Why Denim Fabrics are more prone to Skew or Twist?

Introduction:

Twisted leg is a common problem encountered in jeans manufacturing. The primary factor contributing to the twisted leg problem is the characteristics of the fabric used in jeans. Denim is typically woven using various techniques, and the structure of the weave significantly influences the occurrence of skew problems.

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What is Skew?

Skew in fabric refers to a condition where the warp and weft yarns, though straight, are not at right angles to each other. This distortion can cause the fabric to appear twisted or slanted, making it difficult to work with and potentially affecting the final garment's appearance.

In denim fabrics, especially those with a 3/1 twill weave, twisting or "skew" is a common issue observed after washing or wearing. This Skew originates from the unique structure of the denim fabric.

Why Does Denim Skew?

The unique structure of denim fabric is the primary reason for skew. Let's break down the key factors:

1. Unbalanced Yarn Tension

In woven fabrics, two sets of yarns—warp and weft—interlace with each other to form the fabric structure. Maintaining a balance in the tension of these yarns during weaving is essential for fabric stability. Any imbalanced in tension results in unbalanced forces within the fabric, leading to skew or twisting. Let's look into this in more detail:

• Warp Tension: Warp yarns run lengthwise and are held under steady tension on the loom to ensure consistent fabric width and stability. But if the tension is too high relative to the weft, it can increase the risk of skew.
• Weft Tension: Weft yarns, running widthwise, are inserted into the warp under specific tension. This tension must ideally match the warp yarn tension to maintain fabric stability. If weft tension is lower or higher than warp tension, it can cause the fabric to become imbalanced, can increase the risk of skew.
• ?Uneven Tension in 3/1 Twill Weaves: ?In simpler weaves like plain 1/1 or 2/2 twills, there is a balance between warp and weft tension. In these weaves, each warp yarn crosses an equal number of weft yarns, creating a more balanced interlacement.

But, in a 3/1 denim twill weave, each warp yarn passes over three weft yarns and then under one. Because of this uneven interlacement, the tension between the warp and weft yarns becomes unbalanced. This imbalance is one of the main reasons for the twist or skew that can develop in denim fabrics.

2. Diagonal Interlacement

In a 3/1 twill weave, each warp yarn passes over three weft yarns and then under one. This pattern is repeated in each row, but with a slight offset. The offset is typically one warp yarn, meaning that the weft yarn starts interlacing with a different warp yarn in the next row. Interlacing get repeated over the time creates a series of diagonal lines, known as Twill line that run across the fabric.

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• Torque Manifesting as Skew or Twist:

In a 3/1 Twill weave structure, each warp yarn floats over three weft yarns. As a result, warp yarns bear more tension than weft yarns. Because the yarns interlace in a diagonal pattern, the unbalanced tension accumulates along this diagonal direction. This accumulation of tension creates a rotational force, or torque, along the twill lines, causing the fabric to naturally twist or skew in the direction of the twill.

When the fabric undergoes processes like washing or other relaxation processes, the tension doesn’t relax uniformly across the fabric. This uneven relaxation causes the fabric to twist along the diagonal, manifesting as skew or twist in the fabric.

• For Right-Hand Twill (RHT) (where the twill direction is to the right), the twist or skew typically appears counterclockwise
• For Left-Hand Twill (LHT) (where the twill direction is to the left), the twist or skew generally appears clockwise

In summary, the combined effects of Unbalanced Yarn Tension and Diagonal Interlacement in Denim Fabric promote skew in the direction of the twill line.

Conclusion:

The unique structure of the 3/1 twill weave in denim fabrics plays a significant role in the development of skew, driven by imbalances in yarn tension and the inherent diagonal interlacement. Recognizing these factors is essential for manufacturers aiming to produce high-quality denim that maintains its shape and appearance over time.

Happy Learning ???