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Reference & ToolsModule 7.3~4 min read

Failure Diagnostics

Visual symptoms paired with root causes and fixes. Bookmark this page, when something goes wrong mid-shift, you scan symptoms here, find the diagnosis, and you're back to work.

Black mark looks brown / purple instead of pure black

Symptom: Engraved area has a copper-brown or purple-violet tint, especially noticeable in daylight. Looks fine under shop fluorescents.

  • Cause 1, Insufficient defocus. Black-on-stainless wants +1.5 to +4 mm of defocus. Too close to focus = oxide layer too thin = wrong color reflection.
  • Cause 2, Speed too slow OR power too high. Both deposit too much energy.
  • Cause 3, Frequency wrong. Should be 35-60 kHz with 2 ns pulse.
  • Fix: Increase defocus first. If still tinted. Drop power 5%. Re-test.

Color anneal won't repeat: different cards every time

  • Cause 1, Surface contamination. Fingerprint oil and shop dust contaminate the oxide reaction. Wipe with reagent IPA every time.
  • Cause 2, Different alloy lots. "304 stainless" varies wildly. New supplier? New test card.
  • Cause 3, Z drift. Re-verify focus before each color run.
  • Cause 4, Temperature. Cold parts in winter need slightly different settings than warm parts in summer. Yes, really.

Banding: visible horizontal stripes in a fill

  • Cause: Line interval too wide. Each hatch line shows because there's a gap of bare metal between them.
  • Fix: Tighten line interval before raising power. Try 0.01mm if you were at 0.02. Or rotate scan angle 7° per pass.

Edge "comma" / overshoot artifacts on fills

Symptom: Filled rectangles have small dot-and-flick marks just outside their edges, like the laser fired before the mirrors stopped.

  • Cause: Laser On TC too short (galvo) or Overscanning too low (gantry). Beam fired before mirrors finished decelerating.
  • Fix: Increase Laser On TC by 50 µs increments. On gantry, increase Overscanning %.

Mark is weak / barely visible

  • 90% case: focus is wrong. Re-check Z. Use focus stick.
  • Lens is dirty. Inspect under flashlight.
  • Power scaled down accidentally: check layer settings.
  • Wrong lens loaded vs. correction file: verify device profile matches the physical lens.
  • Below cutoff frequency: at 20 kHz on a JPT MOPA you're getting derated power. Try 48-60 kHz.

Mark is too aggressive / burning through

  • Defocus too low, raise Z.
  • Speed too low.
  • Frequency too high, driving too much energy into the same spot.
  • Wrong lens (using 70mm where settings were for 150mm = much higher power density).

Photo engrave is muddy / lacks contrast

  • Cause 1, Source image levels not stretched. Open in Photoshop, run Levels, anchor pure black and pure white.
  • Cause 2, Wrong dither. Use Jarvis or Stucki for portraits, not "Dither" (Floyd-Steinberg).
  • Cause 3, DPI too low. Aim for 1016 DPI (0.025 mm) on metal photos.
  • Cause 4, Surface too reflective. Brushed stainless reads photos better than mirror polish.

Coin relief looks flat: no real depth

  • Cause 1, Wrong image mode. Must be 3D Sliced for relief, not Grayscale or Threshold.
  • Cause 2, Depth map has too much middle gray. Run through SculptOK or stretch tonal range manually. Full black ↔ full white.
  • Cause 3, Not enough passes. Brass coins need 200+ passes at the prescribed settings to develop real depth.
  • Cause 4, Cleanup pass disabled. Vaporized debris reflects subsequent passes; turn cleanup on.

Distortion: square comes out trapezoid

  • Cause: Wrong correction file for the lens, or lens calibration drifted.
  • Fix: Verify the right .cor file is loaded for the active lens. Re-run Lens Correction Wizard if needed.

Red dot doesn't match where the laser fires

  • Cause 1, Z is wrong. Red dots converge at focus. Check Z first.
  • Cause 2, Alignment drifted. Run Tools → Galvo Lens Calibration → Alignment Wizard.

Galvo won't connect in Lightburn

  • USB cable swap (cheap cables fail).
  • Driver: ensure JCZ/BJJCZ driver installed. Check Device Manager.
  • Power-cycle the laser before opening Lightburn.
  • Try a different USB port, front-panel USB ports on PCs are often noisy.

Glock frame stipple has glossy melted patches

  • Cause: Power too high or speed too low. Polymer melted instead of foaming.
  • Fix: Drop power 5% and increase speed by 200 mm/s. Re-test on the inside of the magwell.
  • Damage: melted patches can be patched with epoxy + re-stippled, but never look identical to virgin polymer.

Anodized AL mark is gray instead of bright white

  • Cause: Burning through the anodize layer into bare aluminum.
  • Fix: Drop power 5%. Anodize is ~25 µm thick, short pulses (8-15 ns) at modest power evaporate just the dye without touching the aluminum.

Acrylic edge is matte / fogged (CO2)

  • Cause 1, Air assist too high. High air kills the flame-polish effect. Drop pressure.
  • Cause 2, Wrong acrylic. Extruded looks matte; switch to cast.

Lightburn time estimate is wildly off

  • Cause: Galvo TC delays not matching reality.
  • Fix: Run a small known job, time it manually, compare. If real time is 30%+ longer than estimate, the TC values in your device profile are too aggressive, increase Laser Off TC and End TC by 50 µs each.