settings · metal · engraving
Anodized Aluminum Engraving Settings (5W–40W Diode Lasers)
On a 20W diode laser, engrave anodized aluminum at 30% power, 4,500 mm/min, 1 pass, 254 DPI. The laser ablates the thin anodized oxide layer, revealing the bright bare aluminum underneath — producing a contrasting silver mark on the colored surface. This is not "engraving" in the deep-cut sense; the mark depth is 0.01–0.05mm. Anchored on Sculpfun S30 Pro Max 20W official data; other wattages normalized via the Laser Tinkerer Energy Index.
- EI target: 0.024 J/mm — very low, because the anodized layer is only 10–25µm thick
- The result is bright silver on colored anodized background — not a dark mark as with wood
- Black and dark anodized aluminum are the easiest to mark clearly (highest contrast)
- Bare aluminum (unanodized) reflects 450nm light and cannot be engraved without marking spray or dry moly lubricant
What happens to anodized aluminum under a diode laser
Anodized aluminum has a thin aluminum oxide (Al₂O₃) layer on its surface, typically colored with dye. This oxide layer absorbs the 450nm diode beam and vaporizes, removing the dye and exposing the bare aluminum metal beneath. The result is a bright, shiny, permanent mark with a metallic appearance. The mark does not corrode — the bare aluminum surface oxidizes naturally into an invisible Al₂O₃ passivation layer within hours of exposure to air.
Engraving settings by wattage
| machine class | speed (mm/min · mm/s) | power | passes | EI (J/mm) | source |
|---|---|---|---|---|---|
| 5W | 1,100 · 18.3 | 30% | 1 | 0.024 | |
| 10W | 2,250 · 37.5 | 30% | 1 | 0.024 | |
| 20W ★ | 4,500 · 75.0 | 30% | 1 | 0.024 | Sculpfun S30 Pro Max 20W guide |
| 33W | 4,500 · 75.0 | 18% | 1 | 0.024 | |
| 40W | 4,500 · 75.0 | 15% | 1 | 0.024 |
Bare / unanodized aluminum
Bare aluminum metal reflects 450nm blue laser light — the reflectivity is approximately 90% at this wavelength. A diode laser beam bouncing off bare aluminum is an eye hazard and produces no useful mark. Two solutions:
- Marking compound. Apply Cermark LMM6000, Brilliance Laser Ink, or dry moly lubricant (Molykote 321) to the surface. After laser engraving, the compound fuses to the metal surface, leaving a permanent black mark. Wipe off the residue after. This works on bare aluminum, stainless steel, and titanium.
- Anodize the aluminum first. A home Type II sulfuric acid anodizing kit produces an anodized layer on bare aluminum blanks. After anodizing and dyeing, the material is ready for laser engraving as described in the table above.
reflectivity hazard
Never run a diode laser on bare, polished, or mirror-finish aluminum without a marking compound. The reflected beam can exit your machine's work area at full power and cause permanent eye damage even at indirect-reflection distances. Use a matte-finish or marking-spray-coated surface.
FAQ
Does anodizing color affect the settings? Yes, moderately. Black anodized aluminum has the highest absorptivity and marks most easily. Light-colored or clear-anodized aluminum reflects more of the beam — you may need to reduce speed by 10–15% or increase power by 5% for lighter anodized colors.
Is the mark durable? Yes. The ablated area exposes base aluminum, which immediately oxidizes naturally to a thin, hard Al₂O₃ passivation layer. The mark is essentially permanent — dishwasher-safe, won't rub off, doesn't fade in sunlight.
Can I engrave titanium the same way? Only anodized titanium works the same way. Bare titanium does not reflect 450nm light as efficiently as aluminum — it is grey, not mirror-finish — and marking compounds work on bare titanium. But anodized titanium behaves similarly to anodized aluminum for ablation.
- Anodized aluminum blanks — black anodized marks most cleanly; look for blanks marketed for laser engraving
- Laser marking spray (for bare metal) — required if working with non-anodized aluminum or other metals
- OD7+ laser safety glasses (450 nm) — especially important with reflective metal surfaces; reflected beams are a real hazard
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