream processing,
 melting points when processing man-made
fibers.

Opening roll Speed
Optimum speed depends upon fibre and its properties.
Optimum roller speed is around
 8000 to 9000 rpm for coarse and trashy cottons,
 7000 to 8500 for long staple cottons and
 6000 - 7000 for man-made fibres.

Trash-removal devices
• The high peripheral speed of the opening
roller causes the coarser trash particles to
be hurled outwards at this position [a]
while the fibres continue with the roller &
pass into the feed tube [b].
• · The trash removal depends upon :
• The design of the assembly.
• The air-flow conditions.
• The degree of opening of the feedstock.
• The speed of rotation of the opening roller.

BY pass open (maximum trash removal) BY pass half open (medium trash removal)
BY pass closed (minimum trash removal)
Setting for Trash Removal

• Combing out will be more intensive & even if:
 The thinner the fibre strand {sliver fineness},
 The more parallel the fibres arrangement
 The more highly straightened the fibres,
 The smoother the fibres [lustrous or delustred] ,
 The shorter the clamping distance
 The optimum rotational speed of the roller high roller speed will
damage the fibres while lower roller speed would deteriorates
yarn quality

Transport tube:
 After opening the fibers must be supplied to
the rotor. Transport tube; a closed fiber
channel in the shape of a flow passage
serves as a means of guidance.
 Centrifugal forces of the opening roller and a
vacuum in the rotor housing cause the fibers
to disengage from the opening roller.
 Transport of the disengaged fibers through
the fiber channel to the rotor is effected by an
air current generated by suction of air from
3. Transport Tube

Velocity profile of air in the opening roller to
transport tube junction
 Velocity of the air in the opening roller near transport
tube increases in the radial direction from the
opening roller towards wall of transport tube and as
a result, pressure reduction occurs in the radial
direction away from opening roller teeth.
 This helps in removing the fibres from the teeth to
the high velocity air stream rushing into transport

In order to achieve satisfactory doffing and
transportation, velocity of air must be 1.5 - 2
times circumferential velocity of opening
roller.
too high or too low ratio of circumferential
velocity of opening roller to airflow velocity is not
conducive to good quality of yarn due to
recirculation of air at outer cover side or opening
roller side.

SPEEDpass:
This is an additional opening in the fiber guide
channel through which a certain proportion of the
fiber transport air is extracted in order to increase
the air volume and thus the rate of flow in the fiber
guide channel.
• Promotes the disengagement of fibers from the
opening roller clothing and suitable for processing
man-made fibers and blends containing more than
50% man-made fibers.
• Higher volume of air proves beneficial in the
manufacture of coarse count yarns or for high
material throughput.
• Cotton dust (finishing abrasion in the case of man-
made fibers) is also extracted through this
opening. Fine dust therefore does not accumulate

Fiber guide channel (a) with SPEEDpass (b)

•There is one with SPEEDpass
available for spinning man-made
fibers and coarse cotton yarns.
•The SPEEDpass permits more air
to be pulled through the fi ber
channel.
•This enhances the fiber
separation at the opening rollers
and the stretched transport of the
fibers into the rotor.
•Residue is removed from the
material flow over the SPEEDpass.
•As a result, the rotor grooves,
which impact the yarn quality
decisively, remain clean.
•Highest performance for
productivity and yarn quality

Important terms:
Spinning Stability: Spinning desired yarn quality
without causing end break or by imparting due control
interference factors (trash particles, foreign fibers,
accumulation etc.) which can result in a yarn break.
If more disruptive effects are endured with yarn
than spinning stability is said to be poor.
Minimum Spinning twist (αmin): It represents
minimum degree of yarn twist required after piecing at
given constant delivery speed to continue with spinning
without deteriorating yarn quality and causing end
other way round the level of twist up to which spinning
possible or stable.

Thus material and surface characteristics of rotor are prime
important for defining false twist insertion and thereby rotor
yarn quality.

surface of the draw-off nozzle due to the rotation of
the rotor. This rolling-off temporarily inserts
additional twist into the yarn (contrary to the
direction of twist of the yarn), thus creating the
false-twist effect required for spinning stability,
which can be up to 60% of the set yarn twist. The
greater the false-twist effect, the higher the spinning
tension.
 While rolling off on the surface of the nozzle, the
yarn is repeatedly raised briefly in rapid succession,
depending on the surface structure. This high-
frequency vibration – together with the false-twist
effect – promotes twist propagation into the rotor
groove. The more pronounced the structure of the
nozzle surface, the more vigorously the yarn

Yarn twist in rotor spinning
is normally produced
outside the rotor between
draw off nozzle (A) and
subsequent yarn
deflection or Nip point
(U). But it continues from
there against the yarn take
up direction into the yarn
arm within the rotor up to
yarn peel off point (P)
and beyond that another
few millimeters into the
mini sliver (fiber ring) in
the rotor groove.

Twist-in zone length lE
i. Yarn twist should be diffused up to peel off point and a
few millimeters beyond into the rotor groove (PTE
zone) for reliable and continuous spinning.
ii. Higher the twist penetrates into the rotor groove, the
more reliably the fibers deposited get spun in without
small interruptions being able to cause end break.
iii. The PTE length is approx. 2 – 12 mm.

The rotor is the main spinning element of the rotor spinning
machine.
•Yarn qualities, operating performance, productivity, etc., all
depend chiefly on the rotor.
•The most important parameters of the rotor that exert influence
are the inclination of the rotor wall (a); the coefficient of friction
between the fibers and the surface conditions of the rotor wall
(b); the design and the positioning of the rotor groove (c); rotor
groove diameter (d) and rotor speed.

Direct rotor bearing, with rotor shaft (a) encased
in ball bearing housing (b)
Support-disc bearing (Twindisc
bearing) with rotor fitted

Support-disc bearing (Twindisc bearing) with
pressure roller (b) for tangential belt (a)
Axial rotor bearing with magnetic bearing
– Positioning the magnetic bearing

Axial rotor bearing with EC bearing Sealed grease cup of the EC bearing
Axial rotor bearing with AERO bearing Airflow with the AERO bearing; air
pressure 6 bar

•The rotor, consists of rotor shaft (a) with wear protection in
some cases,
• Rotor cup (b) with rotor groove (C) and rotor wall (d).
• The wall inclination is necessary so that fibers emerging from the
feed tube and passing to the wall can slide downward.
•Depending upon the material and area of use, the angle of the
rotor wall to the vertical ranges between 12° and 50°
•This angle is dependent upon the make but will in all cases be
smaller, the higher the rotation speed for which the rotor is
designed.
• At the internal periphery in the lower region of the rotor cup,
• There is usually a groove that varies in width. This groove serves
to collect fibers.

•Rotors are made of steel and are in general surface-treated or
coated to give them a longer useful life.
•The following means, which are customary and proven in mill
practice, are available for protecting rotors against wear:
•diamond/nickel coating; The diamond coating usually consists of
diamond dust embedded in a nickel layer and is the same as that
used for protecting the opening rollers against wear.
•boron treatment; or a combination of both processes.
•Boronized rotors and boronized rotors with an additional layer of
diamond coating have twice the lifetime of a diamond-coated
rotor.
•However, the surface structure of the rotor wall changes
depending on the type of treatment (boron or diamond
coating), and thus also its influence – which should not be
underestimated – on both yarn quality and spinning stability
and the tendency for deposits to form in the rotor groove.

•The best possible compromise between long service life of the
rotor, good yarn values and stable spinning conditions is achieved
with the combined boron/diamond coating. The rotor is a part
subject to wear and must therefore be replaced periodically. Wear
mainly affects the groove.
•The configuration of the rotor groove determines
•whether the yarn is bulky or compact, hairy or lean,
•and whether the yarn quality is excellent or only adequate and
the spinning stability low or high.
•The groove also affects the extent to which dust and dirt tend to
accumulate in the rotor.
•Depending upon the raw material used, the desired yarn
characteristics and yarn values, different groove designs are used
in practice.

•Wide grooves produce a soft, bulky yarn with rather low
Strength.
•used in the production of yarns for knitted fabrics, homespun-
type fabrics and coarse articles.
•While narrow groove produce a compact, strong yarn with low
hairiness.
•used for yarns required for the production of stronger fabrics
with a smooth appearance.
• A fairly narrow groove is in most wide-spread use in classical
short staple mills. The tendency to form more effects is also
greater with the narrower groove, because fairly large dirt
particles can jam in the groove.
•A speed range in which the rotors produce optimum results, in
terms of technology, spinning stability and energy consumption.

Following parameters have effect on spinning:-
 Rotor diameter
 Rotor speed
 Rotor groove shape
The quality of rotor spun yarn is influenced by the rotor
specifications and speeds. When the rotor speed is too
high, the tension during spinning increases and progress
of twist in rotor groove is impaired. Soil particles easily
gets embedded in rotor groove due to high centrifugal
force, causing yarn breakage.
Where as low rotor speed results in reduction in yarn
tension, which adversely affect the false twist function on
the delivery nozzle, further results in end breakage.
Rotor

The probability (P) of fiber’s falling into class III
(wrapper fiber formation) depends on
1. Fiber length/ fiber extent (E) &
2. Circumference of the rotor (∏D).
As P (%) = (100E) / (∏D)
 Accordingly bigger rotor diameter reduces
number of wrapper fibers; but generation of
higher centrifugal force and thereby higher
false twist increases their number of
wrappings.

 Rotor diameter is dictated by the staple length of
fiber.
 Normally rotor diameter should be at least 1.2
times that of fibre length.
 Optimum circumference of the rotor in relation to
fiber length is about 3 to 5 times.
Staple length (inches) Rotor Diameter
(mm)
Long staple (exceeding 64
mm)
60 - 100
Short fiber (38 to 64 mm) 50 -60
38 mm and shorter 40 -50

Yarn Count (Ne) Rotor Diameter
(mm)
4.5 to 14 40 and above
16 to 20 36
24 and above 33

Rotor diameter ∞ Rotor
speed-1.
Technological problems at higher rotor speed
1. The tension on the yarn should not be allowed to exceed
20% of the yarn breaking load
Tension F2 acting on yarn = (n.D)2 ; Where
n = rotor speed
D = rotor diameter
Rotor
Diamete
r (mm)
Rotor Speed
(rpm)
50 and
above
50,000
40 -50 65,000 to
36 Up to 90,000

Rotor diameter ∞ Rotor
speed-1.
2. Surface speed of rotor wall where the fibers are landing
should have a certain optimum constant vlaue.
Keeping n.D constant, ensures that the circumferential speed
of the rotor remains constant
3. Force with which fibers are driven from slip surface (wall)
to groove should be kept constant.
4. Centrifugal force acting on the fiber band in rotor groove
should also remain constant.
Keeping n.D constant does not ensure that centrifugal force
acting on fiber band also remain constant.

• Yarn Strength: Bigger Diameter leads to higher
centrifugal force acting on yarn arm, which
increases wrappings and makes yarn more
compact. Thereby makes yarn
Stronger
Less hairy
Small diameter
• Yarn Elongation: Drops markedly with increase
in diameter.
Due to compact structure.
Increases end breaks at peel off point
Effect of Rotor Diameter on yarn properties:

Yarn Regularity: U% and thick and thin
places are not much affected, but neps
increase markedly with increase in rotor
diameter.
 Increase in irregularity due to higher
centrifugal force gives higher wraps per
unit length of wrapper fibres is well
compensated by the improvement from
back doublings with higher diameter and
as a result U% is unaffected.
 Neps increase with rotor diameter because

Higher spinning speed due to a
correspondingly higher rotor speed
Lower energy consumption
Higher yarn strength
Less yarn hairiness
Smaller yarn diameter
Reduced spinning stability, more yarn
breaks
A reduction in rotor diameter
results in:-

The rotor diameter is increased, steep increase in nep
level will be observed.
Bigger rotor diameter
Higher centrifugal force
Higher false twisting at rotor zone
Higher Untwisting after navel makes wrapper fibers
intensively wrapped earlier to strip back results in an
increased linear density. Such portion of yarn is
accounted as nep.

Energy consumption ∞ Spinning tension ∞ Rotor
diameter.
• Spinning tension F (cN) = k1 R2 n2 t
Where; k1 is a constant, t = Yarn linear density (tex)
R = Rotor groove radius (m), n = Rotor speed (rpm)
Higher tension leads to higher end break
• Smaller rotor diameters should be used at
higher rotor speeds.
Rotor Diameter (mm) Rotor Speed rpm
33 75000-130000
36 60000-120000
40 55000-100000
46 80000-95000
56 65000-75000

2. Rotor speed:
Influence on
 Productivity: Higher the rotor speed higher the input
(feed) & output (delivery) speed.
Production ∞ Rotor speed
Influence on Process Proficiency:
Increase in Rotor Speed
 increases False twist; Results in more often winding of
wrapper fibers with reduced αmin. and thereby higher spinning
stability up to certain extent.
 Higher centrifugal forces on the fibers in the rotor groove
increases spinning tension & results in end break.
Lower rotor speed
 Low power consumption & production as well as Poor spinning

Effect of rotor speed on yarn quality;
A. Yarn strength & elongation:
 Higher the rotor speed, higher will be the centrifugal
force by which fiber-ring is pressed in the rotor groove.
 This require higher peeling force and thereby yarn
tension. Higher yarn tension improves fiber
orientation & thereby increases yarn strength.
 Higher the centrifugal force, more will be the number
of wrapper fibers as well as their wrappings, increases
yarn compactness and thereby yarn strength.
 Higher fiber stress at higher yarn tension and
increased number of wrappings sacrifices yarn
extension.

B.Yarn Evenness, imperfections and appearance grade:
Higher the rotor speed;
1. Reduced Degree of combing: Rate of feeding increases
but not the opening roller speed.
• Reduced draft between feed roller & Opening roller:This
gives loss in combing roller efficiency in fiber
individualization, trash removal efficiency, deteriorates in
yarn evenness, imperfection and appearance grade.
2. Steeper increase in nep level:Wrapper fibers and their
wrapping intensity increases with rotor speed due to
increased centrifugal force. At the point wrapper fibers
occurs, the yarn has a higher linear density because of
greater fiber mass wrapped round the yarn and such
places are counted as neps in rotor yarn.

Requires: For each rotor diameter there is a
speed range in which spinning, is possible.
 Too low a rotor speed results in poor
spinning stability, since due to excessively
low yarn tension, the yarn twist cannot
adequately penetrate to the rotor groove.
 Too high rotor speed also results in poor
spinning stability de to the effect of
powerful centrifugal forces on the fibers in
the rotor groove, but also due to

Increased spinning speed
Decreasing elongation at break
More imperfections
Improved spinning stability
With identical rotor diameter, an
increase in rotor speed results
in:-

3. Rotor Groove:
Important parameters:
i. Groove radius
ii. Groove angle and
iii. Groove surface roughness.
The configuration of rotor groove has a
pronounced effect on:
i. Spinning stability,
ii. Rotor groove dust loading &
iii. Yarn quality.

 Rotor with more open and smooth groove
offers better twist penetration resulting in
good spinning stability and bulkier yarn.
 Coarser yarns produced usually from inferior
cotton results in higher trash deposit in rotor.
So larger groove diameter is more suitable.

Shapes of Rotor Groove
1. S- shape: Sharp edge without groove.
• Suitable for dirty cottons and coarse
counts.
2. G- Shape: rotor with narrow groove.
• Suitable for fine counts with clean back
stuff (cotton) as they are difficult to be
cleaned. Recommended for knitting.
3. U-shape: Rotor with wide groove.
• Suitable for coarse count. Gives higher
strength than S-type but more susceptible
to moire effect due to partial soiling with
higher trash.

Material of RotorWall / Surface characteristics of rotor:
The roughness of the rotor wall is determined by rotor
coating.
 A rough surface rotor gives higher yarn quality but
too much roughness with a small wall inclination
angle adversely affects spinning stability.
Material:
i. Made up of steel and surface hardened.
ii. Different coatings are used for protecting against
wear;
iii. Diamond coated gives better yarn quality but
difficult to clean with shorter shelf life.

Rotor Spinning Machine Process

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