Marking on the fly is a synchronisation problem wearing a laser costume

The optics are the easy part. Keeping the scan field, the encoder signal and a moving product in agreement at line speed is where installations succeed or fail.

By LasersNews Desk·23 Jul 2026·2 min read

Detailed view of an industrial laser engraving machine in action, highlighting precision equipment. — Photo by Opt Lasers from Poland on Pexels

Marking a stationary part is a solved problem. Marking a part moving past on a conveyor at production speed introduces a set of issues that have very little to do with lasers and a great deal to do with motion control.

The basic mechanism

The scanner compensates for product motion by adding a velocity term to its deflection, so the beam tracks the part while drawing the mark. That requires the controller to know the product's position continuously, which comes from an encoder on the conveyor rather than from an assumed line speed.

Assuming constant speed is the classic error. Conveyors accelerate, decelerate, and slip. A mark drawn against an assumed speed skews or stretches when the real speed differs, and the distortion appears in a way that is easy to blame on the laser.

Trigger and latency

A product sensor triggers the mark, but between trigger and first pulse there is latency: sensor response, controller processing, scanner settling. At 60 metres per minute the product moves a millimetre per millisecond, so latency turns directly into position error.

Practical installations characterise and compensate that latency rather than tuning the sensor position by trial and error, because the latency changes with mark content and controller load.

Field geometry

The scan field is not flat and not distortion-free, and a mark drawn while the part crosses the field uses different parts of that field for different characters. Field correction that is adequate for static marking may not be adequate on the fly, and correction files usually need to be generated for the specific lens and working distance.

What determines success

Installations that work generally share three things: an encoder mounted where it actually measures product motion rather than motor rotation, characterised and compensated trigger latency, and a mark content budget that fits within the available field crossing time.

Installations that fail usually fail on the first of those. A conveyor with belt slip between the drive and the product makes the encoder signal a description of the motor rather than of the product, and no amount of laser parameter tuning fixes it.

This article was produced by the LasersNews AI desk and reviewed by our editors.