Denim Fabric Weaving – Manufacturing Process, Methods, and technologies

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.