Laser Etch + Acrylic Backfill finish

[culturejam]

Dave (pickdropper) sometimes does this kind of finish, but he has the big-boy laser and lots of attention to detail. I have neither, haha. But this is a lazy-man's pickdropper fancy finish technique. 

Used a really cheap hobby laser engraver to cut through enough powdercoat to squeegee some acrylic paint in there. The software sucks and alignment is dodgy, but for DIY it's not a bad option.

For this first test, I just did a single pass at max power (3.5W) to see how it would work. Used a toothbrush to clear the ash, wiped it down, and then dabbed some white acrylic paint at the top. Used an old credit card as a squeegee to pull the paint downward and into the crevices to fill. Sort of like silkscreen work.

I let it dry and then wiped gently with 90% isopropyl to clean up the residual paint. It's not amazing, but I'll take it for a first try. The alignment is obviously off-center, but it's close enough that I can still build it. I think I figured out a way to print a template to verify alignment better, but I'll test that later.

Circuit details: It's the DIY classic Bazz Fuss circuit with some fun tweaks. Instead of an integrated darlington transistor (usually MPSA13), I did a discreet darlington with two germanium transistors (for mojo). I used the 2n211, which is a low-gain NPN germanium transistor available from SmallBear Electronics. It's a weird package shape, so I made my own part in Eagle CAD because nobody has a footprint available. I also added a gain control pot and a toggle switch to select between standard silicon and schottky diodes.

Sounds pretty good to me, but I love the base circuit. Adding in germanium mojo and some mods for flexibility is just icing on the tonal cake. I have a few boards left if anybody wants one to mess around with.

[jimilee]

I think it looks really good.


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[matmosphere]

Wow, I'm really digging that look. I've been working on using the 3d printer for finishing enclosures a bit, but that is way nicer looking.

Care to share some info on the laser?

[PapaKev]

I like it! Nice job.

[culturejam]

Care to share some info on the laser?

It's a variation of this one: https://www.amazon.com/Engraver-Engraving-Machine-Printer-7-6X7-6CM/dp/B07N2PP3LG/ref=sr_1_2?dchild=1&keywords=laser+engraver&qid=1610600996&sr=8-2

If you look on AliExpress, you can find that same hardware with different laser heads on it (various wattages). There are some good things about it and some bad things, but it's pretty cheap and it's strong enough to etch away enough of the powdercoat to be useful. It's also quite precise when doing multiple passes.

[pickdropper]

If you get some 3cc syringes and some glue dispensing tips, it's easier.

A microscope helps, too.  ;-)

[culturejam]

If you get some 3cc syringes and some glue dispensing tips, it's easier.

I got some syringes with flat tips (not sharp), but the are hard to use, especially with an etch this shallow.

[gordo]

I'd be quite pleased with that, I like it.

The flat tipped needles on syringes are for glue dispensing (specifically fiber optics and epoxy) or patients that are real assholes...

[cooder]

Looking great really! Nice one!

...or patients that are real assholes...

Spilling my coffee right now...
My wife works in hospital lab and has quotes like that too.

[drezdn]

I like it!

[pickdropper]

If you get some 3cc syringes and some glue dispensing tips, it's easier.

I got some syringes with flat tips (not sharp), but the are hard to use, especially with an etch this shallow.

That's the challenge in general with backfilling laser etches.  It's just so shallow that you need to be really accurate.  You can clean it up a bit by alcohol or by scraping it away, but you need to be careful how you do it.  Myself, I need the microscope to do it accurately.

[culturejam]

Here's another example I did tonight. Different laser engraver than the previous enclosure, but similar wattage (bigger working space and easier to align). This is a Love My Switch blue powdercoat box. I also switched to Light Burn software, which is way more awesome than whatever comes with your cheap Chinese laser. It's free for 30 days, and then it's $40 for a license. I recommend it.

Still needs a bit of cleanup, but it's looking okay. Ignore my fugly drilling at the footswitch, please.

Also, you can see in the upper right parallelogram that I forgot to focus the laser before I started the job. I did a quick pause, got it focused, and resumed. 

[PapaKev]

Nice!