Strip Twisting Before First Pass – Causes, Inspection, Repair & Prevention Guide for Roll Forming Machines

Strip Twisting Before First Pass

Roll Forming Machine Troubleshooting & Repair Guide

Strip twisting before the first roll forming pass is a common feeding issue that can disrupt production and affect profile quality. This problem occurs when the steel strip rotates slightly along its length before entering the first forming rollers.

Instead of feeding flat and straight into the machine, the strip begins to twist along its centerline, causing one edge to rise while the opposite edge dips.

If this twisting occurs before the first pass, it can lead to several operational problems including:

• Uneven strip entry into the forming rolls
• Entry guide misalignment
• Edge wrinkling or distortion
• Roller contact imbalance
• Profile dimensional inaccuracies
• Increased scrap material

For manufacturers producing metal roofing panels, cladding sheets, structural decking, purlins, trims, and other roll formed components, controlling strip stability before the first forming pass is critical for maintaining accurate forming and smooth machine operation.

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

Causes of Wear or Failure

Strip twisting usually occurs due to material stress imbalance, improper setup, or coil defects.

Coil Camber

If the strip has camber, one edge may travel a slightly longer path than the other when entering the machine.

This difference in path length can create twisting before the first pass.

Uneven Coil Tension

Uneven tension during coil unwinding may pull one edge of the strip more than the other.

This imbalance can cause the strip to rotate slightly along its length.

Misaligned Entry Guides

Entry guides that apply unequal pressure to the strip edges can create twisting forces.

If one side guide roller is tighter than the other, the strip may twist as it feeds.

Leveler Misadjustment

If the leveling unit is not set correctly, internal stresses may remain in the strip.

These stresses can cause the strip to twist as it exits the leveler.

Coil Edge Thickness Variation

If the strip edges differ slightly in thickness due to crown variation or slitting irregularities, the strip may twist during feeding.

Improper Strip Centering

If the strip is not aligned with the machine centerline, it may enter the forming rolls at an angle, causing twisting.

Why It Happened and What Caused It

From a mechanical standpoint, strip twisting occurs when uneven forces act on the two edges of the strip.

Roll forming machines are designed to process material that enters flat and evenly supported.

When the strip enters the machine:

1. The entry guides attempt to center the strip.
2. Internal stresses within the material may resist straightening.
3. Uneven edge tension causes the strip to rotate slightly.

This twisting motion may continue through the first few forming passes, affecting roller contact and forming pressure.

If not corrected, twisting can cause uneven forming and damage to machine components.

How to Inspect the Problem

Inspection Procedure

Identifying the source of twisting helps determine the appropriate corrective action.

Step 1 – Observe Strip Entry at Low Speed

Run the machine slowly and watch the strip entering the first forming pass.

Look for:

• One edge lifting
• Strip rotation along its length
• Uneven entry into rollers

Step 2 – Check Entry Guide Pressure

Inspect entry guide rollers.

Ensure both sides apply equal pressure to the strip.

Uneven guide pressure may cause twisting.

Step 3 – Inspect Coil for Camber

Unroll several meters of strip and lay it flat.

If the strip curves sideways, camber may be contributing to the twisting problem.

Step 4 – Inspect Leveler Exit

If the machine has a leveling unit, observe the strip exiting the leveler.

The strip should exit flat and stable.

Step 5 – Inspect Strip Edges

Look for:

• Burrs
• Edge damage
• Thickness variation

These conditions may create uneven feeding forces.

Step-by-Step Technician Guide – How to Fix

Several adjustments can correct strip twisting before the first forming pass.

Method 1 – Recenter the Strip

Ensure the strip enters the machine exactly on the centerline.

Adjust entry guides to maintain equal spacing on both sides.

Method 2 – Adjust Entry Guide Pressure

Entry guides should guide the strip, not force it.

Reduce excessive pressure from guide rollers.

Method 3 – Adjust Leveling System

If a leveler is installed:

1. Adjust leveling roll pressure.
2. Remove internal strip stresses.

Method 4 – Correct Uncoiler Tension

Ensure the uncoiler brake applies consistent tension across the strip.

Uneven tension may cause twisting.

Method 5 – Reduce Production Speed

Operating at a lower speed may help stabilize strip movement during troubleshooting.

Preventative Maintenance Tips

Preventing strip twisting requires proper setup procedures and material inspection.

Inspect Coil Material Before Production

Check the strip for camber, edge defects, and thickness variation.

Maintain Entry Guide Alignment

Entry guides should remain centered and operate smoothly.

Regular inspection prevents alignment problems.

Maintain Leveling Equipment

Proper leveling helps eliminate internal stresses that cause twisting.

Monitor Uncoiler Operation

Ensure the uncoiler brake system maintains steady strip tension.

Train Operators on Setup Procedures

Operators should understand how strip alignment affects forming quality.

FAQ Section

What is strip twisting in roll forming?

Strip twisting occurs when the steel strip rotates slightly along its length before entering the forming rollers.

What causes strip twisting before the first pass?

Common causes include cambered material, uneven guide pressure, misaligned entry guides, and uneven coil tension.

Can strip twisting damage the machine?

Severe twisting can cause uneven roller contact and increased wear on machine components.

How can strip twisting be corrected?

Adjusting entry guides, correcting strip alignment, and stabilizing tension usually resolves the issue.

Does strip camber contribute to twisting?

Yes. Cambered material may cause the strip to twist during feeding.

Should severely twisted material be rejected?

If the twisting originates from severe material defects that cannot be corrected, rejecting the coil may be necessary.

Machine Matcher Technical Support

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

Support services include:

• Roll forming machine troubleshooting
• Strip feeding diagnostics
• Entry guide alignment 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 of the strip twisting issue
• Profile drawing and production speed

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