Inkjet / Printer Integration in Roll Forming Machines — Encoder-Based Print Timing Control

Introduction — Why Printing Systems Are Used in Roll Forming

Many roll forming products require identification marks printed directly on the steel strip or finished panels. These markings are used for product identification, traceability, installation guidance, or branding.

Typical information printed on roll formed products includes:

• production date and time
• batch numbers
• product codes
• company logos
• installation marks
• length indicators

To ensure these markings appear in the correct position, the printer must be precisely synchronized with the movement of the strip.

Modern roll forming machines achieve this synchronization through PLC-controlled inkjet printers integrated with encoder-based position tracking.

Types of Printers Used in Roll Forming Lines

Several types of industrial printing systems are used in roll forming machines.

Common printer types include:

Continuous Inkjet Printers (CIJ)

These printers produce a continuous stream of ink droplets and are widely used for high-speed marking.

Advantages:

• suitable for high-speed production
• flexible text printing
• reliable operation.

Thermal Inkjet Printers (TIJ)

Thermal inkjet printers use cartridges similar to office printers but are designed for industrial applications.

Advantages:

• high print resolution
• simple maintenance.

Laser Marking Systems

Laser systems mark the metal surface without ink.

Advantages:

• permanent markings
• no ink consumption.

Most roll forming machines use continuous inkjet printers due to their speed and reliability.

Why Encoder-Based Print Timing Is Required

Because the strip is moving continuously through the machine, printing must occur at a precise position on the material.

If printing is not synchronized with strip movement, several problems may occur:

• incorrect marking position
• inconsistent spacing between marks
• unreadable product information.

To avoid these problems, the PLC uses encoder feedback to determine exactly when to trigger the printer.

Encoder-Based Position Tracking

An encoder measures the movement of the strip as it travels through the roll forming machine.

Encoders are typically mounted on:

• measuring wheels contacting the strip
• main drive shafts
• gearbox output shafts.

As the strip moves, the encoder generates electrical pulses.

The PLC counts these pulses to determine the exact strip position.

This position information allows the PLC to trigger the printer at the correct moment.

Printer Trigger Signals

Most industrial inkjet printers accept an external trigger signal.

This signal tells the printer when to print.

The PLC generates this trigger signal based on encoder position.

Typical trigger methods include:

• digital output pulse from the PLC
• encoder signal pass-through
• communication-based print commands.

The printer receives the trigger signal and prints the programmed message.

Print Offset Adjustment

The printer is usually mounted some distance upstream from the cutting station.

Because of this distance, the PLC must compensate for the strip travel distance between the printer and the final product location.

This distance is called the print offset.

The PLC calculates the correct print trigger position by subtracting the offset from the target print location.

This ensures the printed information appears in the correct position on the finished panel.

Print Pattern Programming

Printing systems often support multiple print patterns.

Examples include:

• one print per panel
• repeated markings along the strip
• serial number printing
• installation marks at specific intervals.

The PLC may control these patterns using encoder position data.

For example:

• print every 1 meter
• print once per panel
• print after each punch operation.

These patterns are usually stored in the machine recipe system.

Integration with Cut-to-Length Systems

Printer timing must also coordinate with the cut-to-length system.

For example:

If a panel length is 6 meters and the printer must mark the panel center, the PLC calculates the encoder position where printing should occur.

This ensures the mark appears in the correct location on the finished panel.

Proper integration between printing and cutting systems ensures accurate product labeling.

PLC Control Logic for Printing

A typical PLC printing sequence includes several steps.

Step 1 — Encoder Monitoring

The PLC continuously counts encoder pulses to track strip movement.

Step 2 — Print Position Calculation

The PLC determines when the strip approaches the programmed print position.

Step 3 — Print Window Verification

The PLC confirms that the strip is within the allowed print window.

Step 4 — Trigger Output

The PLC sends a digital trigger signal to the printer.

Step 5 — Printer Confirmation

Some printers send a feedback signal confirming that the print command was executed.

Printer Communication Integration

Some modern printers communicate with the PLC using industrial communication networks.

Common communication methods include:

• Ethernet communication
• serial communication
• industrial protocols.

This allows the PLC to send messages such as:

• print content updates
• serial number data
• batch numbers.

This integration improves automation and traceability.

Synchronization with Line Speed

Printing must remain synchronized with the machine speed.

If line speed changes, the PLC automatically adjusts the print trigger timing.

Because encoder feedback tracks strip movement directly, print accuracy remains consistent at different speeds.

Print Quality Considerations

Several factors influence print quality in roll forming environments.

These include:

• strip surface condition
• ink type
• printer distance from the strip
• line speed.

Proper printer mounting and ink selection improve print readability.

Common Printer Integration Problems

Several problems may occur in printing systems.

Print Position Errors

Incorrect print positions may occur if:

• encoder calibration is incorrect
• print offset values are wrong.

Missed Print Triggers

Missed prints may occur if:

• PLC output signals fail
• printer trigger settings are incorrect.

Blurred or Smudged Printing

Poor print quality may occur if:

• ink is incompatible with the material surface
• printer distance from the strip is incorrect.

Troubleshooting Printer Systems

Technicians diagnosing printing issues should check:

• encoder pulse signals
• PLC trigger outputs
• printer trigger configuration
• print offset settings.

Observing encoder position values during production helps identify timing problems.

Commissioning Printer Integration

Commissioning printing systems involves several steps.

Typical commissioning tasks include:

1 verifying encoder scaling
2 configuring print trigger signals
3 calibrating print offset distance
4 testing print accuracy at multiple speeds.

Multiple test panels should be produced to confirm correct marking.

Preventative Maintenance for Inkjet Printers

Routine maintenance improves printer reliability.

Recommended maintenance includes:

Daily checks:

• clean printer nozzles
• verify ink levels.

Weekly inspections:

• check printer alignment
• inspect print quality.

Regular maintenance prevents printing failures.

Benefits of Printer Integration in Roll Forming

Printer integration provides several advantages.

These include:

• improved product traceability
• easier product identification
• automated marking
• reduced manual labeling.

Printing automation is increasingly important for modern manufacturing operations.

FAQ — Inkjet Printer Integration

Why are printers used in roll forming machines?

Printers mark panels with identification information such as product codes, dates, or installation marks.

How does the PLC know when to trigger the printer?

The PLC uses encoder feedback to determine the strip position and sends a trigger signal at the correct location.

What is print offset?

Print offset is the distance between the printer location and the desired marking position on the finished panel.

Can printers mark every panel automatically?

Yes. The PLC can trigger the printer once per panel using encoder-based length measurement.

Why do printers sometimes miss marks?

Missed prints may occur due to incorrect trigger signals, printer configuration errors, or encoder faults.

Can the PLC change printed information automatically?

Yes. Modern printers allow the PLC to send updated messages such as serial numbers or batch data.