Vertical Lines in Knitted Fabric: Causes and Solutions in Circular Knitting Machines

Vertical Lines in Knitted Fabric: Causes and Solutions in Circular Knitting Machines

Vertical lines are a common fabric problem in circular knitting. They appear as lines running from the top to the bottom of the knitted fabric.

Sometimes the line is light and easy to miss. In other cases, it can be clearly seen and may make the fabric unsuitable for the final product.

A vertical line is often linked to one knitting position. The cause may be a damaged needle, poor needle alignment, a cylinder problem, a sinker issue, worn cams, or uneven yarn tension.

Finding the exact knitting position can make troubleshooting much easier.

What Causes Vertical Lines in Knitted Fabric?

A circular knitting machine has many needles working together to form the fabric. If one needle or another part at one position does not work correctly, it can create a repeated line in the fabric.

The first step is to identify whether the line appears at the same position throughout the fabric.

If it does, the machine position linked to that line should be checked carefully.

1. Damaged Knitting Needle

A damaged needle is one of the first things to check when a vertical line appears.

A needle may become:

• Bent
• Worn
• Broken
• Stiff
• Damaged around the hook
• Damaged around the latch

A damaged needle may not form the stitch in the same way as the other needles. This can create a visible line.

How to fix it

Stop the machine safely and check the needle linked to the defective area.

Replace the damaged needle with the correct needle. Then run a small amount of fabric and check whether the line has disappeared.

If the same problem returns, inspect the nearby parts as well.

2. Needle Alignment

Needles need to move correctly in their positions.

If a needle is not sitting or moving correctly, it may form stitches differently from the needles around it.

Poor needle alignment can be caused by:

• Incorrect needle position
• Dirt
• Worn needle parts
• Damage around the needle area
• Problems with the needle bed

How to fix it

Check the needle carefully and compare its movement with nearby needles.

Make sure it moves freely and follows the same path as the other needles.

If several needles in the same area show a problem, the issue may be related to the needle area rather than one needle alone.

3. Cylinder Issues

The cylinder holds the needles and plays an important role in the knitting process.

If there is damage, dirt, wear, or another problem around the cylinder, needle movement may not remain consistent.

This can lead to a repeated vertical line.

What to check

Look for:

• Dirt inside the needle area
• Damage
• Worn areas
• Loose parts
• Problems with needle movement

How to fix it

Clean the area according to the machine manufacturer's instructions.

If there is visible damage or the needle movement is not normal, the machine should be checked by a trained technician.

Do not try to make major cylinder adjustments without proper knowledge.

4. Sinker Problems

Sinkers work together with needles during the knitting process. A damaged or worn sinker can affect how the stitch is formed.

A sinker problem may create a vertical line that continues through the fabric.

Common causes

• Bent sinker
• Worn sinker
• Damaged sinker
• Dirt
• Incorrect sinker movement

How to fix it

Check the sinker near the position where the vertical line appears.

Compare its condition and movement with the nearby sinkers.

If it is damaged or badly worn, replace it with the correct part and test the machine again.

5. Cam Wear

Cams control the movement of needles during knitting.

Over time, cams can become worn. A worn cam may cause a needle to move differently from the other needles.

This can lead to repeated fabric lines or other stitch problems.

How to fix it

Inspect the cam area for:

• Wear
• Damage
• Dirt
• Loose parts
• Rough surfaces

If the cam is worn or damaged, it may need to be replaced.

If you are not trained to work on the cam system, get technical support instead of making major adjustments yourself.

6. Yarn Tension

Yarn tension can also affect the appearance of knitted fabric.

If one yarn path has different tension from the others, it can create a visible change in the stitches.

This may appear as a vertical line.

How to fix it

Check the yarn path from the yarn package to the knitting area.

Make sure:

• Yarn moves smoothly
• Yarn tension is stable
• Yarn feeder is working correctly
• Yarn is not rubbing against a damaged part
• Yarn package is feeding properly

Make small tension changes and test the fabric after each change.

How to Identify the Defective Knitting Position

Finding the exact machine position is one of the most useful steps when dealing with vertical lines.

Step 1: Stop the Machine

Stop the machine safely and inspect the fabric.

Step 2: Mark the Line

Mark the vertical line on the fabric so you can track its position.

Step 3: Follow the Fabric Back to the Machine

Look at the point where the line was formed and identify the machine position that matches it.

Step 4: Check the Needle

Inspect the needle at that position.

Look for bending, wear, hook damage, or poor movement.

Step 5: Check the Sinker

Inspect the sinker working near that needle.

Step 6: Check the Cam

Look at the related cam area for dirt, wear, or damage.

Step 7: Check the Yarn Path

Make sure the yarn feeding the affected position is moving correctly.

Step 8: Run a Test

After making the required correction, produce a small amount of fabric and check the same position again.

If the vertical line disappears, the cause may have been found.

What If the Vertical Line Does Not Disappear?

If the line remains after checking the needle, sinker, yarn, and basic settings, the problem may require a more detailed machine check.

Do not keep changing different settings without finding the cause.

Repeated changes can make troubleshooting more difficult.

A trained technician can check the cylinder, cam system, needle movement, and other machine parts when the problem is not clear.

How to Prevent Vertical Lines

Regular care can help reduce fabric problems.

Check Needles Regularly

Inspect needles for wear and damage.

Check Sinkers

Replace damaged or worn sinkers when needed.

Keep the Machine Clean

Remove dust, lint, and yarn waste from the working areas according to the machine instructions.

Check Yarn Tension

Make sure yarn tension remains suitable and stable.

Inspect Cams

Check cams for wear and damage during regular maintenance.

Follow Machine Settings

Use settings suitable for the yarn, fabric, gauge, and production requirement.

Keep Maintenance Records

Record repeated fabric problems, replaced parts, and maintenance work. This can help identify problems that return over time.

Can Machine Speed Cause Vertical Lines?

Machine speed may not directly create a vertical line, but an unsuitable speed can make an existing problem more noticeable.

If a vertical line appears after increasing production speed, reduce the speed and check the needle, yarn feeding, tension, and related machine parts.

The machine should always be operated at a speed suitable for its condition, yarn, fabric, and production requirements.

Choosing the Right Machine and Support

Fabric quality also depends on choosing equipment that matches the production requirement.

An automatic circular knitting machine can provide automated control and consistent production, but the machine still needs correct setup, suitable yarn, regular maintenance, and trained operators.

When choosing equipment, consider the machine gauge, fabric type, yarn, production volume, automation, spare parts availability, and technical support.

A reliable textile machinery supplier can also help you understand machine specifications and select equipment according to your production needs.

When Should You Get Technical Support?

Technical support should be considered when:

• The same vertical line keeps returning
• Several needles are damaged
• The cylinder shows signs of damage
• Cams appear worn
• Sinkers keep getting damaged
• Yarn tension cannot be kept stable
• The machine makes unusual noise
• The problem continues after basic checks

Repeated fabric defects can increase fabric waste, so finding the cause early can help reduce production loss.

Support from Ramana Machines

Ramana Machines supports textile businesses with circular knitting machinery sourcing, machine selection, installation assistance, operator training, spare parts, and after-sales technical support.

We help customers select suitable machinery according to fabric type, yarn, gauge, production requirements, and machine configuration. We also support China sourcing and imported textile machinery requirements.

If you are facing repeated vertical lines or other circular knitting problems, Ramana Machines can assist with suitable machinery, spare parts, and technical support based on your production needs.