Part - 02

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IntroductionFriction (DREF) spinning system is an Open-end spinning

system.Along with the frictional forces in the spinning zone the yarn

formation takes place.The DREF system is used to produce yarns with high delivery

rate about 300mpm.It produce a highly uniform yarn from diverse stock including

short or difficult to handle at high production rates and low labor and energy expenses.

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Principal of friction spinning

Fibers are delivered onto the drum surface, which transports and stacks the fibers to the fiber bundle rotating between two surfaces moving in opposite directions.

The fibers wrap around the bundle surface.wrapped fiber bundle (yarn tail) is tugged by the yarn delivery

roll.Therefore twists by fiber arrangement are generated.Due to separate yarn winding and method of twist insertion, it

has capability to go for high production rate.

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Principal of friction spinning system Cont…

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Type of DREF spinning

DREF-1DREF-2DREF-3DREF-5DREF-2000DREF-3000

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DREF-1

DREF-1 friction spinning system was developed in 1973 by Dr.Fehrer.A.G. of Austria.

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DREF-1 Cont…

The fibers were opened with an opening roller and allowed to fall on a single perforated cylindrical drum slot

The rotation of the drum impart twist to fiber assemblyThe ratio of perforated drum to yarn surface is very large,

hence the drum speed can be kept relatively low.Due to the absence of positive control over the fibers

assembly, slippage occurred between the fiber assembly and perforated roller, which reduced twist efficiency

Hence this development could not be commercialized

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DREF-2DREF-2 was exhibited in the year 1975 at ITMA exhibition.It operates on the basis of mechanical/aerodynamic spinning

system with an internal suction and same direction of drums rotation.

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DREF-2 Cont…Drafted slivers are opened into individual fibers by a rotating

carding drum covered with saw tooth type wire clothing.The individualized fibers are stripped off from the carding

drum by centrifugal force supported by an air stream from the blower.

Fibers are transported into the nip of two perforated friction drums where they are held by suction helping in the removal of dust and dirt thereby contributing to production of cleaner yarn.

The fibers are sub-sequentially twisted by mechanical friction on the surface of the drums.

The low yarn strength and the requirement of more number of fibers in yarn cross-section (minimum 80-100 fibers) were restricted the DREF-2 spinning with coarser counts (0.3-6s Ne).

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Advantages of the core yarns produced using DREF-2 methodUniform breaking strength along the entire length and excellent

running properties for further processing (weaving and raschel knitting process).

Excellent yarn regularity.Good adhesion of the sheath fibers to the core. No rewinding required due to the direct provision of the cylindrical

bobbins to the weaving process in a weight range of 8 - 10 kg. Long, knot-free lengths. High weaving effectiveness, due to the eradication of thread breaks. High levels of area stability in the finished weave.Retention of a textile surface character.

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DREF-2 Application and Fields

Blankets for the home application range, hotels and military uses etc.

Interior decoration, wall coverings, draperies and filler yarn.Shoes, ropes and industrial cable manufacturing.Filler cartridge for liquid filtrationFor upholstery, table cloths, wall coverings, curtains, hand-

made carpets, bed coverings and other decorative fabrics.Heavy flame-retardant fabrics, conveyor belts, clutches and

brake linings, friction linings for automobile industry, packets and gaskets.

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DREF-3The DREF-3 machine is the next version of DREF-2 for

improving the yarn quality came to the market in the year 1981.

Yarns up to 18s Ne. can be spun through this system.

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DREF-3 Cont…

This is a core-sheath type spinning arrangement.The sheath fibers are attached to the core fibers by the false

twist generated by the rotating action of drums.Two drafting units are used in this system, one for the core

fibers and other for the sheath fibers.This system produces a variety of core-sheath type structures

and multi-component yarns, through selective combination and placement of different materials in core and sheath.

Delivery rate is about 300 m/min.

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DREF-3 Application and Fields

Backing fabrics for printing, belt inserts, electrical insulation, hoses, filter fabrics

Hot air filtration and wet filtration in food and sugar industries.

Clutch lining and brake lining for automotive industries.

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DREF-5

It was developed by Schalafhorst, Suessen and Fehrer.The range of count to be spun from this system is from 16’s to

40’s Ne.Production speed is up to 200m/min.This spinning system was not commercialized due to some

reasons.

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DREF-5 Cont…The individualized fibers from a single sliver are fed through a

fiber duct into the spinning nip at an angle to the yarn axis.They are stretched as far as possible, when fed into the nip.

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DREF-2000It is the latest development in friction spinning demonstrated

in ITMA 99.

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DREF-2000 Cont…

DREF-2000 employs a rotating carding drum for opening the slivers into single fibers and a specially designed system being used for sliver retention.

The fibers stripped off from front the carding drum by centrifugal force and carried into the nip of the two perforated spinning drums.

The fibers are subsequently twisted by mechanical friction on the surface of the drums.

Drums are rotates in the same direction.

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Advantages of DREF-2000 Insertion of twist in ‘S’ and ‘Z’ direction is possible without

mechanical alterations to the machine.Yarns up to 14.5s Ne can be produced at speeds of 250

m/min.Reduced yarn preparation costs due to high sliver weights

(card slivers).Dust extraction for secondary fibers.Low energy costs due to the use of only 1 fan for 12 spinning

heads.Feeding of all types of filaments, yarns and components as

yarn cores, in order to attain high yarn strength and production speeds, voluminous yarns and specific product characteristics.

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DREF-2000 Application and Fields Blankets for the homes, hotels, hospitals, camping, military uses,

plaids etc. Cleaning rags and mops from cotton waster and various waste-

blends Deco- and upholstery fabrics Outerwear and leisure-wear Filter cartridges for liquid filtration Secondary carpet backing for tufting carpets Canvas and tarpaulins for the military and civil sectors High-tenacity core yarn for ropes, transport and conveyor belts Asbestos substitutes for heavy protective clothing (protective

gloves, aprons etc) packing, gaskets, clutch and brake-linings, flame retardant fabrics etc.

Filter Yarns for the cable, shoe and carpet industries Carpet Yarns (Berber carpets, hand-woven and hand-knotted

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DREF-3000In the ITMA 2003, the first public appearance of the DREF

3000 was made.The yarn can be spun form 0.3Ne to 14.5Ne.

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Advantages of DREF-3000System Expansion of the scope of yarn and fiber utilization in

the coarse yarn count range Production of both ‘S’ and ‘Z’ yarns at any time without

mechanical alterations to the machine Reduced yarn preparation costs due to high sliver weights

(card slivers) Higher Bobbin weights through 200mm winding traverse.

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DREF-3000 Application and Fields High tenacity and FR protective clothing for civil & military

sector Fire blocker for the aviation and contract business range, cut

protection textiles (protective gloves, mail-bags, seat coverings)

Fiber composite materials for the aviation, automotive, machinery, and construction industry

Tarpaulins, transport and conveyor belts as well as all kinds of technical textiles

Filter fabrics for dry and wet filtration Upholstery fabrics for contact business range Knitting sector, elastomeric fabrics Outdoor textiles (eg chair and dock-chair covering)

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Yarn formation in Friction spinning system

The mechanism of yarn formation is quite complex. It consists of three distinct operations.

1. Feeding of fibers

2. Fibers integration

3. Twist insertion.

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Feeding of Fibers The individualized fibers are transported by air currents and

deposited in the spinning zone.There are two methods of fiber feed

1) Direct feed Fibers are fed directly onto the rotating fiber mass that

outer part of the yarn tail.

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Feeding of Fibers Cont…

2)Indirect feedFibers are first accumulated on the in-going roll and then

transferred to the yarn tail.

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Fibers IntegrationThe fibers through feed tube assembles onto a yarn core/tail

within the shear field, is provided by two rotating spinning drums and the yarn core is in between them.

The shear causes sheath fibers to wrap around the yarn core.The fiber orientation is highly dependent on the decelerating

fibers arriving at the assembly point through the turbulent flow.

The fibers in the friction drum have two probable methods for integration of incoming fibers to the sheath.

the fiber assembles completely on to perforated drum before their transfer to the rotating sheath.

fibers are laid directly on to rotating sheath.

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Twist insertion

The fibers are applied twist with more or less one at a time without cyclic differentials in tension in the twisting zone.

Therefore, fiber migration may not take place in friction spun yarns.

The mechanism of twist insertion for core type friction spinning and open end friction spinning are different.

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Twist insertion in core-type friction spinning

Core is made of a filament or a bundle of staple fibers is false twisted by the spinning drum.

The sheath fibers are deposited on the false twisted core surface and are wrapped helically over the core with varying helix angles.

It is believed that the false twist in the core gets removed once the yarn is emerged from the spinning drums, so that this yarn has virtually twist less core.

However, it is quite possible for some amount of false twist to remain in the fact that the sheath entraps it during yarn formation in the spinning zone.

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Twist insertion in Open end friction spinning

The fibers in the yarn are integrated as stacked cone.The fibers in the surface of the yarn found more compact and

good packing density than the axial fibers in the yarn. The Figure shown the arrangement of fibers in the DREF-3

yarn as stacked cone shape .

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Spinning Tension for DREF yarns

Friction spun yarns have less spinning tension during the yarn formation.

Due to less tension during the spinning the core component can be placed exactly at the centre of the yarn.

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Properties of Friction Spun Yarns

Friction spun yarns (DREF) yarns have bulky appearance (100-140% bulkier than the ring spun yarns)

The twist is not uniform and found with loopy yarn surface.Usually weak as compared to other yarns.The yarns possess only 60% of the tenacity of ring-spun yarns

and about 90% of rotor spun-yarns.The breaking elongation of ring, rotor and friction spun yarns

is equal.

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Properties of Friction Spun Yarns Cont…Depending on the type of fiber, the differences in strength of

these yarns differ in magnitude.100% polyester yarns-strength deficiency is 32%100% viscose yarns-it ranges from 0-25%

In polyester-cotton blend, DREF yarns perform better than their ring-spun counterparts.70/30% blend yarn-superior in strength by 25%

DREF yarns are inferior in terms of unevenness, imperfections, strength variability and hairiness.

The friction spun yarns are more hairy than the ring spun yarns

DREF yarns are most irregular in terms of twist and linear density while ring spun yarns are most even.

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Properties of Hybrid Yarns/DREF core yarns

If one yarn creates out of 2 or more single yarn components is called hybrid yarn.

Hybrid yarns are usedFor reinforced plastics

Properties of the yarn Core/Sheath structure with centric position of the reinforcing filament Zero twisted reinforced filament gives best strength result Definable fiber matrix proportion Protection of the reinforcing filament through the sheath fibers

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Hybrid Yarns/DREF core yarns Cont…For liquid filter cartridges

Yarn Properties Huddle fiber arrangement for best filter action High elongation values Long yarn length knotless Uniform yarn with high tensile strength

For heat proof woven and knitted fabricsYarn properties Flame resistance High temperature resistance High tear abrasion resistance Good wearing comfort Good care properties Skin friendly

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Hybrid Yarns/DREF core yarns Cont…For Secondary carpet backings

Yarn Properties Steady high tensile strength High uniformity of the yarn Long knotless length of the yarn Good non-rotating properties High chemical resistance Good thermal transfer Dust free product Electric insulation Good dimension stability for carpets

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Hybrid Yarns/DREF core yarns Cont…

For asbestos substitutesYarn properties High yarn volume Good temperature resistance High tensile strength Low elongation

Cut proof woven and knitted fabricsYarn properties High cut resistance Good wearing comfort High dimension stability

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Advantages of Friction spinning systemIt can spin yarn at very high twist insertion rates (ie.3,00,000

twist/min).The yarn tension is practically independent of speed and

hence very high production rates (up to 300 m/min) can be attainable.

Improved dirt particle retention and up to twice the filter service life.

Considerable reduced yarn production costs (up to 50%) due to lower yarn mass requirement, lower preparation costs, lower spinning costs and lower personnel expenses.

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Limitations of Friction spinning system

Low yarn strength and extremely poor fiber orientation made the friction spun yarns very weak.

The extent of disorientation and buckling of fibers are predominant with longer and finer fibers.

Friction spun yarns have higher snarling tendency. High air consumption leads to high power consumption. The twist variation from surface to core is quite high; this is

another reason for the low yarn strength. It is difficult to hold spinning conditions as constant. The spinning system is limited by drafting and fiber

transportation speeds.

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