What is Yarn Withdrawal?
When yarn is removed from the package during weaving, it is called the withdrawal of yarn, known as the unwinding of yarn.
Another way is that a withdrawal of yarn is an essential step in preparing the yarn for weaving. It involves moving the yarn from its storage forms, such as cones or spools, onto the weaving equipment for the weaving process. It is unwinding or removing the yarn from the package before using it on the loom. It is known as the “withdrawal of yarn.”
Types of Yarn Withdrawal
As far as yarn withdrawal methods are concerned, they can vary depending on the weaving technique, the type of equipment used, and the desired fabric structure of the fabric. It is generally accepted that yarn withdrawal can be classified into two categories. These categories are as follows:
- Side Withdrawal
- Over-end Withdrawal
1. Side Withdrawal
In this method, the spool is rotated during the withdrawal process in order to prevent the yarn from rotating as it is being withdrawn. The side withdrawal method can be used on flanged packages as it does not involve the yarn touching the flanges and could damage the yarn. During the yarn withdrawal process, the package needs to be rotated.
Advantage of Side Withdrawal
- There is no change in TPI in case of a side withdrawal. This means that the yarn twists remain the same throughout the process.
- Regarding side withdrawal, balloon formation does not occur.
- There is no rotation of the yarn when withdrawn from the machine.
Disadvantage of Side Withdrawal
- There is sometimes an uneven tension in yarn when unwinding of with side withdrawal systems. This can result in loose or tight sections of the wound package. There may even be yarn breakage or tangling problems in extreme cases.
- The maximum wind speed of side withdrawal unwinding systems is often limited. As a result, winding processes can be less productive, especially in high-speed production environments.
- In the side withdrawal process, the yarn may contact various mechanical parts, such as guides or tensioning devices. Maintaining or adjusting these components is important to prevent yarn abrasion, nicks, or other damage that could negatively impact the yarn’s quality and performance.
2. Over-end Withdrawal
During the winding section of the textile manufacturing process, an over-end withdrawal is used to remove material from the end of the yarn. This technique refers to a method by which yarns are pulled from spinning or processing packages at the top or over the end of a package during unwinding to remove them from the package. During over-end withdrawal unwinding, a rotating take-up roll or a winding mechanism above the package pulls the yarn from the package. It is important to note that the yarn package does not have to be rotated in this system.
Advantage of Over-end withdrawal
- Over-end withdrawal systems allow for better control of yarn tension during unwinding. As a result, packages are more consistent with uniform yarn tension throughout. A constant tension improves package quality, reduces yarn breakage, and improves overall process efficiency.
- Over-end withdrawal systems often allow for faster unwinding speeds than other methods. Yarn is drawn out of the package from the top, which speeds up yarn uptake. The increased speed can result in higher productivity and throughput, making them suitable for high-volume production environments.
- The over-end withdrawal system minimizes the stress and strain on the yarn during unwinding. As the yarn is gently withdrawn from the package, it is less likely to break, deform, or otherwise damage. The process is particularly beneficial for yarns that are delicate or sensitive.
- Over-end withdrawal systems can accommodate a broader range of package sizes. They can handle various package diameters and lengths without requiring significant adjustments or additional setup time. This versatility is beneficial when dealing with diverse yarn types and customer requirements.
- Over-end withdrawal does not require a flanged bobbin.
Disadvantage of Over-end Withdrawal
- Over-end withdrawal can sometimes lead to yarn tangling issues during unwinding. Tangles or knots may result from the yarn twisting or looping around itself. In order to minimize the risk of tangling, tension control, and yarn path management are essential.
- Some types of yarn may not be suitable for over-end withdrawal. In an over-end withdrawal system, some yarns, especially those with high elasticity or low cohesion, may not unwind smoothly or consistently.
- Over-end withdrawal systems may require more vertical space than other unwinding methods. Above the package is positioned a rotating take-up roll or winding mechanism that adds height to the setup. Accommodating multiple unwinding units in settings with limited vertical space can be challenging.
- It has been observed that there is scope for balloon formation.
- In the process of over-end withdrawal, the TPI yarn may be changed.
Differences Between Side Withdrawal and Over-end Withdrawal
|S/N||Side withdrawal||Over-end withdrawal|
|1.||In this method the yarn package is rotated when is unwound.||In this method, the yarn package is not rotated when yarn is unwound.|
|2.||The flanged bobbin is required for side withdrawal.||The flanged bobbin is not required for over-end withdrawal.|
|3.||The yarn twist per inch (TPI) is remained constant.||The yarn twist per inch (TPI) is not remained constant.|
|4.||There is no scope of balloon formation.||There is scope of balloon formation.|
|5.||The maximum wind speed of side withdrawal unwinding systems is often limited.||Over-end withdrawal systems often allow for faster unwinding speeds than other methods.|
|6.||This process is costlier than over-end withdrawal.||This process is not so expensive.|
|7.||This process is suitable for all types of yarn.||This process is not suitable for all types of yarn. Especially those with high elasticity.|
For yarn unwinding, several factors must be considered before deciding between side withdrawal and over-end withdrawal. The yarn is pulled horizontally from the package’s side, while the yarn is drawn vertically or inclined from the package’s top or over the package’s end for over-end withdrawal. Side withdrawal has many advantages, such as yarn path control, flexibility for different packages, and simplicity in threading. However, there are also limitations regarding yarn quality control, productivity, and suitability for certain fibers. A number of benefits can be derived from over-end withdrawal, including consistent yarn tension, faster winding speeds, reduced yarn stress, easier threading, flexibility in package sizes, and improved package formation. However, it may have disadvantages such as potential yarn tangling, limited package stability, increased package abrasion, and complexity in handling specialty yarns. When choosing between the two methods, it is important to consider yarn characteristics, production requirements, space availability, budget, and desired package quality. Identifying the most suitable yarn unwinding process for a given application will involve evaluating each method’s specific needs and trade-offs.