1
Spinning:
Spinning could be defined as:
ü The
drafting and, where appropriate, the insertion of twist in natural or staple
man-made fibers to form a yarn.
ü The
extrusion of filaments by spiders or silkworms.
ü The
production of filaments from glass, metals, fiber-forming polymers or ceramics.
1.1
Spinning techniques:
Different spinning techniques
still used are:
1. Break Spinning: Sliver feed stock is
highly drafted and assembled at end of rotating yarn.
2. Rotor Spinning: Individual fibers
converted to yarn through rotary motion.
3. Friction Spinning: External surface of
two rotating rollers is used twist individual fibers into a yarn.
4. Air-jet Spinning: Utilizes air to apply
the twisting couple to the yarn during its formation.
5. Centrifugal Spinning: A method of yarn
formation involving a rotating cylindrical container.
6. Dispersion Spinning: Polymers are
dispersed in a carrier solution and extruded from carrier.
7. Draw-Spinning: Orientation is
introduced prior to the first forwarding or collecting device.
8. Dry Spinning: Dissolved polymer is
extruded by evaporation of solvent.
9. Flash Spinning: Polymer is extruded at
a temperature well above the boiling point of the solvent.
10. Flyer Spinning: Yarn passes through a
revolving flyer leg guide on to the package.
11. Melt Spinning: Conversion of a molten
polymer into filaments by extrusion and cooling.
12. Reaction Spinning: Polymerization is
achieved during the extrusion of reactants.
13. Ring Spinning: Twist is inserted in a
yarn by using a revolving traveler.
14. Wet Spinning: Dissolved polymer
converted to filaments by extrusion into a coagulating liquid.
1.2
Ring spinning technique:
Fiber material is supplied to the
ring-spinning machine in the form of roving. The fiber mass of the roving is
reduced by a drafting unit. The twist inserted moves backwards and reaches the
fibers leaving the drafting unit. The fibers lay around one another in
concentric helical paths.
It is the process of further
drawing out roving to the final yarn count needed, inserting twist to the
fibers by means of a rotating spindle and winding the yarn on a bobbin. These
three stages take place simultaneously and continuously.
A mechanically driven spindle, on which the yarn package firmly
sits, is responsible for twist. A
stationary ring is around the spindle, which holds the traveler. Yarn from
the drafting unit is drawn under the traveler, and then led to the yarn
package. In order to wind the twisted yarn on a bobbin tube carried by the
spindle, the traveler is required to
cooperate with the spindle. The traveler moves on the ring without any physical
drive, but is carried along by the yarn it is threaded with. The rotation rate
of traveler is lower than the spindle, and this difference in the speeds of
traveler and the spindle enables the winding of the yarn on the tube. A
controlled up and down movement of the ring determines the shape of the yarn
package, called Cop or Bobbin.
1.2.1
Properties:
Yarn properties depend on raw
material used, twist, fiber length, fiber density, individual fiber strength
and many more basic terminologies but generally ring spun yarn has following
properties:
ü Strongest
yarn
ü Finest
yarn
ü Softest
yarn
ü "Z"
and "S" twist
ü Lowest
productivity
ü Most
uneven
ü Most
expensive
ü More
hairy, generally
ü More
torque
ü Widest
range of yarn counts
1.3
Advantages and disadvantages of ring spun:
1.3.1
Advantages of Ring Spun:
ü Production
of high strength yarns.
ü Spinning
of fine count yarns.
ü Proper
for special yarns.
ü It
is universally applicable (any material can be spun).
ü The
know-how for operation of machine is well established accessible to everyone.
ü It
is flexible as regards quantities (blend and lot size).
ü Since
the speeds in drawing section are best controlled, yarn evenness is excellent.
But if short fibers are too much, yarn unevenness occurs.
ü Fine
yarns can be produced as compared to open end system
1.3.2
Disadvantages of Ring Spun:
ü Process
stages are more numerous. Roving stage exists as an extra process compared to
the other systems.
ü Yarn
breakages are more numerous as a result of ring traveler friction and yarn air
friction.
ü Interrupt
ions, broken ends and piecing up problems exist because of the yarn breakages.
ü The
high speed of the traveler damages the fibers.
ü The
capacity of the cops is limited.
ü Energy
cost is very high.
ü Low
production rate.
ü New
spinning processes have difficulty in gaining widespread acceptance. Owing to
their individual limitations, the new spinning processes are confined to
restricted sectors of the market.
ü The
ring frame can only survive in longer term if further success is achieved in
automation of the ring spinning process. Also, spinning costs must be markedly
reduced since this machine is significant cost factor in spinning mill.
1.4
End uses:
End uses depend on the raw
material used, count, fiber length and such other properties of yarn but
generally ring spun yarns are used in T-Shirts, Socks, Sports Wear, Other woven
and knitted products, Bed sheets, Underwear, Towels and Bathrobes.
2
Rotor spun yarn:
Rotor spun yarn method uses a
rotor to collect individual fibers into a yarn. The fibers on entering a
rapidly rotating rotor are distributed around its circumference and temporarily
held there by centrifugal force. The yarn is withdrawn from the rotor wall and,
because of the rotation, twist is generated. Its process flow chart and
spinning technique is as:
2.1
Process flow chart:
Fiber/Bale → Blow
Room → Lap/Chute
↓
Lap/Chute → Carding
→ Sliver (Carded)
↓
Carded Sliver → 1st Drawing frame →
Drawing Sliver
↓
Drawing Sliver
→ 2nd Drawing frame → Drawing Sliver
↓
Drawing Sliver
→ Rotor Spinning → Rotor Yarn
2.2
Rotor spun technique:
In open-end spinning, this flow
of fibers is interrupted, the fiber strand being opened into individual fibers
at a predetermined position, usually by means of an opening roller, followed by
airborne fiber transport. This interruption or break in the fiber flow is physically
achieved by increasing fiber speed locally to very high levels (up to 100 m/s),
so that according to the equation of continuity, the number of fibers in the
cross section drops to such low values that the fibers lose contact with each
other.
This enables twist to be imparted
merely by rotation of the yarn end, which in turn leads to a significantly
higher potential rotation speed. A constant stream of separated, individual
fibers is allowed to flow to a rotating yarn end. The brush-like, open yarn end
grasps the fibers brought into contact with it and continuously binds them into
a yarn with the aid of the continual rolling movement.
2.2.1
Yarn properties:
Generally rotor spun yarns have following properties:
ü
More even
ü
Higher strength uniformity
ü
Higher production rate
ü
Fewer processes
ü
Lower cost
ü
Fewer imperfections
ü
Harsher hand (feel)
ü
Not as strong
ü
Limited counts-coarser yarns
ü
“Z” twist only
2.3
Advantages and disadvantages of rotor spun yarn:
Following are the advantages and
drawbacks of rotor spun yarn:
ü The
twist in the yarn being determined by the ratio of the rotational speed of the
rotor and the linear speed of the yarn.
ü The
production rates of rotor spinning is 6- 8 times
higher than that of ring spinning and as the machines are fed
directly by sliver and yarn is wound
onto packages ready for use in fabric formation.
ü The
yarn is a lot cheaper to produce.
ü Rotor
spun yarns are more even, somewhat weaker and have a harsher feel than ring
spun yarns.
ü Rotor
spun yarns are mainly produced in the medium count (30 Ne, 20 Tex) to coarse
count (10 Ne, 60 Tex) range.
ü The
use of this system has two basic advantages. It is fed by sliver, not as with
the ring frame by roving, and so eliminates the speed frame from the process
line. It can also be modified to remove any remaining trash to improve yarn
quality.
ü Open-end
yarns tend to be more uniform, lower in strength, more extensible, bulkier,
more abrasion resistant and more absorbent.
ü Open-end
spinning operates at a rate up to five times that of ring spinning and can be
effectively used for cotton, polyester- cotton blends, as well as other short
and medium staple systems.
2.4
End uses of rotor spun yarns:
Open end yarns produce different characteristics in the end
product. These yarns may be used to advantage in fabrics where uniformity and a
smoother surface are of prime importance. Open end yarns are used in pile
fabrics, apparel, household, industrial and technical applications. Uses
include heavy weight satin and poplins, corduroy, velveteen, rain wear, denims,
drills, sheets, pillow cases, bed spreads, printed fabrics, curtains, window
blinds, upholstery, cleaning cloths, dress goods, underwear, rugs, carpet,
blankets, terry towel and diapers.
3
Vortex spun yarn:
Vortex spinning technology was introduced by Murata Machinery
Ltd in Japan in 1997. This technology is best explained as a development of air
jet spinning, making use of air jets for yarn twisting. The main feature of
Murata vortex spinning (MVS) is its ability to produce yarn at 400 m/min, which
is almost 20 times greater than ring spinning frame production. Other
advantages include low maintenance costs, a fully automated piecing system and
elimination of roving frame. The yarn and the fabric properties of MVS yarn are
claimed by the manufacturer to be comparable to those of ring spun yarn.
3.1
Manufacturing principle:
The sliver is fed to a 4-over-4 (or a four-pair) drafting
unit. As the fibers come out of the front rollers, they are sucked into the
spiral-shaped opening of the air jet nozzle. The nozzle provides a swirling air
current which twists the fibers. A guide needle within the nozzle controls the
movement of the fibers towards a hollow spindle. After the fibers have passed
through the nozzle, they twine over the hollow spindle. The leading ends of the
fiber bundle are drawn into the hollow spindle by the fibers of the preceding
portion of the fiber bundle being twisted into a spun yarn. The finished yarn
is then wound onto a package.
3.2
Vortex spun yarn properties:
·
More
ring-like structure
·
Lower
hairiness
·
Dyes
darker
·
Good
handling properties
·
Highest
productivity
·
More
torque
·
More
waste in spinning
·
Limited
count range
3.3
Applications:
The application of vortex spun yarns depends strongly on
their quality and particular characteristics. Their initial application in
woven fabrics was focused on cotton-rich sheeting. MVS yarns broaden this focus
to 100% cotton sheeting as well. Other woven end-uses are twill fabrics and
fleece fabrics production.
Application to knitted fabrics is spread over interlock and
pique knits as well as jersey outerwear. MVS yarns are good for fleece-wear and
single knit jersey as they show less pilling and fuzz formation.
The specific structure of MVS yarns leads to a noticeable
decrease of the pilling problem. The result is that MVS yarns produce fabrics
suitable for suits, shirts, upholstery and curtains. The low shrinkage levels
make the yarns very appropriate for linings and beltings.
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