DENIM FABRIC PRODUCTION

What is denim fabric

Denim is a strong, durable fabric constructed in a twill weave with indigo and white yarns. The blue/indigo yarns are the lengthwise or “warp” threads (parallel to the selvage). The white yarns run across the fabric width (the weft threads). Denim is traditionally woven with 100%-cotton yarn; however, today it’s blended with polyester, to control shrinkage and wrinkles, and Lycra to add stretch.

Usually the weave is a 4- heald shaft warp-faced twill with the twill to right or to the left. Denims are particularly strong in the warp direction, where the fabric is subjected to greater wear. The standard denim, is made with indigo-blue dyed warp yarn and gray filling.

Yarns used in denim fabric Production:

Yarn Used: 1. Rotor Yarn 2. Ring Yarn 3. Slub Yarn 4. Polyester 5. Lycra Yarn

Classification of denim fabric

( According to use) 1. Regular

2. Ring

3. Rotor

4. Slub

5. Cross Slub

6. Stretch

6. Polyester

7. Polystretch

Regular fabric: 1. There is no mixing of count both in warp & weft

2. Only one count is used so no count variation

3. The fabrics are so called 100% cotton, 100% ring

etc according to yarn used to produce the fabric

100% cotton Ring Denim

Ring fabric: 1. This fabric is produced by mixing count or using two or more counts.

2. There is no slub yarn used in this type of fabric

3. This mixing is done in warpers beam using shets of different counted yarn

4. There is ring effect or horizontal straight line is formed in Ring fabric

Ring Fabric

Prep

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Fini

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Process Flow Chart

Yarn in Cone

Warping

Pre-treatment Indigo

DyeingDryingSizingDrying

Beaming

Weaving

Singeing Softening Skewness Sanforizing Calendaring

Mercerizing Stentering

Desizing

Resin FinishingInspection

Packing Delivery

For Weft Yarn

Yarn in Cone

For Warp Yarn

Warping:

Definition:

In general terms, warping is transferring many yarns from a creel of single-end packages forming a parallel sheet of yarns wound onto a beam or a section beam.

Types of Warping: ( In Partex Denim)There are Two types of warping, which are as follows:

1. Direct Warping2. Ball Warping

Direct Warping:

In direct warping, the yarns are withdrawn from the single-end yarn packages on the creel and directly wound on a beam.

Direct warping can be used to directly produce the weaver’s beam in a single operation. This is also called direct beaming

Figure: High speed/Direct warping

Ball WarpingBall Warping is mainly used in manufacturing of denimfabrics. The warp yarns are wound on a ball beam in theform of a tow for indigo dyeing. After the dyeing process,the tow is separated and wound on a beam. This stage isalso called long chain beaming or re-beaming.

Figure: Ball warping

Warping M/C used in Partex Denim:

BENDIRECT WARPING MACHINEMachine Specifications:

NAME :BENDIRECT WARPING MACHINE

TotalMachine :02

Model :AG,CH-9240UZWILBENINGER2005

Origin :Germany

YearofInstallation :2005

Creelcapacity :Max.:520,Min.:372

WindingSpeed :Maximum1200m/min

MaximumBeamDiameter :1250mm

AirPressureRequired :5-8bar

AirConsumption 3

:2.5–3m/hour

Power :21-23KW

PressureofDrum :600daN

MaximumLengthofYarnCanWind :Around30000m

YarnCount :BothRing&OpenEndyarn

Dyeing & SizingTheory of Dyeing:

The whole process of dyeing is completed by four steps as follows:

1. Dye molecules come to the fabric surface from the dye bath.

2. Fibre absorbs the dye molecule from the outer surface of the fibre to the internal surface of the cellulose.

3. Migrates the dye molecules everywhere of the fibre molecules.

4. Anchoring or fixing the dye molecules to the fibre molecules by hydrogen or covalent bond.

Denim dyeing

Denim Dyeing:The classical jeans were produced out of indigo-dyed Denim fabric. The special character of this fabric –

only the warp thread is dyed makes it necessary to carry out dyeing in yarn form. The yarns applied for Denim were exclusively produced on ring spinning machines in former times. The development of OE yarns by applying smaller rotors with a spinning speed of up to 200 m/min has led to the application ofOE rotor yarns both for warp and weft. The yarns applied for weaving must be of high quality, a high fiber for strength, regularity as well as a small part of short-stapled cotton fibres belongs to the basic features of the denim yarn.

Dyes use for Denim: Ø Vat Dyes Ø Sulphur Dyes

Why Vat dye is used: (Mainly Indigo Class) 1. Vat dyes provide textile materials with the best colour fastness of all the dyes in common use

2. . Indigo is attractive for its pleasing blue colour and for the unique fading characteristics of garment dyed with it

Why Sulphur dye is used: (Mainly Black)

1. Sulphur dyes are widely used on cotton mainly because they are economical to use

2. They have good to excellent wash fastness and good light fastness in dark shades

Denim Dyeing Process: (Used in Partex Denim)

There are two processes in the practice for continuous denim dyeing:

1. Slasher dyeing 2. Rope dyeing

Rope Dyeing:

The indigo Rope dyeing technology for denim

production is considered a superior dyeing technology, where better uniformity of dyeing is

achieved than other Indigo dyeing technologies

like slasher dyeing.

Figure: Rope Dyeing Range

Features of Rope Dyeing:

1. Better uniformity of dyeing is achieved than other Indigo

dyeing technologies like slasher dyeing.

2. Today rope dyeing accounts for a large percentage of warp

yarn dyed for denim production

3. The system offers highest production, due to continuous

process, as there is no stoppage for set changes

4. Maximum continuity of shades and minimum danger of center

to selvedge shade variation can be achieved

Figure: Rope dyeing and subsequent sizing, Step 1: Ball Warper, Step 2: Rope Dyeing, Step 3: Long Chain Beamer, Step 4: Sizing

Slasher Dyeing: In continuous slasher/sheet dyeing and sizing machine, direct

warping beams are used, instead of ball warping logs in case of

Indigo rope dyeing system. The Slasher Dyeing machine is

capable of handling Ne count form 9/s to 30/s (OE and Slub both).

The yarns sheet from each beam is pulled over and combined with

the yarns from the other beams so that multiple sheets of yarns

can be made.

Figure: Sheet Dyeing Range

Relative merits and demerits Between Rope dyeing & Slasher dyeing:

Ø Generally rope dyeing denim range produces better quality of denim than slasher dyeing.

Ø Rope dyeing means for higher production and long runs. Ropes dyeing can more lots without

any stoppages at set change. In case of sheet dyeing, the machine remains stop at set change.

Ø In rope dyeing better dry and wet fastness properties in denim fabric can be achieved, than

sheet dyeing.Ø In sheet dyeing good quality yarn is

required, as mending of broken ends is very difficult in sheetdyeing. This problem is less in

rope dyeing.Ø Sheet dyeing produces more waste

than rope dyeing.Ø Lot to lot, set to set shade consistency

is better in rope dyeing,

Sizing: Definition:

The process of applying a protective adhesive coating upon the yarn surface is called sizing. This is themost important operation to attain maximum weaving efficiency

Objects of Sizing:

1. To improve the weave ability of warp yarn.2. To increase the tensile or breaking strength for cellulose yarn.3. To maintain good quality fabric.4. To reduce hairiness, weakness of textile materials.5. To remove electrolytic formation for synthetic or blended yarn.6. To increase elasticity.

Changes in Yarn due to Sizing:

1. Breaking strength: Increase

2. Abrasion Resistance: Increase

3. Stiffness: Increase

4. Frictional Resistance: Increase

5. Yarn Diameter: Increase

6. Extension: Decrease

7. Electrostatic Charger: Decrease

8. Hairiness: Decrease

Why Sizing is called Heart of Weaving:

1 Higher Strength

2. Higher Elasticity

3. Higher Smoothness

4. Higher yarn diameter

5. Higher weight of yarn

6. Lower static electricity

7. Lower weakness

8. Lower absorbency

9. Lower flexibility

10. Lower hairiness

11. Higher frictional resistance

Types of sizing according to application:

Ø Pure sizing: When sizing is done in yarn which produces unbleached fabric is called pure sizing.So, ingredients are on the weight of yarn 7 to 10%.

Ø Light sizing: This is used for dyeing and printing. 11 to 15% sizing ingredients are used on the weight of yarn.

Ø Medium sizing: For increase of strength and weight of the yarn 16 to 40% sizing ingredients are used on the weight of yarn.

Ø Heavy sizing: It is used to increase the weight of yarn. Above 40% sizing ingredients are used on the weight of yarn.

1. Pre Wetting Box

2. Three Pre wash box

3. Sheet Dyeing process (Regular,

Bottoming, Topping, Pure Black)

4. Three Post Wash Box

5. Pre-drying cylinder

6. Size bath

7. Post drying cylinder

8. Weavers beam winder

Machine process Sequence of Dyeing & Sizing

Dyeing:

As discussed above denim warp sheet is dyed with Indigo (Vat) dyes and sulfur dyes. There are some options in dyeing of warp sheet.

Ø Indigo (Regular): In this case we use indigo in all tanks. According to shade.

Ø Bottoming: In this case another dye is applied before dyeing with indigo. First the warp sheet is

dyed with sulfur dye (black color) and then it is washed and then dyed with indigo.

Ø Topping: In this case the warp sheet is dyed with indigo in start and then it is washed and then it is dyed with another dye (normally with sulfur).

Ø Pure Black: In this case the warp sheet is dyed with sulphur dye (black color) with high

concentration of color.

Controlling Point of Sizing:1. Viscosity of the size solution

2. Sizing machine speed

3. Size add-on levels

4. Concentration of the size mixture

5. Volume of the size box (both quantity and size level)

6. Condition of squeeze rollers

7. Squeezing pressure

8. Hardness of squeeze rollers

9. Diameter of squeeze rollers

10. Yarn count and size box warp density per unit space.

Weaving:

The process of producing a fabric by interlacing warp and weft threads is known as weaving.

Basic Weave Designs:

Ø Plain weaveØ Twill weave:

Zigzag twill Herringbone twill Broken twill

But Mostly 2/1, 3/1 RHT is used in Partex Denim

Weaving Machines used to produce denim fabric:

1. Rapier2. Projectile3. Air-Jet4. Water-Jet

But in Partex only Rapier & Airjet loom is used.

Air-Jet Weaving:Air-jet weaving is a type of weaving in

which the filling yarn is inserted into the

warp shed with compressed air. Air-jet system utilizes a multiple nozzle systems and a profiled reed.

Rapier Weaving:

In Rapier weaving, a flexible or rigid solid element, called rapier, is used to insert the filling yarn across the shed. The rapier head picks up the filling yarn and carries it through the shed. After reaching the destination, the rapier head returns empty to pick up the next filling yarn, which completes the cycle. A rapier performs a reciprocating motion.

Figure: Relay Nozzles Figure: Rapier head

PARTEX DENIM

Flow Process Chart for Denim Finish Line

Fabric Unwinding

Brushing

J-Box

Singeing

Brushing

J-Box

Softening

Skewness

Dryer - 1, 2

Mini Stenter

Sanforizing

Calendaring

Folding

th

Motor speed: 25-80 m/min

Protruding fibre removed by blower

Fabric store unit

gas Pressure: 1-2 BarBust removed by blower

Bust removed by blower

Fabric store unit

Softener Flacks used for soften the fabric

Strengthening the weft yarn

Steam pressure: 2 Bar

Control of fabric width

Fabric Shrinkage Control

Make the fabric surface uniformPrepare for next step

Some important terms in Denim finishing:Skewness Control:

The skewness in denim fabric, particularly in twill weave creates a serious problem in subsequent garment manufacturing and its washing. Leg twist is a major problem in denim manufacturing. Due to this problem the leg is rotated in the opposite direction of the twill of the fabric after laundering. Leg twist is assumed to be happen due to the directional yarn stresses. These are inherent in regular twill weave fabrics and developed during weaving. During washing the yarn stresses is relaxed which changethe regular position of interlacement between warp and filling yarns. Due to this reason the legs are twisted. Normally leg twist not shown on garment stage. It only observed after laundering of the garment. Although leg twist appears after first laundering and it increases progressively with repeatedlaunderings.

Figure: Fabric with skew Figure: Fabric without skew

In general, Z- twist cotton yarns generate right-handed skew.

All S- twist yarns exhibit left hand skew. In general open-end

yarns result in less skew than the ring spun yarns.

Figure: Woven fabric skewness

Sanforizing:

Sanforizing is a mechanical finishing process of treating

textile fabrics to prevent the normal dimensional

alternation of warp & weft. After sanforizing the

residual shrinkage of woven fabric may be zero.

The sole objective of sanforizing is to control the length wise shrinkage of fabric. The Maximum percentage of shrinkage depends on fabric construction and quality but controlled according to the customer specifications.

PARTEX DENIMMercerization:

Mercerization is a physio-chemical process where yarn (cotton) is treated with 15-25% caustic sodasolution at a temperature of 200-300C. It is necessary to hold the fabric under tension and washthoroughly.

Flow Process Chart for Mercerization

Fabric Unwinding

Bath-1

Bath-2

Bath-3

Stenter

Bath-4 to 7

Bath-8

Bath-9

Dryer - 1, 2

Fabric folding

th

Speed: 25-35 m/min

Dosing of NaOH at room temperature

Dosing of NaOH at room temperature

Normal water wash at roomtemperature

Width controlHot water wash at 90OC

Hot water wash at 90OC

PH control

Normal water wash at room temperature

Moisture remove and drying

Prepare for next process

Advantages of mercerization:

1. Increase tensile strength

2. Improve hygroscopicity

3. Improve dye affinity

4. Improve smoothness

5. Improve luster

6. Improve dimensional stability and physical compactness

7. 20-30% dye and chemical save while dyeing after mercerization.

PARTEX DENIM Desizing:Desizing is the process of removing size materials from fabric. This is done simply passing the fabricthrough some hot water bath for several times. Sometimes softener can be used for better removing ofsize materials and also for better soft hand feeling.

Flow Process Chart for Desizing Fabric Unwinding

J-box

Bath-1-6

Dryer - 1, 2

J-box

Fabric folding

th

Temporary fabric store

Normal water wash at 80-90 OC

Dryer, moisture remove

Temporary fabric store

Prepare for next process

th

Resin Finishing:Resin may be applied on the fabric surface to form a coating or it may be applied to the amorphousregion of the material to impart a crease resisting property. It is a permanent chemical finishing process.

Flow Process Chart for Resin

Fabric Unwinding

J-box

Fabric straighten roller

Roller Printing

Coating

Stenter/Heat setting

Rolling

Inspection Process:Fabric batcher is set at the back side of machine equipped with rollers which provides fabric unwinding. Inspection table is laminated white to enhance the defect identification. Four tube lights are provided to optimize the lighting. Measuring counter is provided in front of the inspection table for controlling length. It has forward, reverse, start and stop button controls. Inspection is carried out on white board table. The cloth is pulled over the white board table by a variable speed motor and different cloth defects are recorded for quality control purpose. They inspect the fabric according to 4 point system. After inspection fabric is wound on roller.

Inspection m/c

Four (4) Point System:

Size Of Defect (Length in Inches) Penalty Points

3 inches or less 1

Over 3 inches but less than 6 inches 2

Over 6inches but less than 9 inches 3

Over 9 inches 4

Faults are scored with penalty points of 1, 2, 3 and 4 according to their size and significance.

Quality Assurance Procedure:

Point Range Class Class NameUpto 20Points/100m. Class A Elite

Upto 20–30Points/100m. Class B Zenith

Upto 30–40Points/100m. Class C Insta

More than 40 Points/100m. Rejected Rejected

Inspection Calculation Formula = (Total Point ×36 ×100)/(Fabric length×Fabric width)

Conclusion:

Denim is an important fabric in day to day use. So we all should know the basic concept of this fabric. In Bangladesh denim production is growing very fast. So knowledge about denim fabric is a must.

Acknowledgement:

For preparing this presentation we got little time and as it is a vast knowledge about the denim fabric production details & clear concept is a must. Thanks to my group members who has helped me getting the best idea to prepare the presentation. We hope in near future we will be able to produce elite denim in our Country.

Prepared by:

1. S.M.ARIFUR RAHMAN

ID: 2008 1-009

2. TOSLIM HOSSAIN KHAN

ID: 2008 1-072

3. RUSSELL ANWAR

ID: 2008 1-080

( Department of Fabric Manufacturing

Technology)