Textile & Fashion World

Filling Yarns
Yarn must be wound properly and on a suitable package for high speed unwinding

Preparation Requirement for Knitting Yarn:

Weft Knitting

Schematic Way of Winding

The Unwinding Zone: 

To rewind the yarn on a new package, it must first be removed from the old package. This is accomplished in the unwinding zone. This zone merely consists of a creel, which holds the old package in an optimum position for unwinding. The common yarn withdrawal methods, side withdrawal &  over-end withdrawal.

The Tension & Clearing Zone: 

The next zone is the tension & clearing zone. It is in his zone that yarn receives the proper tension to provide an acceptable package density & build for further processing. This zone consists of a tension device, a device to detect thick spots or slubs in the yarn & a stop motion which causes the winding to stop in the case of a yarn break or the depletion of a supply package. The yarn is directed into this zone by a guide.

The Winding Zone: 

In this section, winding process is done here.
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Filling Yarns
Yarn must be wound properly and on a suitable package for high speed unwinding

Preparation Requirement for Knitting Yarn:

Weft Knitting

Yarn Tensioners are devices by the help of which tension is given to the yarn. This is an important device because it enables us to provide necessary tension to the yarn as it moves through the different parts of the mschine.

Types of tensioning device 

There are basically three types of method by which tension is applied to yarn. They are as follows

• Capstan method 
• Additive method 
• Combined method

Capstan Method

This is the simplest form of yarn tensioning device where the yarn is passed around posts where the tension on the yarn is provided from the friction between the posts and yarns.

This follows the classic law of

Output tension = Input tension x eµθ

Additive method

In this method the yarn is passed through the middle of two surfaces in contact. The force is applied from above to give suitable tension to the yarn.

Combined method

The combined system is a combination of capstan and additive method. This device is a complicated system which on allows the addition of tension. We cannot decrease the tension with this device. It is seldom used.

Important effects of tensioning device 

If the tension is too high then

• The yarn can be damaged 
• The rate of yarn breakage will be high 
• The elongation property of yarn will change

If the tension is too low then

• It can lead to unstable or loose package formation which will cause problems during unwinding

Variation in yarn in different parts of a wound package will cause undesirable effects

For man made filament yarn improper tension will cause

• Change in molecular structure 
• Variation in colour shades

For staple or spun yarn too high tension will cause

• Yarn breakage at thin places

Factors influencing the selection of Tensioners 

• The device must be reliable to control uniform tension 
• The device must be easily thread able 
• It must not introduce or magnify tension variation 
• It must not introduce variation in twist 
• It must not be affected by wear 
• It must be easily adjustable 
• It must not be affected by oil and dirt 
• It must not encourage dirt collection 
• It must be easily cleanable 
• The operating surface must be smooth 
• It must be cheap

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Piecing: Piecing is the finding & connecting of the ends on the packages. The connection between the ends can be made by knotting adhesion or welding but the former is by far the most common. Such connections are required whenever an end breaks or when a creeling operation has been completed.

Doffing: Doffing is the removal of newly wound packages & the replacement of these by empty packages which will receive yarn during the transfer process. It will be noted that creel packages are emptied as the packages to be doffed are filled.

Types of Winding
According to density:
1. Precision winding
2. Non precision winding
 

According to type of package:
1. Cone winding package
2. Pirn winding package
3. Flange winding package
4. Cheese winding package
5. Cop winding package
 

According to the build of the package:
1. Parallel winding package
2. Near parallel winding package
3. Cross parallel winding package
 

According to methods of drive:
1. Positive or direct drive
2. Negative or indirect drive
 

According to the future of automation:
1. Conventional winding
2. Modern winding

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Tensioning Device
Tensioning device, a device to detect thick spots or slubs in the yarn & a stop motion which causes the winding to stop in the case of a yarn break or the depletion of a supply package. The yarn is directed into this zone by a guide.

Functions of Tensioning Device:

1. To allow the maintenance of proper tension in the yarn in order to achieve a uniform package density.
2. The tensioning device also serves as a detector for excessively weak spots in the yarn which break under the added tension induced by the tension device.

Effects of Tension Variation:

1. Too high tension may damage the yarn whereas too low tension can lead a unstable packages which will not unwind cleanly.
2. In case of man made fiber high tension can cause molecular change which affects the dye ability, so that variations in tension ultimately show as apparently random variation in color shading.
3. In case of winding staple yarns, yarn tension may break thin place of yarn.

Requirements Which Influence the Choice of Tensioning Device:

• The device must be reliable.
• It must be easily threaded.
• It must neither introduce nor magnify tension variations.
• It must not introduce difference in twist.
• It must not be affected by wear.
• It must be easily adjustable.
• It must not be affected by presence of oil or dirt.
• It must not encourage the collection of dirt & lint.
• It must be capable of easy cleaning.
• The operating surfaces must be smooth.
• It must be inexpensive.

Types of Tensioning Device:

Tensioning device can be classified in 2 ways as follows-

1. Depending on the type of the working member acting on the yarn.
2. According to the working principle.

Depending on the type of the working member acting on the yarn the tensioning devices are the following types: 

• Ball type.
• Washer type.
• Disc type.
• Roller type.
• Comb type.
• Two zone type.

According to the working principle the tensioning devices are the following types:

1. Capstan (multiplicative) tensioner.
2. Additive tensioner.
3. Combined tensioner.
4. Automatic tensioner.

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