Technology of Denim
Production: Part – I
(Yarn Manufacturing Techniques
By: Supriya Pal
The term "Denim" has developed from the city of Nimes in France denim was
produced for the first time. In the nineteenth century heavy cotton fabrics were
produced in the Rhone Valley region of France. These fabrics were known as
“tissue de Nimes” and “Blue de Genes”. The term “denim” and “jeans” derive from
The classical denim is a heavy fabric made from 100% cotton and woven from
coarse indigo dyed warp and grey undyed weft yarn. The traditional denim is hardwearing, high density fabrics with a high mass per unit area and a 3/1 or 2/1- twill
Denim is available in attractive indigo blue shades and is made for a variety of
applications and in a wide range of qualities and shades. Classical denim is made
from 100% cotton dyed with Indigo blue shades. Besides classic indigo blue, denim
is also dyed in other fashion shades and colors, the most popular being black
denim. Denim is comfortable, fashionable, affordable and durable and popular in all the age group. Denim
is available in different weight ranges from 6 – 16 oz/sq yd which is categories as light denim 10-12 oz/sq
yd., heavy denim 14-16 oz/sq. yd.
In order to produce good quality denim, the yarn quality used for denim
production should be optimal. In rope and slasher dyeing machine the
passage of yarn is very long. Hence it is necessary to control the lapping of
yarn in the passage of yarn, otherwise bands of high and low densities will
be formed in the yarn, which ultimately cause shade variation in the fabric.
This leads huge loss of fabric. Therefore the TM of the yarn is to be
appropriate to avoid any snarling of yarn during running through the
passage. The yarn should be free of weak place, to avoid any breakages
during dyeing. Long slub, thick and thin
places in the yarn may leads to
prominent fabric defects in the fabric, as
denim is a contrast fabric made of indigo
blue warp and grey weft yarn. The weft
yarn hairiness should be low, otherwise
high yarn hairiness and major variation in yarn hairiness shown weft
bands which is a major fabric defects. Higher yarn neps may also
cause serious fabric defects.
The quality criteria of carded OE or ring spun yarns used for denim
production are as follows:
x Minimum staple length: 2.7cm
x Short fibers proportion (less than 12 mm long) should be under
x Micronaire value should be 4.0 - 4.5,
x Twist factor : 4.5 to 5.0, for warp yarns, 4.2 for filling yarn,
x Low yarn hairiness, low neppiness
x Good yarn strength and uniformity.
In the early 1990s, the majority of yarns used in denim production were OE yarns. However, recently,
there is a strong demand of using more carded ring spun yarns in both warp and weft, which gives the
fabric a softer handle.
Warp yarns for bottom weight jeans typically range from Ne 4.0 to Ne 12.5/1 or as per requirement of
finished denim fabric. Finer yarns are used for lighter weight jeans, vests, dresses, and skirts and the
yarns range may be from Ne 12.5 to Ne 30.0.
Production of the yarn for denim
The initial stage of denim production starts from opening and blending of cotton fibers. The cotton fibers
from the bale being separated into small tufts and a blend of cotton fibers are made in opening machines.
Cotton is transferred by air stream through the opening and blending machines and fed to the Cards.
The raw material for Denim yarn is mostly cotton, although lycra core yarn in warp and rayon, polyester or
polypropylene in various proportions are also used in weft. The type and quality of yarn used in denim
varies from country to country and regions to regions. Due to this variation in yarn type, it is very difficult
to spinners to envisage a standard line to fulfill all the requirement of yarn quality. Manufacturers of
opening, blending and cleaning machinery should offer a blowroom line which can meet the requirements
of all the customers.
The variations in colour of cotton from bale-to-bale and region to region may cause a serious shade
variation in denim fabric from lot to lot. Hence blending plays a very important role to minimize the lot to
lot shade variations in denim finished fabric.
The traditional blowroom is commonly practice with pre-open the bales and make a stack mixing or bin
blending. It is then fed to a hopper blending opener and into mixing chamber manually. However the
modern blowroom line consists of opening the bales by automatic bale plucking machine. It removes
small tufts of cotton fibers from a numbers of bales in a line and pneumatically feeds to a blending
However both the systems have their own advantages and disadvantages. The hopper blending method,
the manual opening of cotton fibers from the bale having the advantage of easy removal of fibrous
material, foreign materials such as plastic material, jute, polypropylene, stones, hard metal pieces etc.
However this has the disadvantages of low productivity and even lack of optimum blending. The manual
bale opening process depends more on the performance and efficacy of the worker, and has more
variation in the tuft size fed to the bale opener. Whereas the automatic bale opening offers a uniform tuft
size cotton fibers fed to the subsequent blending and cleaning machines.
Opening is the first process in any blowroom line which have the aim to achieve a high degree of
openness of material with gentle fiber treatment. The loss of fiber should be as less as possible. Opening
can be achieve in opening to flocks in the blowing room and in the opening to fibers in the card and OE
Incorporation of fourth or fifth cleaning step in a blowroom line contributes high fiber losses, but their
contribution on the over-all cleaning efficiency is marginal and quality reduction is considerably higher.
The modern cleaners offer intensive but gentle cleaning. Most of the modern blowroom lines followed
short cleaning lines with only two or three cleaning points. One pre-cleaner and one or two fine- cleaners
per line are incorporated in modern blowroom line. Trützschler CVT-4 Cleaner is incorporated with 3 to 4
beaters in series which gives cleaning in the same machine rather than 2 or 4 machines in tandem in line.
For rotor spinning de-dusting is very important. Cleanliness of the sliver
is an important parameter for denim yarn produced from open end
spinning system. Hence dust removal from the cotton fibers is an issue in
any modern opening and cleaning lines. In order to remove the very fine
micro dust particles from the cotton fibers, it is the usual practice of a
modern blowroom line to place a dust removal machine at the end of the
opening and cleaning line just before the chute feed or lap former,
because better the fiber opening better the de-dusting. De-dusting of
cotton fibers normally carried out by air suctioning, either between the
machines, by dust cages, dust extractors, or within the machine by
normal air separation.
De-dusting normally starts with pre-cleaning of cotton fiber. However a
separate machine like DUSTEX of TRUTZSCHLER is very effective for
de-dusting. ҏ Rieter de-dusting in machines like unimix, ERM, stationary de-dusting condensers can be
used for this purpose. Fine openers like ERM, CVT cleaners also remove the dust.
Blowroom machines have to fulfill various functions, such as to supply small fiber tufts, clean fiber tufts,
homogeneously blended tufts if more than one variety of fiber is used to carding machine without
increasing fiber rupture, fiber neps, and broken seed particles and without removing more good fibers. In
order to achieve these requirements, the blowroom may vary in concept and in design. There are no
universal machines for a blowroom line. Basically, the sequence of different machines arranged in series
in any blowroom line depends among many other things, such as: the type of raw material; the
characteristics of the raw material; waste content; dirt content; material throughput; the number of
different origins of the material in a given blend.
Basically, the above mentioned functions may be achieved in different processes in the blowroom:
1. Pre- opening
2. Pre- cleaning
3. Mixing or blending
4. Fine opening
Typical blowroom line is illustrated in Fig. 1.
An efficient preopening of cotton fiber results in smaller tuft sizes and offers a large surface area for easy
and efficient removal of trash particles by the fine openers. The trend in modern spinning mills is to
replace old manual bale opener to automatic bale opener, which gives smaller tuft size, better opening
and cleaning efficiency. In the latest automatic bale opening machines, the tuft size can be as small as 50
to 100 grams without rupturing the fibers. The opening roller speed is around 1500 to 1800 rpm. The
automatic bale opener helps to maintain the homogeneity of the long term blending and the cotton is
opened gently without recycling as it is done in manual bale openers. Maximum number of take-off points
is available per unit time by setting the machine parameters.
Rieter Automatic Bale Opener (UNIfloc A 11)
Rieter UNIfloc A 11 uses single plucking / take-off roller, which along with narrow grid results in small tufts
size (Fig. 2). . It enables up to 130 bales arranged per side with four components (different bale types)
per blend to be processed. The layout length may be up to of 50 m. The UNIfloc A 11 machine can
process one or two blends simultaneously. The production rate is up to 1400 kg/h.
Trützschler Automatic Bale Opener (BLENDOMAT BO-A)
consist of two plucking rollers which
rotate in opposite direction. According to
the direction of travel of the machine at
any given time only one plucking roller is
working while other is raised. The
plucking roller penetrates into the bale
surface and strips off the tufts. At that
time three supporting rollers give a firm
grip over the bales. This ensures gentle
fiber removal and gives good opening
Crosrol Automatic Bale Opener (ABO)
The Crosrol Automatic Bale Opener (ABO) having the facility to operate up to four different bale groups of
different heights together (Fig. 4). The production rates is up to 1500 kg per hour. The machines offers
virtually unrestricted track length. The users are able to lay down as many as 200 bales in four groups on
each side of the machine. The twin contra-rotating rollers and a specially developed grille spacing results
in small tufts to be plucked.
Rieter blowroom Line
The Rieter blowroom line typically consists of
automatic bale opener UNIfloc A 11, intensive precleaner UNIclean B 11, homogeneous mixer/blender
UNImix B 70 and gentle fine cleaner UNIflex B 60. For
coarse yarn of rotor spinning, maximum production is
about 220 kg/h.
Rieter UNIfloc offers gentle opening of the cotton tufts
with large surfaces which provide the basis for
homogeneous, intimate blending. The UNIclean
provide gentle and efficient cleaning of this tuft surface
and remove large trash particles. The VARIOset
device in UNIclean and CLEANfeed ensures optimum
cleaning efficiency, quality, flexibility and economy by
adjusting the trash removal selectively at the push of a
The UNImix is a unique 3-point blending process
which ensures very intensive blending and uniform
yarn quality. The fine cleaning stage consists of several CLEANfeed units which ensures gently cleaning
and de-dusting of raw material.
Trutzschler Blowroom Line for the production of denim yarn
Trutzschler offers compact blowroom line for denim yarn production which consists of:
Automatic bale opener,
High Capacity Condenser LVSA , Pre mixer BOA,
Double roll cleaner AXI-FLO AFC,
Station for separating Foreign Matter SEcuromat,
Two Way distribution,
High Capacity Condenser LVSA, Cleaner Clenomat CVT4,
Dedusting Machine Dustex DX,
Pre-cleaning machines are normally preceded by the bale-opening machines that produce small flocks
with large surface areas. As the bale-opening machines are not fitted with cleaning devices, they cannot
clean the surfaces of the flocks. Even if the bale-opening machines equipped with cleaning devices, they
can remove only a fraction of the impurities owing to the high material throughput.
Pre-cleaning should be gentle as possible without creating any fiber damage and more nep generation.
Seeds and bigger trash particles should not be broken as removing finer trash particles is difficult. Proper
preopening and pre-cleaning ensures efficient trash removal by fine openers. Dust removal should be
started at this stage of blowroom process. Rieter's Uniclean B11 and Trutzschler's Axiflow or Maxiflow are
some of the machines which ensures efficient pre-cleaning.
Rieter offers unique "VARIOSET" through which selective trash removal is possible. Waste amount can
be changed in a range of 1:10.
The opening and cleaning of cotton fibers depends on several parameters such as distance between
beater and feed roller, speed of beater and grid bars setting. The Rieter VarioSet System adjusts several
parameters during running of the machine. The cleaning intensity (0.0 to 1.0) and relative quantity of
waste (1 to 10) can be entered to the VarioSet. These two parameters adjust the beater speed and grid
bars setting on Rieter UNIclean B12 cleaner to get the required level of waste extracted. In UNIflex B 60
cleaner fiber length, relative amount of waste (1 to 10) and cleaning intensity (0.0 to 1.0) are entered.
Uneven mixing of different cottons fiber may cause barre or streakiness in denim fabric. Hence adequate
mixing / blending of cotton fiber is very important. More intensive mixing is required if the cotton of
different parameters such as fineness, color and staple length are process at a time. Trutzschler's tandem
mixing concept guarantees a maximum homogeneous mixing and it is very useful if the mixing
requirement is very high (Fig.6).
Several machinery manufacturer offers multiple mixer which gives a good long-term blending. The multimixer consists of several (from six to eight) chute chambers into which the material is filled from above.
The material is then removed from all chutes simultaneously.
Trutzschler multi mixer can have 6 or 10 trunks (Fig. 7). All the trunks are filled with material from above.
The material is then removed from all trunk through the conveyor belt. Trutzschler also offer Multi-mixer
MCM 6 with cleaner CLEANOMAT CXL Machines.
Rieter UNImix blending machine
Rieter UNImix is made up of three parts: a storage section, an intermediate chamber, and a delivery
section. Flocks are fed into J- shaped chutes (2) (Fig. 8 & 9) which is arranged one behind the other in
the storage section. The conveyor belt (3) then carry the stock through the chamber to the take-off unit.
The material columns are thus converted from the vertical into the horizontal.
Fine cleaners may have single opening rollers or multiple opening rollers depending upon the amount and
type of trash in the cotton. If single opening roller cleaners are used, then the number of fine cleaning
points can be either one or two. Trutzschler offers single opening roller machine CVT1 for roller ginned
cotton. In case of saw ginned cotton CVT3 or CVT4 machines with 3 or 4 opening rollers can be used.
The CVT1, CVT3, CVT4 etc consists of opening roller, deflector blades, mote knives and suction hood
which act as cleaning points (Fig. 10). The trash particles which are removed due to centrifugal forces are
separated at the mote knives and then suck away by the suction.
Trutzschler first introduced usage of multiple beaters/cleaners in tandem on the same machine. The
machine has both clamped and unclamped material feeding system to the beaters. At the first beater the
material feeding is clamped through the feed rollers which give intensive beating. In the subsequent
beaters the material is transferred in unclamped manner which gives gentle cleaning. The gradual
increase in beater speed, fineness of clothing and angle of clothing teeth from first to last beater offers
progressive cleaning of the material.
The cards is plays an important role for the quality of denim yarns and for the efficiency of the production.
The carding quality is influence in the area of cylinder, flats and stationary carding segments. Several
factors, such as cylinder speed, clothing fineness, distances between cylinder and flats, distances
between cylinder and carding segments influence the quality of carding. The yarn quality is directly
related to the quality of card sliver.
Rieter card C60 and Trutzschler TC 07 are equipped with unidirectional feed system which results in
gentle fiber treatment because fiber feed and licker-in rotation is in the same direction. Both the above
cards are equipped with multiple licker-in for better cleaning of the feed material.
Rieter C 60 Card has 50% more working width (from 1 m to 1.5 m) as compare to their previous model C
51. Trutzschler TC 07 with longest carding section (2.82 m) ensures more intensive the carding and
higher production. The pre-carding area ensures better the pre-opening and optimal fiber web preparation
for better carding.
Pre-carding zone of Rieter C 60 Card extract impurities and the suctions hoods transferred these to
centralized waste chamber. The post-carding zone of Rieter C 60 Card has 2 carding elements.
Trutzschler TC 07 card has pre-carding zone with 3 carding elements and 3 cleaning elements. The postcarding area of this card has 6 carding segments with 3 cleaning elements.
Rieter Integrated Grinding System (IGS-Classic for cylinder wire grinding and IGS-Top for flat wire
grinding) offers better quality in terms of reduction in neps and trash of card sliver.
Rieter medium and long term auto leveller on C 60 card control card sliver count variations, count CV%
and unevenness. The Integral Feed Tray SENSOFEED of Trutzschler TC 07 card constantly scans the
thickness of the tuft web and adjusts the speed of the feed roll as required. In the long-term auto leveling
system the sliver mass is measured by the sensor in the card sliver trumpet and the speed of the feed
roller is adjusted accordingly.
Now-a-days, the cards are integrated with 3-over-3 drafting which are able to reduce one draw frame
passage particularly for rotor spinning. Trutzschler offers Integrated Draw Frame IDF with Card TC 07. It
has 3 over 3 two-zone drafting system with a draft of 3-fold. The delivery speeds is 500 m/min
For OE denim yarn production, the number of drawframe passages is most important. For open end
spinning line two drawframe passage is the standard. Although new spinning mills in USA and Europe
use only one auto-leveller draw frame. However, it is believed that two draw frame passage helps to
achieved better results in dyeing, weaving etc. Specifications of different makes of Draw frame is given in
Table 1: Specifications of different makes of Draw frame
LR SB 851
GmbH & Co.
3.05 to 11.6
4.5 to 11.6
4 to 14
4 to 11
Single or twin
Single or twin
4 to 11.6
Single or twin
Single or twin
No of deliveries
Riter offers RSB-D 40 autoleveler drawframe and the SB-D 40 drawframe in which quality can be
significantly improved (Fig. 11). The delivery speeds of up to 1100 m/min. Superior yarn regularity (Uster
CV%) can be achieve with this drawframe. The drawframe has self-adjusting auto leveling function
AUTOset, precise fiber guidance in the drafting system. The novel suction system with periodically lifting
cleaning lips on the top rollers enhanced the yarn cleanliness.
In the case of processing carded cotton in ring spinning, the RSB-D 40 delivery speeds of 850 m/min are
achieved in mill operations. However in rotor spinning even higher delivery speeds can be achieved.
AUTO DRAFT of Trutzschler TD 03 draw frame estimates the values of the break draft merely in one
minute. It takes into consideration several important parameters such as, fiber-fiber friction, fiber to metal
friction, etc, while calculating the break draft. Trutzschler draw frame TD03 can be equipped with round or
rectangular cans. Rectangular cans are particularly efficient.
Rotor Spinning Machine
Modern Open-end rotor spinning are high productive, cost efficient and consume less energy are very
successful in denim yarn production. The rotor speed in latest machine exceeds 150,000 rpm and the
take-up speed 300 m/min. Package weights up-to 5 to 6 kg can be made in latest machine which
subsequently helpful to increase the productivity in subsequent process in denim production.
Predetermined length of yarns are wound on to the packages with great accuracy which reduce the
wastage in ball warping in case of rope dyeing and direct warping in case of slasher rope dyeing in denim
process. The anti-patterning systems, electronic yarn monitoring system, foreign fiber separation system
reduce the fabric defects and end breakages in denim weaving. The fancy yarn preparation system
incorporated in latest open-end spinning machine offers variety of fashionable denim production, which
gives a value added products.
Open-End yarn Denim Fabric
Rieter’s rotor spinning machine R40 is the result of the co-operation between Suessen and Rieter. The
R40 rotor spinning machine can spun yarns in count of Ne 3-60 / 200-10 tex. The newest R 40 offers
maximum productivity with a maximum length of up to 500 spinning positions per machine, up to 350
m/min delivery, rotor speed of up to 160 000 rpm, up to 4 robots (Fig. 13). With the maximum machine
length, the delivery speeds of up to 270 m/min can be achieved. However with fewer spinning positions,
350 m/min can be obtained. Slub yarn, Multicount and Multitwist yarn can be made, as an additional
feature, at full machine length.
Slub denim fabric is a current fashions trend. Hence the demand for slub yarn is also very high. By using
a special opening roller, an effect in the yarn can be created. The R 40 can be equipped with a Caipo
device for slub yarn, multi-count and multi-twist.
Fig. 13: Rieter rotor spinning machine
Rieter BT rotor spinning machine is equipped with an attachment of slub yarn production from Caipo
Automazione, Italy. The motorised variable sliver feeding system can produce slub yarn (coarse and fine),
multicount with twist variation, multitwist etc.
The Schlafhorst Autocoro 480 offers higher productivity with up to 480 spinning positions and the
Corobox SE12. The Twin Disc bearing of the Corobox SE 12 offers high rotor speeds of 150,000 rpm at
480 spinning positions. Coarse yarns are spun at take-up speeds of up to 300 m/min ensures highest
productivity. The Autocoro 480 is equipped with up to 4 Coromat unit per machine. The Corobox SE12- a
universal SpinBox for all types of fibres and yarns, offers maximum productivity and optimum quality.
Yarns counts from Ne 4 to Ne 60 can be made with a draft range of 20 to 450 fold. The Corobox SE12
equipped with individual motor controlled SDSI Single Drive Sliver Intake which guarantee an exactly
defined sliver intake. Fancy yarns can be produced in Autocoro 480.
Schlafhorst Autocoro 480
The Corobox SE 12
The Belcoro spinning components used in spinbox and offers an outstanding yarn quality and ensures
long service life and high, reproducible yarn quality. The Autocoro 480 is equipped with the new Corolab
XF which ensures optimum yarn clearing with 100% foreign material detection. The new Corolab XF
which not only ensures good yarn quality, but also 100% digitally controlled piecing.
Modern ring-spinning and open-end spinning machines can be incorporated with certain attachment that
can make predetermined yarn effects. These yarn effects are multicounty, slubs of different lengths and
different spacing between slubs.
The rotor machine offers tremendous flexibility in term of fancy yarn production. Various devices can be
included in the rotor machine to produce fancy/slub yarn. Schlafhorst Autocoro 480 rotor spinning
machine is incorporated with fancy yarn device, known as ‘FancyNation’. A small stepper motor is used to
produce fancy/slub effect through the Single Drive Sliver Intake (SDSI). It ensures a precisely metered
fiber feed at every spinning position. The fancy yarn software ‘FancyPilot’ forms the basis of Fancynation
. It can produce and simulate effects of different fancy yarn in fabric stage without actual production of the
yarn. The software tool FancyPilot generates the production data for the Autocoro 480 directly from the
design. It can simply transfer the data to the Informator-and fancy yarn production may starts
The fancy yarn effect in 3D simulations of woven and knitted fabrics can be seen. The digital Corolab
technology monitors the fancy yarns reliably at every spinning position. Effects in existing yarns can also
be reproduced quickly and simply. Fancynation analyses the effect style and generates a data record for
the Autocoro 480. Fancynation acts as the “memory” of the fancy yarn production. It can be access all
spinning and piecing settings for fancy yarns already produced in a database which enables to
reproduce any yarn quickly at any time.
Ring spinning is the original former standard method of denim fabric production. In the early 1970s, denim
is normally made with ring yarn, rather than open-end yarn. The ring denim then gradually replaced by
OE denim for reasons of productivity.
With the course of popularity of vintage-look blue jeans and retro denim wave, ring denim was
reintroduced. The soft feel and unique surface characteristics of Ring denim, it gradually became
popular. The retro look of ring denim can again be increased through different finishing and washing. In
the world of ring denim, some other type of denims is also getting very popular. One of which is stretch
Saurer offers the denim ring spinning machines and components especially developed for denim
Zinser offers different spinning machines for denim production with a new potential for cost reductions as
well as increased productivity.
Fig. 14: Zinser 670 BigPac coarse yarn
roving frame, ideal for denim applications
Zinser 670 BigPac roving frame was specially
developed for coarse yarn production (Fig. 14).
The bobbin size of 20 by 7 inches increases the
productivity and the bobbins weight of up to 4 kg
can be made which drastically reduced the
operating and set-up times. The longer running times of the bobbin at the roving frame and at the ring
spinning machine reduce the number of bobbin changes. This is very beneficial during producing coarse
yarns, particularly in the field of denim.
Zinser 351-cotton ring spinning machine
Zinser 351, which is ideal for denim applications, are equipped with ServoDraft (electronic drafting system
drive), New CoWeMat (automatic doffer) and OptiSuction (electronic suction low pressure regulation).
Cop weights of up to 200 grams are possible in this machines for economic production of denim yarns.
Zinser offers the fancy yarn system FancyDraft which produced fancy ring yarns in Zinser 351/ 451 ring
spinning machine from both short-staple and long-staple fibers. With the electronically controlled drafting
system drive ServoDraft equipped in the Zinser 351, FancyDraft can produce different types of fancy
yarns. The draft as well as the twist can be varied in FancyDraft in a controlled manner. Different
parameter can be set via the new graphic machine user interface EasySpin. Fancy effects with different
thickness, length and twist are incorporated in the yarn. Slubs of different length, diameter can be
produced with this attachment. The twist can also be varied for multitwist yarns production.
Multi-Count Effect in Denim
'Count' is the thickness of the yarn used in fabric. Multicount fabric is built from yarns of varying thickness
or variation in count along the length which gives a unique luxurious look to denim fabric. However the
washing gives superior on multicount.
Multi-count yarn is becoming very popular in denim which is produced by a special device. The multicount effect is made by having controlled count changes in length (as short as 2 meters) while
maintaining a constant twist level.
Multicount yarn production follows the basic principles of slub yarns production. In the production of
multicount the speed of the production roller are varied by means of additional servomotors to adapt the
twist coefficient to each type of count combined along the same yarn.
A mass variation in the yarn is made by varying the drafts (main draft). The main draft is reduced to
create fancy effects in the yarn. In order to achieve this, the speed of the middle and the rear bottom
rollers is temporarily increased.
The multi-twist effect in yarn is produced by applying different twist coefficients to the same yarn count.
The multi-twist yarn is produced by means of the controlled, accurate acceleration of the production roller.
These variations in twist create variations in the yarn's dye intake which offers a special fabric
Fig. 15: Multi-twist denim
Twist variations in the yarn is incorporated by varying the delivery speed to the spinning machine. In order
to obtain the twist variation in the yarn, the ratio of the front bottom roller speed compared to the constant
spinning speed (SynchroDrive) is varied whereas the draft remains constant.
Fig. 16: Multi-twist principle
AMSLER-TEX AG is a Swiss company offering equipments and associated software for fancy and elastic
yarn production. AMSLER control devices can be attached with almost all types of spinning machines. It
is a microprocessor-controlled servomotor system, which controls the spinning process to produce the
desire effect in the yarn.
The Amsler Slub yarn devices can produce ground slub and multi-twist effect in Open-End spinning.
Whereas in case of ring spinning, it may produce ground slub, multi-count and multi-twist-effect.
Amsler slub yarn can be produced on open end or on a ring spinning. Normally Amsler slub effect in
denim is made on open end. This is an attachment to open end spinning that allows slub and multi-twist
effects in the yarn. In ring spinning, the slub yarn is made by varying the speed of the feed and
intermediate roller and at constant speed the production roller.
In ring spinning machine, a servo drive system is connected to the back and middle roller via a special
gear box. The servo motor starts only at the time of slub formation and additional speed is given to the
drafting system, which disturb the normal yarn formation.
In case of open end spinning, the slub yarn is produced in the same principle which is explained with the
Fig. 17: Principle of slub production in open end spinning
Stretch denim is a full fashion fabric and wildly popular in ladies and kids garments due to its stretch-to-fit
character. The stretchable character of stretch denim fit closely with the body rather than restricting the
movement. Due to longitudinal elasticity of stretch denim, it is more comfortable when sitting or bending
down, it fits well due to its cross elasticity. The stretch denim fabric is made with Spandex core spun yarn.
Core-spun yarns can also be produced in ring spinning, open-end and air-jet spinning machines. The
core spandex filament yarn is fed through the rotor shaft of open-end spinning or the spindle of the air-jet
frame, and the cotton fiber wraps around the spandex filament to produce the core spun yarn. The
properties of this yarn is almost similar to the ring core-spun yarns, however the open-end and air-jet
core-spun yarns have less knots and splices as compared to ring core-spun yarns.
Spandex Core spun Denim
Conventional Core spinning attachment in Ring frame
In ring spinning machines, Core-spun yarns can be produced by incorporating a spandex/ lycra
filament at the back of the front drafting roll of the machine (Fig. 18). The spandex core ring spun yarn
is produced when the drafted cotton fibers twist around the spandex filament yarn.
Fig. 18a: Conventional Core spinning attachment in Ring frame
Elastic core yarns can be produced in ring spinning which consist of an elastic core around which staple
fibers are wound (Fig. 18a).
Fig.18b: Elastic core yarn
The elastic filament is pre-drafted approx. 2.5- to 4-fold before being inserted to the spinning zone
ahead of the front top rollers. This process has the advantage that the sensitive filament is completely
wrapped by staple fibers (Fig.18b).
Twofold elastic SiroSpun / Elastic spin-twisted yarn
Elastic spin-twisted yarns can be produced by combining the CoreSpun and SiroSpun process, which
produce directly weavable, twofold elastic SiroSpun yarn on the ring spinning machine. In the production
elastic spin-twisted yarns, two staple fiber roving are drafted in parallel and the elastic filament is then
introduced in the front pair of drafting rollers (Fig. 19).
Fig. 19: Elastic spin-twisted yarns
Zinser short and long staple ring spinning machines can be equipped with CoreSpun and SiroSpun units.
Elastic OE rotor yarns
Schlafhorst BD 340 filea rotor machine can produce elastic core spun yarn. The elastane core filament is
fed through the hollow rotor axis which is covered by the rotor yarn produced in the rotor from staple fiber
material (Fig. 20). Twist is not given in the core filament yarn, thus elasticity of the filament is maintained.
Fig.20: Elastic OE Rotor yarn
Rotor core yarn can also be produced on the Rieter BT 924 rotor spinning machine. A core filament
(elastic or non-elastic) is supplied through a special device via, a guide tube. The core filament yarn is
covered by the staple fiber yarn.
Fig. 21: Core spun yarn production by rotor spinning
Elastic covered twist yarns
The ElastoTwister by Saurer Hamel / Volkmann can produce elastic covered twist yarns in which the
elastic core filament yarn is covered by the twisted feed material. The cover yarn, produced without a
balloon, has no twisted core yarn (Fig. 22).
Fig. 22:Elastic covered twist yarns
Elastic ply yarns
Elastic ply yarns can be produced in two-for-one twisting machine. The elastic filament yarn and the
individual yarns and are placed on a doubling bobbin and are twisted into one another in the twisting pot
(Fig. 23). This twisting process offers high productivity.
Fig. 23:Elastic ply yarns