engraving keycaps, then fill with paint

[rvr1982]

Greetings,

I'm about to make a few tests with a CNC milling machine and a bunch of blanck pbt keycaps from Aliexpress.
My plan is to engrave the top faces (and maybe front faces for F1-F12) to make my own layout, then to fill the engraved letters with paint. (is this what's called etching?) I will use a 0.5mm end mill.

What do you think would be the most appropriate paint to use for this process ? Acrylic paint ?
How would you apply it to the keycaps, and which solvent would you use to clean any excess paint without harming the keycaps ? I have WD40, isopropyl alcohol, and acetone lying around in the basement.

Maybe there's someone here who tried this before, and has a few ideas ? Maybe there's a tutorial out there, which i did not find yet ?

Thanks in advance for any tips and tricks, and best regards

[nevin]

acrylic, enamel, or nail polish (enamel)

when doing infill, there are a handful of ways to get the finished result.
- infill (thicker) & sand back to surface - provides the smoothest transition between cap & infill. don't use acrylic for this method (even when cured it's too soft), and make sure the enamel is well cured & hard before sanding.
- infill just to surface & wipe away excess - kinda like antiquing or weathering that the paint only stays in the recesses. acrylic is probably best for this method (easier to clean up excess).
- if you do decide to use some kind of thinner to clean up the excess paint, test on a spare cap first! acetone will melt abs as well as a bunch of other plastics. alcohol is not strong enough to cut most paints especially after fully cured. WD40 is a petroleum base lubricant and will probably react badly with most plastics over time (doesn't happen immediately). if you're looking for an intermediate cleaner, believe it or not, try lighter fluid. it's not very aggressive but should have enough oomph to get light streaks off. i've used lighter fluid to clean sticker residue off all kinds of materials for years with no adverse effects. again, test on a spare first!

[rvr1982]

Great feedback!
I will avoid the sandpaper & enamel solution, i'm too afraid it might damage the grainy texture of the keycaps. I'll try acrylic, with lighter fluid which should not be too difficult to find.
Thanks for all the information 

[nevin]

well. acrylic is waterbased, so lighter fluid is not necessary. just clean it up before it's totally dry, or scrape/peel once dry.

[rvr1982]

I forgot one stupid detail : it's the first time I'm engraving pbt. The result is not what i expected. All tools i tried left me with some impossible to remove residues inside of the engraving.

(first cap after sanding, second cap without doing anything, third cap after removing the residue with cutter and tweezers, and last one same as third, with paint)
I thought it would be much easier... I ordered a few different tools to make more tests.
One thing I'm happy with : acrylic paint. So easy to use. The excess is easily removed with a wet towel before drying, and after drying a little bit alcohol helps to make it look clean.
Black on white is a little bit dark though, I'll get some shades of grey for the next test.

[nevin]

As long as the tools are sharp, what about slowing down the rpm?

I've used dremels on various plastics for years & if it was spinning too fast it would melt the plastic as the blade passed through it, leaving a ragged trail behind it.

[xack]

Hehe you are exactly where i was when attempting the same thing 

I also tried engraving PBT but that did not work to well, regardless of tool, feeds and speeds.
I even tried to put the caps in the freezer before carving xD
That is why i finally settled to imagine a new methode.

https://www.youtube.com/watch?v=JR1BwcFyexQ
https://geekhack.org/index.php?topic=96010.0

I don't know if there is a tool that would work better than those i tested but who knows.

[Latham296]

The first step was converting it to USB. He’s using a Teensy 2.0 mostly because it is super inexpensive, and its able to act as a USB HID device. In addition to wiring up the keyboard to the Teensy he’s also added foot pedals that connect via 1/8″ stereo plugs mypremiercreditcard

[Leslieann]

Due to it's pretty low temp, I'm not sure you're going to get good results without coolant.

Best method I've seen was using a laser to burn laserjet toner into the cap.

[Nixon]

Xack's method is great. Tried it with nail art pigment too and that works really well, even on ABS translucent caps. (Though be careful lasering ABS at the fumes aren't super healthy.)

https://www.reddit.com/r/MechanicalKeyboards/comments/a1skv5/laser_engraving_keycaps_with_nail_art_pigment/