How to Prevent Arc-Shaped Fabric Problems in Circular Knitting Machine Production

In modern textile manufacturing, circular knitting machines play an essential role in producing high-quality knitted fabrics for garments, sportswear, home textiles, and industrial applications. With the continuous development of automated knitting technology, manufacturers increasingly focus on improving fabric consistency, production efficiency, and downstream processing performance.

However, during circular knitting operations, various fabric quality problems may occur due to mechanical conditions, tension imbalance, or improper machine adjustment. Among these issues, arc-shaped fabric deformation is a common but often overlooked problem that can significantly affect fabric appearance, winding efficiency, and subsequent production processes.

Arc-shaped fabric occurs when a knitted fabric tube loses its uniform tension distribution during production. Instead of maintaining a straight cylindrical structure after being unwound, the fabric spreads into a fan-like or curved shape. This deformation not only impacts fabric storage and transportation but also creates difficulties during cutting, printing, coating, and other finishing operations.

Understanding the causes of arc-shaped fabric and applying effective corrective measures are critical for circular knitting machine operators and textile manufacturers seeking stable production and improved product quality.

Arc-shaped fabric refers to a knitted fabric condition where the tension distribution across the fabric width becomes uneven. One side of the fabric is tighter, while the opposite side becomes looser. The tighter side naturally forms the inner arc, while the looser side expands outward and forms the outer arc.

When a fabric roll produced by a circular knitting machine is unwound and placed flat on the ground under a relaxed condition, the fabric does not remain rectangular or evenly spread. Instead, it presents a curved, fan-shaped appearance.

This phenomenon indicates that different areas of the fabric have experienced different levels of stretching and recovery during the knitting, traction, and winding processes.

In normal production conditions, circular knitting machines should maintain balanced fabric tension around the entire circumference. The fabric tube should be evenly stretched, guided, and rolled into a uniform cylindrical package. However, when tension differences occur on different sides of the fabric tube, some areas become more extended while others remain relatively loose.

As the fabric roll continues to accumulate, this imbalance becomes increasingly obvious. The fabric winding direction gradually shifts toward one side, causing the roll to become uneven and difficult to control. Large fabric rolls may eventually develop serious alignment problems, reducing production efficiency and increasing material waste.

Although arc-shaped fabric may appear to be a minor issue during knitting, it can create significant problems throughout the textile manufacturing process.

The first impact of arc-shaped fabric is the disruption of normal winding. Since one side of the fabric is tighter and the other side is looser, the fabric cannot maintain a stable rolling position. As production continues, the deviation becomes larger, making it difficult to produce large and uniform fabric rolls.

Uneven rolls may require additional manual adjustment, slowing down production and increasing labor costs.

In garment manufacturing, fabric cutting requires accurate alignment to ensure consistent dimensions and minimize waste. Arc-shaped fabric makes it difficult for cutting machines to recognize straight edges and maintain accurate positioning.

The curved deformation may lead to:

• Incorrect cutting dimensions
• Increased fabric waste
• Lower production efficiency
• Poor garment consistency

For manufacturers producing large quantities of apparel, these problems can significantly affect profitability.

Many knitted fabrics require additional processes such as printing, coating, lamination, or dye finishing. These processes depend heavily on stable fabric tension and accurate positioning.

When fabric edges are uneven due to arc-shaped deformation, printing patterns may become misaligned, coatings may not be evenly applied, and finished products may fail to meet quality standards.

Therefore, controlling fabric shape during knitting is an important step in ensuring high-quality downstream processing.

Arc-shaped fabric is usually caused by uneven tension distribution during fabric transportation and winding. Two major causes are commonly observed in circular knitting machine operations.

One of the most common reasons for arc-shaped fabric is uneven expansion force from the four expansion rods inside the fabric tube.

Circular knitting machines usually use expansion rods to support the inner surface of the knitted fabric tube. These rods help maintain fabric expansion, reduce wrinkles, and provide consistent friction during fabric transportation.

Under normal conditions, the four expansion rods should evenly contact the inner surface of the fabric tube and provide similar resistance around the circumference.

However, if two of the four rods fail to apply sufficient pressure, an imbalance occurs.

For example, assume rods 1 and 2 maintain strong contact with the fabric tube, while rods 3 and 4 have insufficient expansion force.

On the side supported by rods 1 and 2:

• The contact pressure between rods and fabric increases.
• Friction resistance becomes stronger.
• Fabric movement is slightly restricted.
• Yarn deformation increases due to pulling force.

Because knitted yarn has elasticity, it stretches when subjected to tension. When the fabric passes through the upper traction roller, the stretched yarn attempts to recover its original length. This recovery causes the fabric on this side to contract and become tighter.

Meanwhile, on the side supported by rods 3 and 4:

• Contact pressure is lower.
• Friction resistance decreases.
• Fabric transportation is less restricted.
• Yarn stretching and recovery are reduced.

As a result, this side remains relatively loose and forms the outer arc.

The difference between the tight side and loose side eventually creates arc-shaped fabric.

Another important cause of arc-shaped fabric is improper alignment of the upper traction rollers.

The traction roller system plays a key role in pulling knitted fabric upward and maintaining consistent fabric tension. If the two upper traction rollers are not parallel or have uneven contact pressure, fabric transportation speed may become inconsistent across the width.

This problem is especially common in clamp-type traction systems.

Several factors may cause roller misalignment:

• Uneven roller coating thickness
• Improper roller installation
• Aging or damaged coating materials
• Yarn accumulation on roller surfaces
• Foreign objects attached to the roller

For example, if one end of the traction roller becomes thicker because of coating problems or wrapped yarn debris, the two rollers cannot maintain uniform pressure.

One side may have a larger gap between rollers, causing insufficient clamping force. During fabric elevation:

• The side without enough pressure experiences fabric slipping.
• The fabric lifting speed becomes slower than the roller's linear speed.
• The opposite side remains tightly clamped and moves at normal speed.

This difference in transportation speed creates uneven fabric elongation.

The side with slower movement becomes tighter because it receives greater pulling force, while the other side becomes looser. Eventually, the fabric shifts toward the tighter side during winding, creating the arc-shaped appearance.

To eliminate arc-shaped fabric problems, manufacturers should focus on maintaining balanced mechanical conditions and regular machine maintenance.

The first step is to check and adjust the expansion rod system.

Operators should ensure that:

• All four expansion rods are evenly distributed.
• Each rod maintains proper contact pressure.
• The rods remain parallel with the fabric tube.
• The friction resistance is consistent around the circumference.

If one rod becomes loose or fails to expand properly, it should be adjusted immediately.

Regular inspection is recommended because long-term operation may cause:

• Mechanical wear
• Pressure reduction
• Position deviation
• Uneven fabric support

Maintaining balanced expansion force helps prevent tension differences and improves fabric winding stability.

The upper traction roller system should also be checked regularly.

Manufacturers should inspect:

• Roller parallelism
• Installation accuracy
• Surface coating condition
• Pressure balance
• Foreign material accumulation

If roller coating needs replacement, operators should completely remove old adhesive residues before applying new coating. Uneven coating thickness can easily create pressure differences and lead to fabric deformation.

In addition, yarn waste, fibers, and other foreign materials should be removed promptly from roller surfaces.

Proper maintenance ensures that both rollers maintain uniform gripping force and consistent fabric transportation speed.

Preventive maintenance is one of the most effective methods for reducing fabric quality problems.

A recommended maintenance program should include:

• Daily inspection of fabric tension conditions
• Regular cleaning of traction systems
• Checking expansion rod pressure
• Monitoring fabric roll shape
• Adjusting machine parameters according to fabric type

Different yarn materials and fabric structures have different elasticity and tension requirements. Operators should optimize machine settings based on production conditions.

Besides mechanical adjustments, production parameters also influence fabric deformation.

Important parameters include:

• Knitting speed
• Fabric pulling tension
• Take-down force
• Yarn feeding tension
• Fabric winding pressure

Excessive pulling force may increase fabric stretching, while insufficient tension may cause loose fabric formation.

Therefore, manufacturers should establish appropriate operating standards for different fabrics and yarn types.

With increasing demand for high-quality textiles, manufacturers must pay greater attention to fabric consistency and production reliability. Problems such as arc-shaped fabric not only reduce product quality but also increase production costs through additional correction and material waste.

Modern circular knitting machines are becoming increasingly intelligent, incorporating advanced tension control systems, automatic monitoring technologies, and digital production management solutions. These technologies help manufacturers detect abnormal tension conditions earlier and maintain stable fabric output.

However, even with advanced equipment, proper mechanical adjustment and regular maintenance remain essential. Understanding the relationship between expansion rods, traction rollers, fabric tension, and winding performance enables operators to solve problems quickly and improve overall production efficiency.

Arc-shaped fabric is a common quality issue in circular knitting machine production caused mainly by uneven tension distribution. Insufficient pressure from expansion rods and misalignment of upper traction rollers are two major factors contributing to this deformation.

The problem can negatively affect fabric winding, cutting accuracy, printing quality, and downstream processing efficiency. To prevent arc-shaped fabric, manufacturers should ensure uniform expansion rod contact, maintain properly aligned traction rollers, perform regular equipment maintenance, and optimize machine operating parameters.

By implementing effective preventive measures, textile manufacturers can achieve more stable fabric production, reduce material waste, and improve the overall quality and competitiveness of their knitted products.