The document summarizes the process of denim manufacturing. It involves several steps: ball warping, rope dyeing, slasher dyeing, re-beaming, sizing, weaving, and finishing. Rope dyeing involves continuously feeding ball warps into a dye range for application of indigo dye. Slasher dyeing is an alternative to rope dyeing. Re-beaming separates ropes of yarn and keeps them parallel. Sizing increases strength and abrasion resistance. Weaving interlaces warp and weft yarns. Finishing includes singeing, skewing, pre-drying, and shrinking. The document also discusses the use of spandex in denim for stretch and

1. 1
DENIM MANUFACTURING
By
MANSOOR FAIZ CHEEMA
Firstly denim fabric was only manufactured from ring spun yarn, but now the different
combinations of ring, open-end yarns and core spun yarn with core of elastomeric yarn are used.
Process flow for manufacturing of denim fabric is as followed.
Figure 1
1.1Warping:
Warping is the process of transferring multiple yarns from individual yarn packages onto
a single package assembly. Normally, yarns are collected in a sheet form where the yarns lie
parallel to each other and in the same plane onto a beam, which is a cylindrical barrel with side
flanges. This is known as beam warping. For denim ball warping is done, in which 250 to 400
yarn ends are pulled from the creel. The yarns then pass through a comb-like device (sometimes
called a reed), which keeps each warp yarn separate and parallel to its neighboring ends. The
Yarn Spinning
Ball Warping
Rope Dyeing
Re-beaming
Slashing
Weaving
Finishing

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yarns then go through a funnel-shaped device called a trumpet or condenser, which collapses and
condenses the sheet of yarn into rope form.
Ball warping
Figure 2
1.2Rope Dyeing:
Denim is yarn-dyed fabric with the warp yarns dyed with indigo dye and the filling
yarns left un-dyed process. In rope dyeing, ball warps are continuously fed into the rope or
chain-dyeing range for application of the indigo dyeing. Typically, 12-36 individual ropes of
yarn are fed side-by-side simultaneously into the range. The ropes are kept separate from each
other throughout the various parts of the dye range. The dye is layered by using multiple
passes of rope into the soluble dye and then exposing to the air for oxidation. The ropes are
then dried .After drying, the ropes are coiled into the larger tubs.
After dyeing the color of the yarn is checked either visually or instrumentally. It is
possible for the denim fabric to be finished and sold without going through any drying process.
These fabrics are known as natural denims sometimes called as bull denims. It is also possible
to manufacture the fabric with both warp and weft dyed.

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1.3Slasher dyeing:
For certain manufacturers, the rope or chain dyeing of indigo is not possible or
desirable, so slasher dyeing has become a reasonable alternative method. A slasher is a range is
normally employed to apply size formulations onto warp yarns before weaving. Here the yarns
sheet from the warping beam is fed into the scouring section followed by a dyeing section
where the indigo is applied. Slasher dyeing ranges have a number of advantages and unique
characteristics.
Figure 3
1.4Re-beaming:
Beaming or re-beaming involves pulling the ropes of yarn out of storage tubs and moving
them upward to a guiding device. This upward travel allows the ropes to untangle before
nearing the beamer head. Once the ropes come down from the guiding device, they go through
tensioning rollers to help further the separation of the ropes before going through a comb at
the re-beaming head, which separates individual yarn ends and keeps them parallel to one
another.
1.5Sizing:
The main purpose for sizing warp yarns is to increase the strength of the warp sheet,
abrasion resistance; the protective coating also reduces the hairiness of the yarn. The beams
from the beaming process are creeled on the back of the machine. The yarns sheets re guided
into the size box. After leaving the size box the yarn sheets are squeezed and dried and are
wound onto a beam which is directly put onto the loom for weaving purpose. In sizing the
number of ends required for the specific fabric width is achieved. The size is applied to the
yarn consist of starch, PVA etc.

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1.6Weaving:
Fabric is woven by interlacing of two sets of yarns perpendicular to one another. Warp
yarns are fed from the loom beam and are then directed through drop wires, heddles, and a
comb-like device called a reed while the weft yarn is fed from larger packages located outside
of the machine. The sequence of interlacing two sets of yarn can be varied to produce many
weave design. The denim is mostly woven as 3/1 twill 2/1 twill.
Figure 4
1.7Denim finishing:
Finishing of denim fabric is carried out after weaving .the finishing procedure involves
the following steps:
 Singeing
 Skewing
 Pre drying
 Shrinking
 Drying
The grey fabric is brushed to remove the loose lint and fluff from the fabric surface.
The fabric is then singed in order to burn off the protruding fibers from the fabric surface.

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Normally the denim fabric is singed twice. The potential shrinkage of grey denim fabric varies
from 8-18%. Hence the denim fabric must be pre shrunk so that the finished fabric does not
show higher shrinkage during subsequent washing. Denim fabric is skewed during finishing
process as fabric is skewed during washings. Sometimes the fabric is treated with softeners and
lubricants to give the fabric soft and pleasing handle. After finishing cutting and sewing of
garment is done and then wet processes are applied to the garment.

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SPANDEX
Spandex is incorporated into cotton fabrics to impart a greater level of stretch and
recovery than can be achieved by cotton alone. Prevalent in women’s wear, but expanding into
other product categories, cotton/spandex blends can be found in knit goods such as skirts,
leggings, and tops, or in most all types of woven goods such as stretch jeans. Some features of
spandex are listed below:
 High elasticity and recovery
 Low moisture absorption
 Resistant to normal apparel exposure to sunlight
 Resistant to most common chemicals
Spandex is not degraded under normal acidic or alkaline conditions, and it is not usually
affected by small amounts of knitting oils and lubricants. However, it is known to lose strength
when subjected to prolonged UV radiation exposure or chlorine.
Stretch values may vary depending upon the fabric construction, the amount of spandex
used, the denier of the spandex, and the heat-setting conditions. Typical stretch levels for cotton
knit fabrics with spandex are in the 50-100 percent range thus spandex may in every course or in
alternating courses.
In woven goods, spandex may be found in the filling yarns, in the warp yarns, or in both.
Construction of the woven fabric is paramount in determining the achievable amount of stretch.
Typically, the spandex used in woven goods will be found in a core spun yarn; however, the
form in which the spandex is used depends upon the fabric construction, performance
requirements, and experience of the designer. The choice of denier depends on the aesthetic
properties that are desired. Stretch levels are typically 15-50 percent for woven structures.
2.1. Stretch Denim:
The popularity of stretch denims with SPANDEX (elastane) has increased significantly
in recent years. Consumers prefer the stretch denim fabrics combining classic cotton aesthetics
with improved fit and comfort. The denims containing spandex possess a higher extensibility and
recoverability, which can increase comfort and freedom of action in various types of jeans. Just a
small percentage of spandex (elastomeric yarn) will enhance appearance by approving shape

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retention, reducing wrinkles and bringing new fluidity and drape ability to garments. To create
stretch denim, which meets the high requirements of consumers and cutters, the right combined
elastic yarn, fabric formation, dye and finishing have to be chosen. Stretch Jeans can be made
body hugging or even loose, it provides ultimate comfort and gives great shape to your body. By
default Stretch Denim will be made body hugging unless you specify in the comment box of the
measurement form that you dont want body hugging. The waist/seat of Stretch jeans may
measure less than you order because they will stretch to much more than the waist/seat
measurement you will have specified.
2.1.1. Spandex Type Selection:
For cotton rich denim (cotton contain>96%), regular spandex or Heat-Set spandex is
used. Regular spandex can provide best stretch power. Heat-Set is a new elastane type which
provides better width and can be heat-set at temperatures that are 20o
C lower than conventional
elastane, or at tenter-frame speeds that are 20% to 50% faster. For no heat-set denim, heat-set
type can reduce denim stone wash shrinkage and definitely offers wider width of fabrics. Also,
heat-set type could reduce the shrinkage variation and width variation between lots and pieces of
denim products.
The right Spandex deci-tex choice is based on final fabric weight. 70D spandex is usually
chosen for most denims. However, for some lighter weight and heavy weight denims, 40D and
140D spandex can also be used.
Figure 5

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2.1.2. Stretch Denim Fabric:
 Primary considerations in weaving of stretch denim are fabric design and construction.
 The available stretch of the fabric is mainly dependent on the difference between the
maximum reed width and the fully relaxed fabric construction.
 Too tight a fabric structure and too high a yarn count and yarn twist factor will prevent
weft contraction, so that the fabric remains wider than the required width and lacking in
stretch ability.
 Stretch denims are usually of the 3/1-twill structure with the warp yarn floating on the
fabric surface.
 A wide 2 to 2.5 cm tape with alternate yarn floats on the face and back is preferred in
order to prevent selvedge from rolling or curing in loose denim structures.
 The weft yarns should be fully stretched during weaving to prevent the formation of
kinks.
 Weft supply package must be uniformly wound.
2.1.3. Finishing:
Stretch denims with spandex are finished to obtain the desired stretch, recovery and
dimensional stability and to meet the fabric width requirement. Generally speaking, the finish
processing of stretch denim containing spandex follows closely the operational sequence used for
conventional non-stretch denim with the exception of relaxation and heat-setting steps. In order
to obtain good denim fabrics with nice stretch, high recovery and low shrinkage, it is important
to carefully control processing condition of relaxation and heat-set procedures.
2.1.4. Heat Setting:
Heat setting is done to re-stretch and stabilize the fabric close to the desired width. The
fabric should be heat-set on a pin-tenter with much care given to width control and heat
distribution. The framing width will depend on the fabric weight, width, and stretch level. During
the heat-setting stage, the spandex is held under tension, and this result in a denier reduction that
corresponds to a reduction in power and in width retraction. More severe heat-set conditions
(higher temperature or slower speed) can produce denims with lower stretch, lower shrinkage

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Figure 6
Heat-setting temperatures for woven range from 360-385°F (182-196°C) and are chosen
according to the desired performance properties of the fabric. Because a small amount of
shrinkage remains in the spandex after setting and because heat-setting does not prevent the
cotton fiber from shrinking, the set width for “filling stretch” fabrics should be 5-15 percent
higher than the desired width to account for any additional shrinkage that may occur in wet
processing. To prevent curling or edge folding, the selvage should be constructed to
accommodate the width shrinkage.
2.1.5. No-Heat setting Denim:
Some times, stretch denim does not pass through heat set process and directly go to
garment manufacturers. In this case, fabric has very high shrinkage (normally higher than 13%),
high shrinkage variation and width variation. Special care must be taken in garment sizing and
pattern design, cutting and stone wash processing for such fabrics. Ensure the fabrics, which
makes up of a piece of garment, possess the same level of shrinkage, or come from a same piece
of denim. In this way, the garment defects related to shrinkage variation could be reduced
remarkably.
2.1.6. Sanforizing:
In Sanforizing, fabrics are first subjected to a fine water spray, steam and fed onto a
compression blanket at 80 PSI (551.6 kPa) nip pressure. A Palmer unit operating at 120 PSI

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(827.7 kPa) steam pressure, completes the treatment. During Sanforizing, fabrics get relaxation
in both warp and weft directions, which results in lower shrinkage.
2.2. FABRIC QUALITY PROBLEMS:
Following are most of fabric quality problems frequently met in stretch denims
containing spandex. Their consequence on garment manufacture and consumer application and
the prevent methods are also presented.
PROBLEM CAUSE AND REMEDY
Low Fabric Stretch  Redesign fabric structure with wider greige width or
less yarn end density.
 Allow fabric more relaxation.
 Reduce heat set temperature or time.
High Wash Shrinkage  High wash shrinkage and variation could cause
garment size variation, sew line uneven and garment
manufacturing difficult. The less shrinkage, the better.
 Make as much as possible comedown during
relaxation process by adapting less tension, more
processing time in hot water, higher hot water
temperature.
 Chose heat set procedure routine.
 Higher heat set temperature and longer time.
 Sanforize.
 Use Heat Set spandex.
Selvage Curling  Modify selvage pattern with alternate floats on face
and back.
 Increase selvage width.
 Preheat set.
 Cutting selvage on the loom.
 Reduce spandex draft.

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Fabric Width Variation  Use more than two packages of yarns as fill yarns.
 Keep tension uniform in package rewind, fill yarn
tension, weaving tension.
 Heat set fabric.
Fabric Skew  Fabric skew could cause jeans with twisted leg.
 Twist set or steam set core spun yarns.
 Alternating S and Z twisted yarns in weft.
 Select proper skew adjustment amount for skewing
mechanism during finishing operation.
 Wet fabric right before skewing operation.
Power Lost after Bleaching  As with all elastane, the chlorine bleach process can
cause significant deterioration in stretch/recovery
properties and it is as the customer’s own risk to treat
fabrics/garments in this way.
 Do not use chlorite bleach agent.
 If chlorite bleach used, keep pH value between 11-13,
strictly control chlorite content, process temperature
and time under low level ;
 Select Chlorine Resistant type of spandex.
 Use 3GT polyester to get the stretch which have good
chlorine resistance properties (but mind it that they are
not spandex).
 Higher denier of spandex.