Strip Tension Spikes During Start/Stop – Causes, Inspection, Repair & Prevention Guide for Roll Forming Machines

Strip Tension Spikes During Start/Stop

Roll Forming Machine Troubleshooting & Repair Guide

Strip tension spikes during machine start and stop cycles are a common operational issue in roll forming production lines. These spikes occur when the tension in the steel strip suddenly increases or decreases as the line accelerates or decelerates.

Instead of maintaining smooth, controlled tension, the strip experiences rapid changes in pulling force, which can cause feeding instability and material deformation.

If not controlled, tension spikes can lead to several production problems including:

• Strip snapping or tearing
• Coil slipping on the mandrel
• Strip jerking at the entry section
• Profile dimensional variation
• Roller impact loading
• Increased machine wear

For manufacturers producing metal roofing panels, cladding sheets, structural decking, purlins, trims, and other roll formed products, maintaining stable strip tension during machine acceleration and deceleration is essential for smooth production.

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

Causes of Wear or Failure

Strip tension spikes during start and stop cycles usually result from improper synchronization between line components or incorrect machine settings.

Decoiler Brake Misadjustment

If the decoiler brake is too tight or too loose, it may not respond smoothly to changes in line speed.

This can cause sudden increases or decreases in strip tension.

Sudden Machine Acceleration

If the roll forming line accelerates too quickly during startup, the strip may be pulled sharply from the coil.

This rapid force increase creates a tension spike.

Abrupt Machine Stops

Emergency stops or rapid deceleration can create sudden tension changes in the strip.

This may cause the strip to snap or shift unexpectedly.

Feeder Synchronization Issues

If a feeder or leveling unit is installed but not properly synchronized with the decoiler and roll forming machine, tension spikes may occur during speed changes.

Coil Weight Variation

Heavier coils may require greater torque to unwind.

If the brake system does not compensate correctly, tension spikes may occur.

Control System Calibration Problems

Modern roll forming lines rely on electronic control systems to coordinate equipment speed.

If these systems are improperly calibrated, tension fluctuations may occur.

Why It Happened and What Caused It

From a mechanical standpoint, strip tension spikes occur when the pulling force applied by the roll forming machine changes faster than the decoiler can respond.

During startup:

1. The roll forming machine begins pulling the strip.
2. The decoiler must release material at the same rate.
3. If the decoiler brake does not respond quickly enough, tension builds in the strip.

During shutdown:

1. The roll forming machine slows or stops.
2. The decoiler may continue unwinding briefly.
3. Slack may suddenly tighten as the strip movement stops.

These sudden changes in tension can stress both the strip and machine components.

Over time, repeated tension spikes may increase wear on rollers, guides, and feeding systems.

How to Inspect the Problem

Inspection Procedure

Careful observation during machine start and stop cycles helps identify tension spike problems.

Step 1 – Observe Strip Movement During Startup

Start the machine slowly and watch the strip between the decoiler and entry section.

Look for:

• Sudden strip tightening
• Jerking motion
• Strip vibration

Step 2 – Observe Strip Movement During Shutdown

Stop the machine gradually and watch how the strip reacts.

Signs of tension spikes include:

• Sudden slack tightening
• Strip snapping forward
• Coil movement on the mandrel

Step 3 – Check Decoiler Brake Operation

Inspect the decoiler brake system.

Ensure the brake applies smooth and controlled resistance during speed changes.

Step 4 – Inspect Feeder Synchronization

If a feeder or leveling unit is present, verify that it accelerates and decelerates in sync with the roll forming machine.

Step 5 – Inspect Strip Surface and Profile

Look for signs of tension-related problems including:

• Stretch marks
• Edge cracking
• Profile distortion

Step-by-Step Technician Guide – How to Fix

Several adjustments can reduce or eliminate tension spikes.

Method 1 – Adjust Decoiler Brake Tension

Set the decoiler brake to maintain stable strip tension during both startup and shutdown.

Avoid overly tight brake settings.

Method 2 – Adjust Machine Acceleration Settings

Modify the control system to allow gradual acceleration and deceleration.

Smooth speed changes reduce tension spikes.

Method 3 – Synchronize Line Components

Ensure the decoiler, feeder, and roll forming machine operate in coordinated speed control.

This prevents tension imbalance.

Method 4 – Use Strip Tension Control Systems

Some advanced roll forming lines use automatic tension control systems.

These systems monitor strip tension and adjust equipment operation accordingly.

Method 5 – Reduce Production Speed During Testing

Running the line at lower speed can help stabilize strip tension while adjustments are made.

Preventative Maintenance Tips

Preventing strip tension spikes requires proper machine setup and routine monitoring.

Maintain Decoiler Brake Components

Regular inspection of brake systems ensures smooth operation.

Calibrate Control Systems

Verify that machine control systems coordinate acceleration and deceleration correctly.

Inspect Feeder Synchronization

Ensure feeders operate smoothly with the rest of the line.

Train Operators on Startup Procedures

Operators should use gradual machine startup rather than sudden acceleration.

Monitor Coil Handling Equipment

Properly maintained decoilers and feeders help maintain stable strip tension.

FAQ Section

What are strip tension spikes?

Strip tension spikes occur when the pulling force on the strip changes suddenly during machine start or stop cycles.

Why are tension spikes a problem?

Sudden tension changes can cause feeding instability, material damage, and increased machine wear.

How can tension spikes be prevented?

Gradual machine acceleration, proper decoiler brake adjustment, and synchronized equipment operation help prevent spikes.

Can tension spikes damage roll forming machines?

Repeated tension spikes may increase wear on rollers, guides, and feeding equipment.

Do heavier coils increase the risk of tension spikes?

Yes. Heavier coils require greater force to unwind and may create tension fluctuations.

Should operators start the machine slowly?

Yes. Gradual startup helps maintain stable strip tension.

Machine Matcher Technical Support

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

Support services include:

• Roll forming machine troubleshooting
• Strip tension diagnostics
• Decoiler and feeder synchronization 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 tension spike problem
• Profile drawing and production speed

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