Study of Laser Engraving Anodized Aluminium

Pictures to be added once I figure out how to get zoomed pics…

Question: what type of anodizing?

A. 0-100%, 5% Steps, 100% Speed, 100% Power, 500DPI, 500PPI

  • central ring not visible (4 in source, 3 visible.)
  • notice brightness of white starts to decrease after ~55% power; no longer “opening” the anodizing, starting to ablate it!

B. 0-50%, 2.5% Steps, 100% Speed, 100% Power, 500DPI, 500PPI

  • central ring not visible (4 in source, 3 visible.)
  • notice brightness of white starts to decrease after ~55% power; no longer “opening” the anodizing, starting to ablate it!

C. 30-50%, 5% Steps, 100% Speed, 100% Power, 500DPI, 500PPI

D. 45-65%, 5% Steps, 100% Speed, 100% Power, 500DPI, 500PPI

E. 45-65%, 5% Steps, 100% Speed, 100% Power, 1000DPI, 500PPI

  • notice no “interleaving” between engraving lines
  • more energy/area -> anodizing is ablated at lower powers!

F. 45-65%, 5% Steps, 100% Speed, 100% Power, 500DPI, 500PPI, 0.5mm Out of Focus

  • energy is spread out, smoother, but slightly higher power required

G. 45-65%, 5% Steps, 100% Speed, 100% Power, 500DPI, 500PPI, 1mm Out of Focus

  • energy is more spread out, smoother, but slightly higher power required

Further Info

The PPI (Pulses Per Inch) setting could (should) have been set to 1000PPI for the 1000DPI case. DPI and PPI should always be multiples of each other to avoid aliasing, and usually are set to match. In this case the goal was to avoid changing more than one variable at a time. And I forgot :wink:.

Post Engraving Re-Colouring & Sealing

Google searches shows that some people are taking advantage of laser engraving to create very finely detailed secondary coloured anodizations, mostly using water based dye markers- and then sealing. Information for water sealing: https://aluminumsurface.blogspot.com/2009/04/why-sealing-process-is-so-important.html?m=0, https://core.ac.uk/download/pdf/294780012.pdf.

A sharpie test was done on the provided samples. Marks with a sharpie were made on the un-engraved anodized aluminium, freshly engraved, and an engraved dot from the manufacturer.

The marks wiped off with IPA for both the anodized area and manufacturer engraved dot.

The marks did not clean off from the engraved area.

Then engraved test parts were boiled in distilled water for roughly an hour, and then marked with a sharpie. IPA cleaned these areas only a little better than the non-sealed, but not significantly.

On closer inspection the samples with the dot from the manufacturer look a little different and may have a different anodization process applied.

The DI sealing also slightly changed the colour and lustre of the anodizing. The engraved area feels slightly smoother.

Question: Are some engravings done before the final sealing process?