Friday, November 27, 2020

WARP WINDING PROCESS, TYPES OF WARP WINDING MACHINES, PATTERNING, AND PACKAGE FAULTS

 

WARP WINDING PROCESS:

Warp winding may be classified in following categories:
Drum winding

Precision or spindle winding

DRUM WINDING:















In drum winding process, the package gets driven negatively. The package is mounted on the spindle which is able to rotate freely. When the surface of package touches the rotating traverse drum having helical groves in it, package starts to rotate due to surface contact of drum. In drum winding, the package is formed by a single thread which is laid on the package at appreciable helix angle so that the layers cross one another and give stability to the package. Since package is driven through surface contact, so that less elongation in the yarn is occurred . Due to surface contact there are chances of yarn rupture and hairiness in this process. The drum winding is suitable for spun yarn mainly. The packages formed by this type of winding has low winding density but they has more stability. The yarn do not get slipped normally in this winding package during unwinding and handling. Only one coil is used to make this packages. The cross winding method is used in drum winding process. The package formed by this method has lower winding density. Minimum number of yarn is wound.  Efficient and uninterrupted unwinding of yarn result in the package. Winding process is so simple and easy to handle. The rate of unwinding is high. The cone, cheese and big spool can be formed by this winding process.

ADVANTAGES OF DRUM WINDING:

The advantages of drum winding process are given below:
No need of flanges in the packages.
Efficient yarn unwinding during various weaving process.
Stability of package is high.
Less chances of yarn elongation.

DISADVANTAGES OF DRUM WINDING:

The main disadvantages of drum winding are as follows:
Number of turns per inch (degree of twist) in the yarn gets affected in drum winding process.
Small package size results.
Low winding density of yarn package.
Chances of yarn rupture are possible.

PRECISION WINDING OR SPINDLE WINDING:








In precision or spindle winding, the package is driven positively. The package is mounted on the spindle having positive drive. When the spindle rotates, it pulls the yarn and wind it on the package. The coils of yarn forms with the help of yarn traverse guide which helps to move the yarn from one end to another end of package thus coil formation takes place. Traverse guide makes to and fro motion with the help of a cam. In precision winding, successive coils of yarn are laid close together in a parallel or near parallel manner. It is used primarily for filament yarn. There is no chance of yarn rupture in this process but more yarn elongation occurs in this process. The package resulted in this process has higher winding density. Due to higher winding density, package contains higher amount of yarn on it. Packages are wound with a reciprocating traverse. Patterning and rubbing causes damage of packages. The precision winding package shows poor stability during unwinding and handling. Due to unstable package character, the rate of unwinding is lower.


ADVANTAGES OF PRECISION OR SPINDLE WINDING PROCESS:

The main advantages of precision winding are given
There is no chance of yarn rupture.

Flanges on the packages are not required.

Larger package size can be produced.

Side unwinding is possible. 

The turns per inch (degree of yarn twist) remains unchanged.

More compact package results in precision winding.

It is mostly useful in winding of filament yarn.

DISADVANTAGES OF PRECISION OR SPINDLE  WINDING PROCESS:

The disadvantages of precision winding machine are as follows:

The speed of winding machine is limited because of limited speed of yarn traverse guide.

Chances of yarn elongation are possible.

The package resulted in spindle winding process has low stability . 

The unwinding of the package of spindle winding process is little difficult. 

ANTIPATTERNING DEVICE OR RIBBON BREAKER:

Before knowing about anti patterning device, it is necessary to know about patterning or ribbon formation in yarn winding process. How and when does the ribbon formation take place?

Ribbon formation or patterning:

This is a yarn package defect. This defect gets occurred during yarn winding process. 'The patterning or ribbon formation (Ribboning ) can be defined as a yarn package defect to be occurring during yarn winding process, in which the yarn coils get laid on the top of the previous yarn coil'.
In other words, we can say that the yarn coils follow similar path repeatedly during winding. This repeatedly continuous yarn coils path causes patterning or Ribboning ( ribbon formation) in the yarn package getting wound.





This situation gets created when traverse ratio reaches to an integer value. It has been observed that some patterning also occurs when values of traverse ratios that differ from an integer by 0.5, 0.25 etc.

At the starting of winding, the diameter of empty package is less than traverse drum. As the winding gets begins, the package diameter increases rapidly. When the package diameter gets equal to traverse drum, the patterning zone gets started. The ratio between rotational speed of traverse drum and package  gets equal to whole number (1). As soon as diameter of package gets increased the patterning zone gets ended. This kind of situation created every time when the ratio between rotational speed between traverse drum and package gets equal to an integer ( whole number. The patterning can be classified as below:


Major patterning:

When the package diameter gets relatively large, the rate of increase of package diameter gets slow. We can say that diameter change takes long time. In this stage, the patterning results for long time.

Minor patterning:

This kind of patterning results at the starting of winding. Since the rate of change of package diameter gets very fast at the time of starting, so that the patterning persist for very short period.

ANTI PATTERNING DEVICE:

If a yarn package has patterning or Ribboning defect in it, the yarn unwinding gets difficult during uses of this kind of package. A lot of end breakages get occurred during yarn unwinding. There are different types of anti patterning ( Ribboning ) devices used to prevent the patterning or Ribboning defect in the yarn package. The some of anti patterning systems being used in different winding machines are given below:

Propack system of anti-patterning by Schlafhorst:

This anti-patterning device has been designed and developed by Schlafhorst. It is a cradle anti-patterning system. As we know patterning creates when the number of yarn coils laid on the package per double traverse is a whole number. At the time of ribbon formation, the ratio between traverse drum speed and package speed reaches a critical value. The The computer of the "propack system" continuously monitors the speed of traverse drum and package speed and determines the ratios between traverse drum speed and package rotational speed. Whenever computer reads that critical speed ratio is about to touch patterning zone, the propack system comes into action immediately. The propack system lowers the cradle pressure by a pre-determined amount. In this way, the rotational speed of the package also gets decreased below the critical patterning speed till the package diameter gets adjusted to a value above the pattern zone. After crossing the patterning zone, the propack system system again send a command to mechanism, and the cradle pressure immediately returns in it previous value.

Semi-conductor device (TRIAC) anti-patterning device:

The Muratec Mach(Japan) has developed this anti-patterning device. This is an electronic device. It works on the basis of semi-conductor. Anti-patterning action is achieved with the help of pre-feeding of programme for start and stop durations (period) of the traverse drum motor. In this way, the speed variation cycle gets adjusted. The speed of traverse drum and therefore, the package increases or decreases constantly to prevent the ratios of their speeds to touch the critical value which creates patterning.

Double pitch drum (anti-patterning device)

This anti-patterning system has been developed by Murata ( Japan). This anti patterning system is known as Pac21.  This monitor all those critical parameters which are cause patterning. When control unit of Pac21 reads that patterning zone is about to touch, it sends a command to change the position of yarn from one groove to another groove of the same drum to prevent the patterning. In this way, at the time of ribbon formation zones the groove position changing mechanism switch over the yarn from winding at 2W to 2.5W.  It is suitable for all counts, types of yarns and package shapes.

Computer Aided Package (C. A. P. ) anti-patterning device by Savio:

This anti-patterning device has been developed by Savio. It is an electronic device. The drum and package diameter ratio gets read and regulated with the help of a computerized system. Each winding head computer controls the yarn deposited on the package. When the system reads that the patterning zone is about to touch, it  automatically intervenes with a servomotor to modify the drive ratio between package and the drum. The Savio claims that this system produces perfect package without patterning.

DIFFERENT TPYES OF YARN PACKAGE FAULTS IN DRUM WINDING, CAUSES, AND REMEDIES:

Various types of winding faults occurring during winding are given below:

EXCESS YARN BREAKAGE: 

When the excessive yarn breakages get occurred during  drum winding process, the productivity of the machine gets affected. The poor yarn quality also gets resulted, if there is excessive end breakages during winding. The some common and important reasons creating excessive end breakages are given below:

• The winding tension is selected according to yarn count to be wound. If the winder don't maintain enough and proper yarn tension during winding, excessive end breakages result.  Excessive yarn tension always results in the form of unnecessary end breakages during winding. The winder should take proper care of the yarn winding tension.

Improper winding speed:

The winding speed greatly influences end breakage rate during winding process. The speed of winding machine is selected according to the yarn tensile strength, count, and thick and thin places present in the yarn to be wound.  The winding tension gets increased when the winding speed is increased. This increase in  tension causes end breakage. The yarn having poor tensile strength gets wound on lower winding speed. The thin and thick places present in the yarn always increase the chances of end breakages, so that the yarn having poor tensile strength and high imperfection should get wound at low winding speed.

Setting of slub catcher:

The improper slub catcher setting also causes excessive end breakage during winding process. The clearance between top and bottom blades of slub catcher is selected according to the yarn count. The low clearance causes end breakage. If clearance is more than required, the extra thick places can be passed into the yarn being wound on the package.

STITCHES IN THE YARN PACKAGE:

Some times, the yarn coils get laid outside the edges of the package. These outside laid coils are known as stitches in the package. These stitches causes very big trouble during unwinding of yarn. The end breakage rate gets increased due to stitches in the package. The bottom stitches are very serious problem in yarn unwinding. The nose stitches also create snarling and bunches formation during unwinding. 

 The main possible causes of stitch formation in winding package are given below:
.
The excessive traverse drum speed may result in the form of stitch formation in winding package.

Worn out cone holder causes stitch formation.

Huge variation in winding tension creates stitch formation in winding.

If operator releases the yarn on incorrect position at the time of restarting after knotting of yarn, the stitch formation takes place.

Improper mounting of package in the cone holder may result stitch formation in winding.

Worn out traverse drum causes stitch formation in winding.

RIBBON FORMATION OR PATTERNING:

 The main possible reasons of ribbon formation are given below:

If anti-patterning device is not functioning properly, it may cause patterning or ribbon formation in the resulting yarn package.

In correct setting or programming of anti-patterning device causes patterning in the package.

Improper grip of package on the package holder results in the form of ribbon formation.

ENTANGLEMENT OF YARN:

main possible reasons of yarn entanglement  of in the  package are given below:

Repeated knotter fibres produces yarn entanglement.

The yarn entanglement may be occurred due to strong suction pressure.

Faulty release of yarn by operator after knotting

Improper working of yarn break stop motion causes yarn entanglement.

Wild Yarn:

Yarn waste wrapped on hands of machine operator results wild yarn in the package.

Snarling in the yarn:

possible causes of snarling are given below:

Improper release of yarn after knotting or at the time of restarting.

Strong suction pressure in the slack tube

Inadequate setting of twist.

YARN RUPTURE:

Sometimes, ruptured yarn comes out from the package during unwinding. This ruptured yarn cause big trouble during weaving. The main causes of yarn rupture in the package are given below:

If stop motion is out of order or not working correctly, the package gets rotated continuously without yarn. The surface of the yarn gets ruptured due to abrasion between drum and package surface.

The rough or damaged surface of groves of traverse drum also causes rupture in yarn.

• If the yarn path gets ruptured at any place, the ruptured yarn results in the package during unwinding.

• Soft package:

It is very serious package defect. This defect causes yarn coils slippage during unwinding. The whole package gets rejected many times. This problem create due to low winding tension.

• Soft nose package:

If the nose of the package gets much soft, there may be serious problem during yarn unwinding.  Almost half of the package may be rejected.  This defect causes when the operator increases the yarn tension in the middle of the package.  When the winding re starts with increased yarn tension, the winding density gets increased. The top layer of package put pressure on bottom layer. Thus the nose of the package comes out of the package. Winder should not increase tension after starting the winding machine. We should adjust the yarn tension at starting time only.

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