The official procedure with the machine's gauge is the right starting point. This is how to verify it, which matters because focus is the number one cause of "my engraving looks weak".
Focus ramp test
- Prop a strip of scrap at a shallow angle — one end a few millimetres closer to the lens than the other.
- Engrave a single thin line at low power along the length.
- Find where the line is thinnest and darkest. That is your true focal point.
- Measure the material height at that point and compare with what the gauge gives you.
Within 0.3mm, trust the gauge. Further out, something is off: bed not level, module mount loose, or a bowed sheet.
Things that quietly change your focus
- Material thickness varying batch to batch (plywood is rarely exactly 3mm)
- Riven or reclaimed material with high and low spots
- A honeycomb bed or riser base that has shifted
- Module mounting bolts settling after a few hundred hours
Keep the test piece
Re-run the same ramp on the same material in a few months. If the line is wider or fainter at the same settings, you're looking at a dirty lens or a tired module rather than a focus problem.
LaserPecker publish their own documentation on this topic — worth reading alongside these community notes.
Official article