One thing we teach in the laser authorization course at my hackerspace is that the laser will remove the anodization from aluminum.
The laser won't touch the aluminum metal, or any metal in general(*), but etching away the anodization is sometimes useful when you want to put your logo on a finished project, or for front panel markings.
The process does not remove *all* of the anodized layer, so the end result is a slightly tinted aluminum against the anodized background. In other words, the process does not result in perfect contrast of the image against the anodized background.
Still, it's something you can do with the laser that will give your project a professional, polished look.
You can purchase anodized aluminum plate (and many other forms) on eBay.
(*) This is not strictly true, but it's against house rules to try, so we tell people that the laser won't do it.
Christmas for Frankie
So when my grand-niece had her water bottle stolen and her mom suggested I get her a new one for Christmas, I made personalized versions. The results are shown up top.
She's studying genetics doing research on viruses and fruit flies, so one bottle has a virus capsid, one bottle has fruit flies (which doesn't photograph very well), and one bottle has Alice and the caterpillar.
Each has her name engraved along the bottom, so they're less likely to be stolen.
[HA! I just now figured out how to make Hackaday.io break paragraphs at the image boundary. Take *that*, Hackaday!]
Speed and Power
Scan speed is 350mm/s, scangap is 0.15mm which is about 3 scans per line with our laser's 0.5mm line width.
Remember to turn OFF bi-directional scanning to avoid any backlash in scan positioning. Turn ON bi-directional, and the left scans will be offset from the right scans by backlash in the mechanical system, making edges look like saw teeth. Probably not what you want.
The power reading of 50% for our aging 80-watt laser probably translates to about 25 watts(*), convert as needed for your system.
(*) Our unit mins out at about 25% due to the age of the tube.
Positive and Negative
Be careful with the positive- and negative-ness of the image. The "Alice in Wonderland" image is originally black on a white background, but the etching removes the darker anodization to reveal the brighter aluminum.
The Alice scene thus became a sort of "X-ray" version - I should probably invert the image and make another one, but I ran out of bottles.
The accuracy of engraving is pretty good, considering the spot size of our laser is .02" to begin with. The line on the right is freehand from the image; ie - it's not a computer-drawn straight line.
The aluminum metal has a slight bluish (left) or greenish (right) tinge from leftover anodization, because the engrave process doesn't remove everything.
It would be interesting to see how the anodized/etched sections respond to chemical etching. Chemical etching might be an interesting hobbyist way to make complex thin aluminum pieces using a laser cutter.