Under-Tension Causing Wave Formation – Causes, Inspection, Repair & Prevention Guide for Roll Forming Machines

Under-Tension Causing Wave Formation

Roll Forming Machine Troubleshooting & Repair Guide

Under-tension in the steel strip during roll forming production can lead to wave formation along the strip surface or edges before the material even reaches the forming passes. Proper strip tension is essential for keeping the material stable as it travels from the decoiler through the entry section and into the roll forming machine.

When the strip is not under sufficient tension, the material may become unstable and begin to form waves, ripples, or slight buckles along its length.

If this condition is not corrected, it can create several production problems including:

• Strip instability at entry guides
• Edge wave or center wave formation
• Uneven forming pressure
• Profile dimensional inconsistencies
• Surface quality defects
• Increased scrap material

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

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

Causes of Wear or Failure

Wave formation due to under-tension typically occurs when strip tension drops below the level required to keep the material flat and stable during feeding.

Low Decoiler Brake Tension

If the decoiler brake provides too little resistance, the coil may unwind too freely.

This allows excess material to feed forward and lose tension.

Excessive Strip Slack

Slack between the decoiler and the entry section may allow the strip to move freely and develop waves.

This often occurs when strip support is inadequate.

Inconsistent Feeding Speed

If the roll forming machine or feeder pulls the strip unevenly, tension may fluctuate and create waves in the strip.

Coil Memory

Steel strip retains internal stresses from the coiling process.

Without proper tension, the strip may attempt to return to its coiled shape, creating wave patterns.

Entry Table Roller Misalignment

If entry table rollers are uneven or misaligned, the strip may lose consistent support and develop waves.

Leveler Misadjustment

Improper leveling settings may fail to remove internal stresses from the strip, allowing waves to form under low tension.

Why It Happened and What Caused It

From a mechanical standpoint, wave formation occurs when compressive forces develop across the strip due to insufficient tension.

In a properly adjusted roll forming line:

1. The strip remains under controlled tension.
2. The material travels smoothly along the entry path.
3. Internal stresses are balanced.

However, when tension drops too low:

• The strip becomes unstable.
• Internal stresses are released unevenly.
• The material begins to buckle slightly along its surface.

These buckles appear as waves or ripples across the strip.

Once waves enter the forming passes, they may be permanently formed into the finished profile, causing quality problems.

How to Inspect the Problem

Inspection Procedure

Proper inspection helps determine whether wave formation is caused by under-tension.

Step 1 – Observe Strip Behavior at Entry

Run the machine at low speed and watch the strip entering the machine.

Look for:

• Ripples along the strip
• Edge waves
• Slight buckling before the first forming pass

Step 2 – Inspect Strip Tension Between Machines

Observe the strip between the decoiler and entry section.

Signs of low tension include:

• Slack strip sections
• Sagging material
• Loose strip movement

Step 3 – Check Decoiler Brake Settings

Inspect the decoiler brake and verify that it is providing sufficient tension to control coil unwinding.

Step 4 – Inspect Entry Table Rollers

Ensure entry rollers are properly aligned and rotating freely.

Poor roller support may allow waves to develop.

Step 5 – Inspect Finished Profiles

Check finished panels for:

• Surface ripples
• Edge wave patterns
• Dimensional inconsistencies

These may indicate wave formation before forming.

Step-by-Step Technician Guide – How to Fix

Several adjustments can eliminate wave formation caused by under-tension.

Method 1 – Increase Decoiler Brake Tension

Adjust the decoiler brake to maintain stable strip tension as the material feeds into the machine.

Method 2 – Reduce Strip Slack

Ensure the strip path between machines remains straight and controlled.

Remove excessive slack in the strip.

Method 3 – Adjust Entry Table Rollers

Ensure rollers provide consistent strip support.

Re-align or replace damaged rollers if necessary.

Method 4 – Adjust Leveling System

Modify leveling roll pressure to remove internal stresses from the strip before forming.

Method 5 – Reduce Production Speed During Adjustment

Operating the line at lower speeds may help stabilize strip tension while adjustments are made.

Preventative Maintenance Tips

Preventing wave formation requires consistent strip tension and proper equipment maintenance.

Maintain Decoiler Brake Systems

Regular inspection ensures the brake provides stable tension during operation.

Inspect Strip Support Equipment

Entry tables and rollers should support the strip evenly along its path.

Monitor Strip Tension During Production

Operators should regularly observe strip tension and feeding stability.

Maintain Leveling Equipment

Proper leveling removes internal stresses that contribute to wave formation.

Train Operators on Proper Setup

Operators should understand how tension affects strip stability and product quality.

FAQ Section

What causes waves in steel strip during roll forming?

Wave formation often occurs when strip tension is too low or internal stresses are released unevenly.

What is under-tension in roll forming?

Under-tension occurs when the strip is not held under sufficient pulling force to keep it stable.

Can wave formation affect finished products?

Yes. Waves may become permanently formed into the finished profile, affecting product quality.

How can wave formation be corrected?

Increasing strip tension, adjusting decoiler brakes, and improving strip support usually resolves the issue.

Does coil memory contribute to waves?

Yes. Internal stresses from coiling may cause waves if tension is insufficient.

Should coils with severe wave formation be rejected?

If the waves cannot be corrected during processing, rejecting the coil may be necessary.

Machine Matcher Technical Support

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

Support services include:

• Roll forming machine troubleshooting
• Strip tension diagnostics
• Decoiler and entry section 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 wave formation
• Profile drawing and production speed

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