Wrinkling Between Ribs – Causes, Inspection, Engineering Fixes & Prevention Guide for Roll Forming Machines

Wrinkling Between Ribs

Roll Forming Machine Forming Defect Troubleshooting Guide

Wrinkling between ribs is a roll forming defect where the flat sections of a panel located between structural ribs develop small waves, wrinkles, or buckles during or after the forming process. Instead of remaining smooth and flat, the panel surface between the ribs shows visible distortion.

This defect typically occurs during roll forming when the material experiences compressive stress or uneven metal flow between forming stations.

Wrinkling between ribs is particularly noticeable in wide panel sections where the flat areas of the panel must remain smooth for aesthetic and structural reasons.

This defect commonly appears in products such as:

• Metal roofing panels
• Standing seam roofing systems
• PBR and R-panel profiles
• Agricultural panel systems
• Structural roof deck panels
• Architectural metal wall panels

Typical signs of wrinkling between ribs include:

• Small waves or ripples in the flat panel area
• Buckling between structural ribs
• Surface distortion visible in reflected light
• Wrinkles that become more pronounced as panel length increases

If this issue is not corrected, it may lead to several production and installation problems including:

• Poor aesthetic appearance of panels
• Panel overlap misalignment
• Reduced structural performance in some profiles
• Increased scrap and rejected panels
• Customer complaints and warranty claims

For manufacturers producing roofing and cladding panels, preventing wrinkling requires careful control of forming stress distribution, roll tooling setup, strip tension, and material flow during the roll forming process.

This guide explains the mechanical causes, inspection procedures, engineering corrections, and preventative maintenance strategies used by experienced roll forming technicians to eliminate wrinkling defects.

Causes of Wear or Failure

Wrinkling between ribs typically occurs when compressive forces develop in the flat areas of the panel during forming, causing the metal to buckle.

Several factors may contribute to this condition.

Excessive Compression Between Forming Passes

During roll forming, the strip passes through multiple forming stations where the profile shape gradually develops.

If too much compression occurs between forming passes:

• The flat panel sections may experience compressive stress
• The material may buckle between ribs
• Wrinkling may appear along the panel surface

Improper roll gap adjustment is a common cause of this problem.

Improper Forming Pass Design

Roll forming must shape the strip gradually across several stations.

If the forming passes introduce too much deformation too quickly:

• Metal flow may become unstable
• The flat panel areas may compress excessively

Proper pass progression is essential for preventing wrinkling.

Uneven Strip Tension

Stable strip tension helps control metal flow during forming.

If strip tension fluctuates:

• Some areas of the strip may compress while others stretch
• The panel surface may develop wrinkles between ribs

Strip tension variation may originate from:

• Decoiler brake instability
• Feed roller slippage
• Loop control problems

Residual Stress in Steel Coil

Steel coils may contain internal stress from the steel mill rolling process and slitting operations.

If leveling equipment does not remove these stresses, the strip may distort during forming.

Residual stress often appears as wrinkling in flat panel sections.

Improper Leveler Setup

Levelers remove coil memory and stress from the strip before forming.

If leveling is insufficient:

• The strip may enter the roll forming machine with uneven stress distribution
• Wrinkling may occur during forming

Roll Tool Wear

Worn roll tooling may gradually alter the geometry of the forming passes.

If the tooling no longer guides the strip correctly:

• Metal flow may become uneven
• Compression may develop between ribs

Why It Happened and What Caused It

From an engineering standpoint, wrinkling occurs when the metal sheet experiences compressive stress that exceeds the material’s ability to remain flat.

During roll forming, the strip undergoes bending and shaping across multiple stations.

While bending occurs primarily at rib locations, the flat areas between ribs must remain stable and free of distortion.

However, if the metal flow is not properly controlled, the flat panel sections may experience compressive forces.

When these forces exceed the material’s buckling resistance, the metal surface forms wrinkles.

This phenomenon is similar to what occurs when a thin sheet of metal is compressed without sufficient support.

Wrinkling becomes more likely when panels have:

• Wide flat areas between ribs
• Thin gauge material
• High forming speeds
• Uneven forming pressure

Maintaining balanced metal flow across the strip width is therefore essential for preventing surface distortion.

How to Inspect the Problem

Inspection Procedure

Diagnosing wrinkling requires careful inspection of both the finished panels and the roll forming machine setup.

Step 1 – Inspect Finished Panels

Place panels under strong lighting and examine the flat areas between ribs.

Look for:

• Surface ripples or waves
• Small buckles in flat sections
• Distortion visible when light reflects off the panel

Step 2 – Measure Panel Flatness

Use a straight edge or flat inspection table to measure surface deviation.

Step 3 – Inspect Roll Gap Settings

Check roll gap adjustments across the forming stations.

Excessive compression may cause buckling.

Step 4 – Inspect Strip Leveling

Verify that the strip exits the leveler flat and free of coil memory.

Step 5 – Inspect Strip Tension

Observe whether strip tension remains stable throughout the roll forming line.

Step-by-Step Technician Guide – How to Fix

Correcting wrinkling requires reducing compressive forces and stabilizing metal flow during forming.

Method 1 – Adjust Roll Gaps

Slightly increase roll gaps in stations responsible for compressing the flat panel sections.

Method 2 – Improve Leveler Settings

Increase leveling penetration to remove residual coil stress.

Method 3 – Modify Forming Pass Progression

Distribute forming forces more gradually across the forming stations.

Method 4 – Stabilize Strip Tension

Ensure consistent strip tension throughout the roll forming line.

Method 5 – Replace Worn Roll Tooling

Install new rolls if tooling wear has affected profile geometry.

Preventative Maintenance Tips

Preventing wrinkling requires careful control of machine setup and material preparation.

Inspect Roll Tooling Regularly

Check roll surfaces for wear or damage.

Maintain Proper Leveling

Leveling removes coil stress before forming.

Monitor Strip Tension

Stable tension helps maintain smooth panel surfaces.

Maintain Machine Alignment

Proper alignment prevents uneven forming forces.

Train Operators on Setup Procedures

Correct machine setup helps prevent panel distortion.

FAQ Section

What causes wrinkling between ribs in roll forming?

Wrinkling occurs when compressive stress develops in the flat panel sections between ribs.

Why do flat areas of panels wrinkle?

If the metal flow is not balanced during forming, the material may buckle.

Can roll gap settings cause wrinkling?

Yes. Excessive compression from tight roll gaps may cause buckling.

Can leveling reduce wrinkling?

Yes. Proper leveling removes internal strip stresses.

Does thin material increase wrinkling risk?

Yes. Thin gauge material is more prone to buckling.

How can wrinkling be corrected?

Adjusting roll gaps, improving leveling, and balancing forming forces usually resolves the issue.

Machine Matcher Technical Support

If your roll forming line is producing panels with wrinkling or other forming defects, Machine Matcher technical specialists can help diagnose the issue and recommend corrective actions.

Support services include:

• Roll forming machine troubleshooting
• Roll tooling inspection and setup analysis
• Panel defect diagnostics
• Forming pass design review
• Remote engineering support

Submit your issue through the Machine Matcher Technical Support Desk:

Include the following information:

• Machine type
• Panel profile drawing
• Coil material specifications
• Photos showing the panel defect
• Production speed and roll setup

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