Changeover Procedures Between Coil Thicknesses in PBR Machines

Step-by-Step Method to Switch Gauge Without Scrap, Damage or Downtime

Changing between coil thicknesses (gauge changes) in PBR (Purlin Bearing Rib) roll forming production is one of the most common causes of:

• Scrap spikes

• Rib height variation

• Oil canning

• Bearing overload

• Tool chipping

• Shear burr

• Panel width drift

Most factories treat thickness changeovers as “minor adjustments.”

They are not.

Every gauge change alters:

• Forming pressure

• Springback behavior

• Strip stiffness

• Drive torque

• Shear load

• Guide pressure

If you do not adjust correctly, you damage tooling and lose profit.

This guide provides a structured procedure for switching safely and accurately between coil thicknesses.

Understand What Changes When Gauge Changes

When moving from thinner to thicker material:

• Forming force increases

• Bearing load increases

• Motor current increases

• Springback increases

• Rib compression must increase

• Shear load increases

When moving from thicker to thinner:

• Over-compression risk increases

• Surface marking risk increases

• Oil canning risk increases

• Roll gap must be reduced carefully

Gauge change is a mechanical recalibration event.

Before Changeover: Preparation Checklist

• ✔ Confirm target thickness (actual measured gauge, not label)
• ✔ Confirm tensile strength of new coil
• ✔ Confirm machine rated thickness range
• ✔ Review roll gap reference values
• ✔ Clean tooling before adjustment
• ✔ Remove previous coil completely

Never assume two 26ga coils behave the same.

Material yield strength varies significantly.

Lockout & Safety

Before mechanical adjustment:

• ✔ Stop machine
• ✔ Lock out power
• ✔ Release hydraulic pressure
• ✔ Remove material from line
• ✔ Secure shear system

Never adjust roll gap with live drive.

Roll Gap Adjustment Procedure

This is the most critical step.

Step 1: Establish Baseline Reference

Record current settings:

• Roll gap shim position

• Adjustment bolt turns

• Stand pressure indicators

Documentation allows repeatability.

Step 2: For Thicker Material

When increasing gauge:

• ✔ Open roll gap slightly first
• ✔ Insert material
• ✔ Gradually tighten until correct rib height achieved
• ✔ Avoid immediate full compression

Over-tightening instantly overloads bearings.

Step 3: For Thinner Material

When decreasing gauge:

• ✔ Reduce roll compression carefully
• ✔ Check panel width frequently
• ✔ Avoid over-squeezing
• ✔ Watch for surface marking

Thin material is sensitive to over-forming.

Step 4: Adjust Stands Gradually

Do NOT adjust all stands aggressively at once.

Adjust:

• 1–3 stands at a time
• Re-run sample panel
• Measure
• Then proceed

Controlled calibration prevents scrap spikes.

Entry Section Adjustment

Thickness change affects entry setup.

✔ Side Guides

Thicker material requires:

• Slightly wider guide spacing

• Avoid excessive side pressure

Thinner material:

• Lighter contact

• Avoid edge crushing

✔ Pinch Rolls

Increase pressure for thicker material.
Reduce pressure for thinner material.

Incorrect pinch pressure causes strip slippage or marking.

Shear System Adjustment

Thicker material requires:

• ✔ Blade clearance adjustment
• ✔ Higher hydraulic pressure
• ✔ Slower initial cut speed

Thinner material requires:

• ✔ Reduced blade clearance
• ✔ Lower pressure
• ✔ Inspect burr formation

Incorrect shear clearance causes:

• Excess burr

• Edge deformation

• Blade chipping

Drive System Monitoring

After gauge change:

• ✔ Monitor motor current
• ✔ Listen for vibration
• ✔ Check chain tension
• ✔ Watch bearing temperature

Higher gauge increases drive load.

Current spikes indicate over-compression.

First-Off Panel Inspection (Critical)

Run 3–5 test panels at low speed.

Measure:

• ✔ Panel width
• ✔ Rib height
• ✔ Overall flatness
• ✔ Edge wave
• ✔ Oil canning
• ✔ Length accuracy

Do not increase speed until first-off approved.

Gradual Speed Ramp Procedure

After correct profile achieved:

• ✔ Increase speed gradually
• ✔ Monitor vibration
• ✔ Monitor bearing temperature
• ✔ Check dimensional stability

High-speed immediately after changeover increases wear risk.

Common Thickness Changeover Mistakes

• ❌ Not measuring actual coil thickness
• ❌ Over-tightening roll gap immediately
• ❌ Ignoring tensile strength variation
• ❌ Not adjusting shear clearance
• ❌ Not adjusting pinch roll pressure
• ❌ Skipping first-off inspection
• ❌ Running full speed immediately

Most scrap spikes happen in first 30 minutes after changeover.

Gauge Change Financial Impact

Improper changeover can cause:

• 3–8% scrap for first shift

• Bearing overload damage

• Tool chipping

• 1–2 hours downtime

One poor changeover can cost:

$2,000–$15,000 depending on production volume.

Changeover Time Target

Well-trained teams:

30–60 minutes for simple thickness change
Longer if shear adjustment required

Rushed changeovers increase scrap dramatically.

Documentation Best Practice

Record:

• Coil batch number

• Thickness measured

• Roll gap adjustment reference

• Shear clearance setting

• First-off panel measurements

• Motor current baseline

This builds a repeatable calibration database.

Advanced Best Practice: Create Gauge Setup Charts

For each thickness:

Maintain reference sheet:

• Roll gap bolt position

• Shim combination

• Shear clearance

• Motor current expected range

• Rib height measurement target

Reduces adjustment time dramatically.

Frequently Asked Questions

Do I need to adjust every stand during thickness change?

Usually yes, but gradually and systematically.

Why does thicker material increase bearing failure risk?

Higher forming pressure increases radial load on bearings.

Why does thinner material cause oil canning?

Over-compression and uneven forming amplify stress in thin steel.

Should shear clearance always be adjusted?

Yes when thickness difference is significant.

Can I use same settings for same gauge from different suppliers?

Not always — tensile strength varies.

Final Conclusion

Changing coil thickness in PBR production is a controlled recalibration process — not a quick adjustment.

Done correctly, it:

• Reduces scrap
• Protects tooling
• Extends bearing life
• Maintains quality
• Stabilizes production

Done poorly, it:

• Increases downtime
• Damages equipment
• Destroys profit

In roll forming, controlled gauge change equals mechanical stability — and mechanical stability equals financial stability.