Over-Tension Stretching Strip Edges – Causes, Inspection, Repair & Prevention Guide for Roll Forming Machines

Over-Tension Stretching Strip Edges

Roll Forming Machine Troubleshooting & Repair Guide

Over-tension stretching strip edges is a material deformation problem that occurs when excessive pulling force is applied to the steel strip during roll forming production. When strip tension becomes too high, the edges of the strip may stretch more than the center section.

This uneven stretching can lead to several production problems including:

• Edge wave formation
• Strip distortion before forming
• Uneven forming pressure
• Profile dimensional inaccuracies
• Increased roller wear
• Reduced finished product quality

For manufacturers producing metal roofing panels, cladding sheets, structural decking, purlins, trims, and other roll formed components, maintaining balanced strip tension across the entire strip width is essential for stable forming and accurate product geometry.

This guide explains the causes of over-tension stretching, inspection procedures, corrective actions, and preventative strategies used by experienced roll forming technicians.

Causes of Wear or Failure

Over-tension stretching typically occurs when strip pulling forces exceed the material’s elastic limits during feeding or forming.

Excessive Decoiler Brake Resistance

If the decoiler brake applies too much resistance, the roll forming machine must pull harder to unwind the strip.

This increased pulling force can stretch the strip edges.

Incorrect Feeder Tension Settings

Some roll forming lines include powered feeders.

If feeder tension is set too high, the strip may be stretched as it enters the machine.

High Machine Pulling Force

Machines producing thicker or high-strength profiles may apply strong pulling forces during forming.

If these forces are not balanced correctly, strip edges may stretch.

Sudden Machine Acceleration

Rapid machine startup may create a sudden spike in pulling force.

This can stretch the strip before it stabilizes.

Material Yield Strength Differences

Some materials have lower yield strength and are more susceptible to stretching under tension.

Thin gauge steel is particularly sensitive to over-tension.

Misaligned Entry Guides

If entry guides apply pressure unevenly to the strip edges, localized tension may occur.

This may cause edge stretching.

Why It Happened and What Caused It

From a mechanical standpoint, over-tension stretching occurs when the pulling force applied to the strip exceeds the material’s ability to maintain uniform deformation.

During normal roll forming:

1. The strip is pulled steadily through the forming rollers.
2. Tension is distributed evenly across the strip width.
3. The material deforms uniformly during forming.

However, when tension becomes excessive:

• The edges may stretch more than the center.
• Internal stresses build across the strip width.
• Edge wave or distortion develops.

Once this stretching occurs, it may affect the forming process and lead to dimensional variation in the finished profile.

How to Inspect the Problem

Inspection Procedure

Identifying over-tension stretching early helps prevent product defects and machine wear.

Step 1 – Inspect Strip Edges Before Forming

Observe the strip as it enters the machine.

Look for:

• Wavy edges
• Slight rippling along the strip edges
• Uneven strip width

Step 2 – Check Strip Tension

Observe the strip tension between the decoiler and the roll forming machine.

Excessive tension may appear as a tight, rigid strip path.

Step 3 – Inspect Finished Profile Edges

Check finished products for:

• Edge waviness
• Profile distortion
• Uneven flange geometry

These may indicate edge stretching during forming.

Step 4 – Inspect Decoiler Brake Settings

Verify that the decoiler brake is not set excessively tight.

Too much braking force increases strip tension.

Step 5 – Monitor Machine Load

High pulling loads during forming may indicate excessive strip tension.

Monitor machine motor load indicators if available.

Step-by-Step Technician Guide – How to Fix

Several adjustments can reduce strip tension and prevent edge stretching.

Method 1 – Reduce Decoiler Brake Tension

Adjust the decoiler brake to allow smoother strip unwinding.

This reduces pulling force on the strip.

Method 2 – Adjust Feeder Settings

If a feeder is installed, adjust feeding pressure and speed to maintain balanced tension.

Method 3 – Modify Machine Acceleration

Gradual machine startup reduces sudden tension spikes.

Adjust control system acceleration parameters.

Method 4 – Recenter Entry Guides

Ensure entry guides apply equal pressure on both edges of the strip.

Uneven guide pressure may create localized tension.

Method 5 – Reduce Production Speed

Lower speeds may reduce strip tension while troubleshooting.

Preventative Maintenance Tips

Preventing strip edge stretching requires proper tension control and machine setup.

Maintain Decoiler Brake Systems

Regular inspection ensures the brake applies smooth and consistent tension.

Monitor Strip Tension During Production

Operators should regularly observe strip tension between the decoiler and the machine entry.

Inspect Entry Guide Alignment

Properly aligned guides help distribute strip tension evenly.

Use Gradual Machine Startup

Smooth acceleration prevents sudden tension spikes.

Train Operators on Tension Adjustment

Operators should understand how decoiler brake settings affect strip tension.

FAQ Section

What causes strip edges to stretch in roll forming?

Excessive strip tension during feeding or forming may stretch the strip edges.

What are the signs of over-tension stretching?

Common signs include edge waves, uneven strip width, and profile distortion.

Can excessive tension damage roll forming machines?

Yes. High tension increases wear on rollers, guides, and feeding equipment.

How can strip tension be reduced?

Adjusting decoiler brake tension, feeder settings, and machine acceleration can reduce strip tension.

Does thin material stretch more easily?

Yes. Thin gauge materials are more susceptible to stretching under tension.

Should stretched material be rejected?

If the deformation significantly affects product quality, the affected material may need to be rejected.

Machine Matcher Technical Support

If your roll forming line is experiencing strip tension problems, feeding instability, or profile distortion, Machine Matcher technical specialists can help diagnose and resolve the issue.

Support services include:

• Roll forming machine troubleshooting
• Strip tension diagnostics
• Decoiler and feeder inspection
• Production line performance evaluation
• Remote technical assistance

Submit your issue through the Machine Matcher Technical Support Desk:

Include the following information:

• Machine type
• Coil width and thickness
• Photos or videos showing the strip edge stretching
• Profile drawing and production speed

Our technicians will review the information and provide step-by-step recommendations to restore stable production.