Denim Fabric Weaving – Manufacturing Process, Methods, and technologies

The classical denim fabrics are made with open-end rotor yarn in both warp and weft direction. However, ring yarn, ply yarn, filament yarn, lycra core yarn, slub yarn are extensively used in denim to achieve some special effect, lustre, smoothness and comfort in denim products. The properties of denim finished fabric largely depends upon the fabric construction.

The warp and weft count influence several fabric properties such as weight, fabric tightness, cover, drape, hand, tensile strength, tear strength, and other fabric properties. All these parameters influence the durability and comfort of denim garments.

Weaving Manufacturing methods of Denim Fabrics

Cone winding machine

Winding is one of the most important operations which is mainly occurred in the spinning section. The creation of the large yarn packages that can be easily unwound called winding. The winding makes the subsequent machine operations more economical and easier.

Three zones of windings are:

1. Unwinding zone
2. Tension and clearing zone
3. Winding Zone

Features of Cone Winding Machine Used in Textile Weaving Sector

There are different key features of cone winding m/c which are pointed out in the following:

1. In cone winding m/c, reciprocating cams are attached with the traversing guide and attached with a shaft.
2. Also, the cam controls the yarn with the yarn guide.
3. Here, the cone is placed on the cone holder and kept in contact with the drum.
4. A drum is in opposition to each cone.

Objectives of cone winding machines

1. To prepare the bigger packages from smaller ring bobbins
2. To remove spinning faults.
3. To wax the material
4. To improve the quality of yarn

Requirements

The winding process should be accurate for accelerating the next process in fabric manufacturing. The winding process should fulfil the following requirements:

The winding process should be:

1. Easy
2. Maintain the characteristics of the yarn
3. Economical
4. Minimum winding faults
5. Package size and shape should be suitable to optimally used on the next machine

Auto-cone and Autoconing

Autoconing is the process of automatically making the end yarn packages without the need of feeding the small yarn packaged produced by the ring-spinning machines. The auto-coning machines in turn intelligently connected to transport the produced yarn-cones from the ring-spinning machines into the winding machines without any manual interventions of feeding the cones. Autoconer is the synonym for automatic package winding.

The aim of the modern automatic winder is to make the wound package as uniform as possible along with achieving higher production, better quality, and lower power consumption per kilo of product and flexibility.

The auto-coning department maintains the humidity and temperature according to the requirements throughout the year.

• Ideal humidity: 55~88%
• Temperature: 22~39.5 degree C

If winding tension is selected properly, the following tensile properties are not affected

• Tenacity
• Elongation
• Work to break

Excessive tension in the winding may deteriorate the above said tensile properties

Warping Section

Warping is the process of transferring a number of yarns from a creel of single end packages, forming a parallel sheet, on to a beam. The main objectives of warping include:

1. To get the required number of ends as per the set calculation
2. To get the required length of yarn on each beam of the set.
3. To wind a specific type of package required by the subsequent process

The most commonly used types of warping include direct/high-speed warping, sectional warping and ball warping. Objects of Warping:

• Preparation of warp yarn beam.
• Winding of yarn parallel to each other on warping beam.
• Reducing the yarn faults like thick and thin places, large knots etc.
• Winding the pre-determined length of yarn.
• Combination of small packages.
• Finding the long length of warp yarn.
• Preparing for the next process.

• Ball Warping is used for Rope Denim production
• Direct warping is used for sheet Denim production

Ball Warping is an intermediate process for storing yarn for transport, dyeing, or reserver; it does not produce a beam.

Ball warping

The main object of ball warping is to prepare the log for the rope dyeing machine. Here magazine type of creels is used for the creeling of yarns in the form of cheese. The number of ends taken one per the requirement of further processes that is for preparing the weavers beam. According to the number of ends in each group, the respective creeling is done to make the required number of logs to be used at the creeling zone of the rope dyeing machine.

The length of rope on the log is generally 12830 meters the sheet of yarns pass through the lease reed where lease are inserted these facilities denting the long the chain beaming. Lease are inserted at regular intervals which can set automatically on the machine, generally on every 100 meters, the lease is inserted, the lease also helps in yarn separation after sizing.

Ball Warping Process

In ball warping, 350 to 500 yarn ends are pulled from the creel. The yarns then pass through a comb-like device (reed), which keeps each warp yarn separate and parallel to its neighbouring ends.

At intervals of every 1000 to 2000 yards, a lease string is placed across the sheet of warp yarns to aid yarn separation.

The yarns then go through a funnel-shaped device called a trumpet or condenser, which collapses and condenses the sheet of yarn into rope form.

• The rope is wound onto a long cylinder called a log on a machine called a ball warper.
• Indigo dyeing will take place in rope form.

1. Packages of yarn are preconditioned before ball warping
2. Packages are loaded into the creel (larger lots- magazine transfer creel and smaller lots- swing gate or truck creel
3. Packages are placed on adapters. An adapter supports the package of yarn and ensures that the package remains aligned to the tensioning devices. Wooden plug type adapter is most effective as they require the least amount of exertion to remove the empty package.

The next step is threading the tensioner located at each yarn package

1. Post and Disk tensioner

   It has two posts mounted onto a flat base. two-round disks are placed onto each post. The yarn is threaded between the disk and wrapped around the post. One of the parts is movable so that the angle of the wrap can be varied. More tension can be added to the yarn by adding round weights onto the top disk.

   Advantages are

   1. Inexpensive
   2. does a marginally adequate job of maintaining yarn tension
   3. Simple to thread up
   4. Low maintenance requirements.

   Disadvantages are

   1. The yarn has a tendency to jump out from between the disks at the rear of the creel
   2. It is labour intensive- when different tension levels are required.
   3. There is more frequency of cleaning up
   4. It doesn’t control tension well at a higher speed.

2. The driven disk tensioner

   It also uses twin disk arrangement; however, the disks are supported from below- there are no posts. Tension is applied from above- there are weights or spring-loaded.

   A gear under each pair of disks is matched to another gear mounted on a continuous shaft that runs the length of the vertical tension post. This shaft is connected to a 4-rpm motor which rotates the disk.

   The advantage of disk rotation is

   1. Thread cutting prevention
   2. Dampens out variation due to ballooning action of yarn.
   3. There is more uniform tension
   4. Less effort required to change tension levels.

   Disadvantages are

   1. It is more difficult to thread up, there is more maintenance due to the electric motor used and at high speed, the tension control is not well.

Ball warping

In ball warping, 250–400 yarn ends are pulled from the creel. The yarns then pass through a comb-like device (also known as hack or reed), which keeps each warp yarn separate and parallel to its neighbouring ends. At intervals of every 1000 or 2000 m, a lease string is placed across the sheet of warp yarns to aid yarn separation for the re-beaming operation, which will occur later.

The yarns then go through a funnel-shaped device called a trumpet or condenser, which collapses and condenses the sheet of yarn into rope form. This device is located at the base of the warper head and traverses back and forth, guiding the newly formed rope of yarn onto a log. The rope must be wound at a constant tension to keep the yarns from tangling. The ropes are then used for dyeing with indigo in the rope dyeing range.

Ball warping is the process in which warping is performed in rope form onto balls and warp beam is prepared after the subsequent process. This type of warping is suitable for denim fabric manufacturing that involves a rope dyeing process. Ball warping is a two-stage process, initially, the warp yarns are wound in rope form on a cheese-like structure. The ball is wound on a special wooden core called “log” and rope dyeing is performed.

Ball warping calculations

The ball warping calculations are somehow similar to the direct warping calculations. The warping is usually planned with single or double creel. The length of yarn on the warp beam is decided to take into consideration the shrinkage % and the rejection % of the yarn and fabric. In general, for denim fabric, there is a 5% allowance for the rejection and 15-20% for the shrinkage of the fabric, i.e. to produce 10,000-meter denim fabric, the warping is usually 12,500-13,000 meters. The calculation will be clarified with the following example.

To produce a denim fabric with 10/s yarn having 67 ends/inch and 63” width, calculate the length of warp required.

Solution:

• The length of warp required will be calculated as:
• Total ends = 67×63 = 4221
• Number of logs = 12
• Number of ends/logs = 4221/12 = 351.75
• So, 9 logs will have 352 ends and 3 logs will be with 351 ends.

The plan for one creel will be as follows:

• Number of cones per bag = 16
• Cone weight = 100 / 16 = 6.25 lbs
• Length of yarn on one cone = 6.25 × 10 × 768.1 = 48006 m
• Length taken percentage is usually 99% because of variation in yarn length among different cones, to avoid length short problem.
• Length taken from cone = 48006 × 0.99 = 47526 m
• Warp length / log = length taken from one cone / Number of logs
• Warp length / log = 47526 / 12 = 3960.5 m
• The yarn requirement can be calculated as:
• Number of bags required = Number of ends on log / Number of cones in bag
• Number of bags required = 352 / 16 = 22 bags.

Indigo continuous Rope Dyeing process.

• Working speeds from 30 m/min up to 40 m/min
• Ropes featuring between 24 to 36 ropes, fully automatic coiler controlled by Siemens PLC
• Upper guide rolls with fluted profiles
• Continuous fresh dye liquor bath dosing system based on ml/Kg
• Independent magnetic flowmeters installed on each dye box for a balanced indigo liquor supply Standard rope dye range (8 Boxes) The standard rope Dye Range by Mezzera has been developed in order to give you the best solution and flexibility containing initial investment. Supported suitability and peculiar characteristics:
  • Double steamer (bottoming-topping/sulphur colour denim)
  • Medium-high indigo intensities achievable (4-5%)
  • Sulphur bottomed indigo casts all colours
  • Sulphur topped indigo casts all colours (last 2 indigo boxes with the independent circuit)
  • Sulphur dye all colours (last 2 indigo boxes + steamer)

Summary processes

Having passed the dyeing and oxidation rage the ropes are guided through 2 or 3 washing boxes to wash off excessive dye. In the last box, a softener is added to ease the opening of the ropes. They are dried in a series of cans. The dried ropes which contain 380 – 420 ends are then deposited into large coilers. Re-beaming with 300 – 380 ends per rope is easier.

Re-Beaming process (long-chain beamer)

These coilers are placed behind the long-chain beamer where the Re-beaming and opening of the ropes take place. In order to guarantee even yarn tension through Re-beaming on to a back beam ready for sizing the ropes are guided over a tension device which is placed approx.  10 -11 meters distance from the long-chain beamer.

Broken ends which very really happen during the process of the rope dyeing are repaired at this process stage. Initially, these machines were supplied without yarn stop motion but are available nowadays on special request. This is of major importance as lost ends, fluff, tail ends and yarn remnants can cause inferior performance in weaving.

Sizing Machine

Textile warp sizing, also known as tape sizing, of Warp yarn, is essential to reduce breakage of the yarn and thus production stops on the weaving machine. On the weaving machine, the warp yarns are subjected to several types of actions i.e., cyclic strain, flexing, abrasion at various loom parts, and inter yarn friction.

With sizing, the strength—abrasion resistance—of the yarn will improve and the hairiness of yarn will decrease. The degree of improvement of strength depends on adhesion force between fibre and size, size penetration, as well as encapsulation of yarn. Different types of water-soluble polymers called textile sizing agents/chemicals such as modified starch, polyvinyl alcohol (PVA), carboxymethyl cellulose (CMC), and acrylates are used to protect the yarn. Also, wax is added to reduce the abrasiveness of the warp yarns. The type of yarn material (e.g. cotton, polyester, linen) thickness of the yarn and the type of weaving machinery will determine the sizing recipe.

The sizing liquor is applied on warp yarn with a warp sizing machine. After the weaving process the fabric is desized (washed).

Sizing may be done by hand, or in a Sizing machine.

The so prepared beck beams are now sized in a sizing machine preferably with 2 size boxes. The size pick up varies between 8 – 12%. In Europe mainly modified starches with binders are used, whilst in the USA certain low % of PVA is applied in combination with starches by some companies.

Depending on the final finishing process (washed denim) with no filler also CMC gives excellent performance in weaving. Special size mixes for soft denim also can be applied and will be discussed separately. We recommend however not to use PVA for sizing of denim as a surface of denim may show a leather-skinned appearance.

Objectives of Sizing Process

The main objective of the sizing process is given below:

• To improve the weave ability of warp yarn.
• To improve the fibre-to-fibre adhesion force in the yarn.
• To prevent slippage of fibres in the yarn during weaving.
• “To make the yarn twist permanent by applying adhesive film on the yarn surface. The twist in unsized yarn tends to untwist due to rolling action during weaving so that it necessitates to be fixed”.
• To strengthen the warp yarn.
• To improve the abrasion resistance of warp yarn.
• To protect the yarn from being ruptured during passing through drop pin, the eye of heald wire and dent of reed.
• To reduce the hairiness of warp yarn.
• To improve the smoothness of warp yarn.
• To ensure good fabric quality in weaving.
• To ensure maximum efficiency of the weaving process.
• To prevent the development of electrostatic charges in the yarn during weaving.

General Sizing Calculations with an example:

The parameters received from warping regarding the set are given below:

• Total ends = 14640 ends
• Reed space = 126.20 inches
• Warp count = 40s
• Set( warp) length = 5000 metres
• Sizing waste = 70 metres per set length
• Actual warp length before sizing = 4930 metres
• Sized warp length = 5020 metres
• Warper’s beam = 2200 mm
• The number of beams = 20.

Now parameters required to size a beam are:

• Beamwidth = ?
• Denting order =?
• Beam width = Reed space (inches) + 20 mm
• = 126.20 inches + 20 mm
• = ( 126.20 X 25.4) + 20 mm
• = ( 3205.48 + 20) mm
• = 3225. 48 mm ( beam width)

Denting order

This is a very critical calculation in sizing. How to decide the denting order? When we group the warper’s beam s together, and we keep the zig-zag Reed in a downward position and initiate the sizing process, the width of the warp sheet is equal to the width of the warper’s beam.

Now sizer brings the reed in an upward position. The pointed dents of zigzag reed penetrate the warp sheet and the warp and automatically get passed through the dents of the reed. The ends density at both the selvedge and at the remaining sheet vary due to the difference in warper’s beams alignment.

Here sizer needs to correct the denting order at both the selvedge.

Now the question arises, how to find the correct denting order?

The approximate number of dents used  = number of reed stripes X dents per reed stripes

• = 25 X 60 dent
• = 1500 dents

Denting order calculation sheet is given below:

The difference in the denting order is corrected by expanding or reducing the width of the zigzag reed.

• Warping for slasher sheet dying and sizing

Direct warping for slasher sheet dying and sizing

Warp yarns run along the length of fabric and weft yarns go across the width of the fabric. Warping is the preparation of yarn to weave fabric. It is the transfer of many yarns from the creel of single packages to a beam. The yarns will form a parallel sheet of yarn wound onto the beam.

Productivity in Direct Warping

Warping means winding the yarn in a particular beam at a uniform tension and yarn are stay parallel. The productivity of warping depends on various parameter such as how many numbers of creel how many actual creels used and also depends on the running time of the warping machine. If the machine is run with greater efficiency, then it possible to make the required number of beams asset wise and usually use as much as 320 or 346 to make a beam of 22000 m or 11000m length and also requirement wise beam.

In the direct warping machine, we observed how much time to make a beam of the required length to collect data.

Details Information about direct warping