The Symptoms of "Uneven"

Uneven engraving shows as bands across the piece, one side lighter than the other, or blotches that follow the grain. Buyers notice immediately, so it is the first quality problem worth solving. Almost every case traces to one of four causes: bad focus, a dirty lens, uneven speed/power across the bed, or wood that was never flat. This guide gives you a checklist that finds the fault in one job.

1. Focus and Bed Flatness

Most banding is a focus problem. If the material rocks or the bed is not tram, the beam defocuses mid-travel and the mark fades. Use a focus gauge or the paper-Z method at four corners, not one. Place a thin sacrifice board under warped stock so the surface is level. Re-tram the bed if focus varies by more than 1 mm corner to corner. This alone fixes half of "one side is light" complaints.

2. Lens and Mirror Cleanliness

A dusty lens scatters power and drops contrast. Inspect the lens and the first mirror weekly with a bright light; clean with lens tissue and alcohol only, never a rag. A fingerprint on the lens reads as a soft, uneven burn. If cleaning does not lift the contrast, the lens may be pitted from a prior burn — replace it. Keep air assist on so vapor does not recoat the glass during the job.

3. Speed and Power Consistency

If the mark is light at the start and dark at the end, your power supply may be sagging or your acceleration settings are off — add lead-in or slow the corners. Run a ramp test: same art at 5 power steps on one board; the step where the whole field is even is your setting. Avoid maxing power; headroom keeps the tube stable across a long raster.

4. Wood Grain and Moisture

• Soft grain burns dark, hard grain light — that is wood, not the laser; mask and accept it or pick tighter-grain maple.
• Damp stock steams and blotches; store wood dry and let it acclimate a day.
• Knots and resin pockets scorch — rotate the piece or design around them.
• Pre-seal porous wood with a light coat of water or denatured alcohol to even the burn (test first).

A 10-Minute Diagnostic Job

Cut a 100x100 mm square raster of a grayscale ramp at your normal settings. Read it: vertical bands = focus/bed; horizontal fade = power supply; blotches = wood/moisture; soft everywhere = lens. Note the fix and re-run. Within two tests the field should be even.

Frequently Asked Questions

Why is one side always lighter? Focus or bed flatness; re-tram and focus at all four corners.

Cleaning did not help — now what? Lens may be pitted; replace and retest.

Is grain variation fixable? Partly; mask, pick tight grain, or pre-moisten to even the burn.

Run the Ramp Test Tonight

One diagnostic square tells you more than a week of guessing — do it once and uneven engraving stops being your return reason.

If you also evaluate higher-power flatbed cutters for production, compare the HF Laser CO2 cutter range before you decide.