Coil End Detection & Scrap Handling Logic in Roll Forming Machines — PLC Control & Automation

Introduction — Why Coil End Detection Matters in Roll Forming

Roll forming machines process steel coil continuously until the coil is completely consumed. When the coil reaches its end, the machine must detect the remaining strip and stop production safely.

If the coil end is not detected correctly, several problems may occur:

• damaged tooling
• incorrect panel lengths
• strip jams in the machine
• scrap entering finished stacks

To prevent these issues, roll forming machines use coil end detection systems integrated into the PLC control logic.

The PLC uses sensors and encoder tracking to detect when the coil is nearly finished and then manages the remaining scrap material.

Proper coil end detection improves machine safety and reduces material waste.

What Is Coil End Detection?

Coil end detection is the process of identifying when the steel strip from a coil is about to run out.

Once the PLC detects the coil end, it prepares the machine for shutdown or scrap handling.

Coil end detection usually occurs before the strip completely leaves the uncoiler.

This allows the PLC enough time to manage the final strip section.

Sensors Used for Coil End Detection

Several types of sensors may be used to detect the end of the coil.

Common sensor types include:

Photoelectric Sensors

These sensors detect the presence or absence of strip material.

They are often installed near the entry section of the machine.

Loop Sensors

Loop sensors detect when the strip loop between the uncoiler and roll former disappears.

When the loop collapses, the PLC interprets this as a coil end condition.

Proximity Sensors

Proximity sensors may detect the metal strip passing a certain point.

When the strip no longer triggers the sensor, the PLC detects coil depletion.

PLC Coil End Detection Logic

The PLC continuously monitors sensors in the entry section of the machine.

A typical detection sequence includes:

1. strip presence detected by entry sensor
2. strip continues feeding through machine
3. strip presence signal disappears
4. PLC identifies coil end condition.

Once the coil end is detected, the PLC triggers the scrap handling sequence.

Remaining Strip Length in the Machine

Even after the coil end is detected, there is still a section of strip inside the machine.

This strip may include:

• material between the uncoiler and roll former
• material inside forming stands
• material between forming stands and shear.

The PLC must allow this remaining strip to pass through the machine before stopping production.

Scrap Handling Logic

The final section of strip is usually considered scrap because it cannot form a complete product.

The PLC must prevent this scrap from entering the finished panel stack.

Scrap handling systems may include:

• scrap chutes
• scrap diverters
• manual scrap removal areas.

The PLC controls these systems to direct scrap away from the finished product stack.

Scrap Diverter Control

Some roll forming machines include scrap diverters near the run-out table.

These mechanisms redirect scrap material away from the stacking system.

The PLC activates the diverter when the scrap section reaches the end of the machine.

This prevents scrap from mixing with finished panels.

Shear Control During Coil End

During coil end conditions, the PLC may perform several cutting operations.

Typical actions include:

• cutting the final usable panel
• cutting the scrap section
• stopping the machine after scrap discharge.

These cuts ensure that only usable panels reach the stacker.

Operator Alerts for Coil End

When the PLC detects the coil end, it usually alerts the operator through the HMI.

Typical messages include:

• coil end approaching
• prepare new coil
• scrap section processing.

These alerts help operators prepare the next coil.

Integration with Coil Changeover

In some roll forming lines, coil end detection triggers coil changeover procedures.

This may include:

• stopping the machine
• preparing the uncoiler for the next coil
• threading the new strip.

Advanced lines may support automatic coil joining or welding systems.

PLC Coil End Sequence

A typical coil end handling sequence includes several stages.

Stage 1 — Coil End Detection

The entry sensor no longer detects strip material.

The PLC identifies the coil end.

Stage 2 — Remaining Strip Processing

The machine continues running until the remaining strip passes through the forming section.

Stage 3 — Scrap Identification

The PLC determines when the scrap section reaches the shear or stacker.

Stage 4 — Scrap Diversion

The scrap diverter activates to redirect scrap material.

Stage 5 — Machine Stop

Once the scrap section exits the machine, the PLC stops production.

Safety Considerations

Coil end handling must be carefully controlled to prevent machine damage.

Potential hazards include:

• strip whipping
• strip misalignment
• uncontrolled scrap movement.

The PLC ensures that the machine slows down or stops safely when coil end conditions occur.

Common Coil End Detection Problems

Several problems may occur in coil end detection systems.

False Coil End Detection

False detection may occur if sensors are misaligned or contaminated.

This may cause the machine to stop unexpectedly.

Missed Coil End Detection

If sensors fail to detect the coil end, scrap material may pass through the machine.

This can damage tooling or produce defective panels.

Scrap Entering the Stacker

If the scrap diverter fails to activate, scrap panels may be mixed with finished panels.

Troubleshooting Coil End Systems

Technicians troubleshooting coil end detection should check:

• strip presence sensors
• PLC detection logic
• scrap diverter mechanisms
• encoder position tracking.

Monitoring PLC input signals during operation helps identify detection errors.

Commissioning Coil End Detection Systems

Commissioning coil end detection systems requires careful testing.

Typical commissioning tasks include:

1 verifying sensor alignment
2 testing detection signals
3 testing scrap diversion systems
4 verifying machine shutdown logic.

Test runs should simulate coil end conditions to verify proper system behavior.

Preventative Maintenance for Coil End Systems

Routine maintenance improves detection reliability.

Recommended inspections include:

Monthly checks:

• clean photoelectric sensors
• verify sensor alignment.

Quarterly inspections:

• inspect scrap diverter mechanisms
• test PLC detection logic.

Proper maintenance reduces detection failures.

Benefits of Reliable Coil End Detection

Effective coil end detection systems provide several advantages.

These include:

• reduced material waste
• improved product quality
• safer machine operation
• smoother coil changeovers.

These benefits help maintain efficient roll forming production.

FAQ — Coil End Detection & Scrap Handling

How does a roll forming machine detect coil end?

Sensors detect when strip material is no longer present in the entry section of the machine.

Why is scrap generated at the end of a coil?

The final section of strip cannot form a complete panel and is usually discarded.

What happens when the PLC detects coil end?

The PLC processes the remaining strip, diverts scrap, and then stops the machine.

What is a scrap diverter?

A scrap diverter redirects scrap material away from the finished product stack.

Can coil end detection prevent machine damage?

Yes. Early detection prevents scrap material from entering forming stands or stacking systems.

How can coil end detection errors be prevented?

Regular sensor maintenance and correct PLC logic configuration help prevent detection errors.