LEGO bricks with alphabet are weirdly unavailable in the 1×1 square size. There are DUPLO bricks and small round pieces with letters, but each with only one letter. Doing it that way needs a pretty big bunch of bricks to actually be able to spell something.

Petteri Aimonen decided to make 1×1 bricks that have one letter on each side. This way one needs only one quarter the size of inventory of bricks on average.

To engrave the bricks, a K40 laser cutter at the local hackerspace was used. The settings were 1000 mm/min speed and the smallest power the tube would run at.

An alignment guide made it easy to place a stack of 10 bricks for engraving.

The CO2 laser just melts the ABS and does not give much contrast in the markings. To make them more visible, I used a pen to color in the grooves. Excess ink can then be wiped out, leaving a well-defined letter.

Initially I tried an alcohol-based permanent marker. Unfortunately the alcohol caused tiny cracks in the ABS plastic, and the ink seeped into them. A water-based gel ballpoint pen worked much better, and after drying the marking seems durable enough.

Read more in the post here along with a link to an Inkscape template.