Technology of denim production

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 und

Technology of Denim Production: Part –– I

(Yarn Manufacturing Techniques

ȱ

(YarnȱManufacturingȱTechniquesȱforȱDenim)ȱ

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

these designations

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

hard-wearing, high density fabrics with a high mass per unit area and a 3/1 or 2/1- twill

weave construction

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

Yarn Quality

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

40%,

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 machine

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 spinning machine

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

Dust Removal

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 Machinery

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:

Pre opening

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

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

(Fig 3)

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

pre-cleaner 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

button

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:

1 Automatic bale opener,

2 Fan TV500,

3 High Capacity Condenser LVSA , Pre mixer BOA,

4 Double roll cleaner AXI-FLO AFC,

5 Station for separating Foreign Matter SEcuromat,

6 Multi Mixer,

7 Two Way distribution,

8 High Capacity Condenser LVSA, Cleaner Clenomat CVT4,

9 Dedusting Machine Dustex DX,

Pre-cleaning

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

BLENDING:

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 mixer 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

multi-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 Cleaning

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

Cards

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 post-carding 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 (maximum)

Draw frames

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

Table 1: Specifications of different makes of Draw frame

Particular Machine Works Lakshmi

Lts

Rieter Machine

TOYOTA Textile Machinery

Trützschler GmbH & Co

Delivery speed

Drafting system 3-over-3 With pressure bar 4-over-3 With pressure bar 3-over-4 With pressure bar 3-over-3 With pressure bar 4-over-3 With pressure bar

Can system

(delivery)

Auto doffing (round cans)

Auto doffing (round or rectangulatr cans)

Auto doffing (round cans)

Auto doffing (round cans)

Auto doffing (round or rectangulatr cans)

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