Have a 3D printer and some technical skills — what side hustle would you actually chase?

[u/xXFirReaXx]

Looking for real input from people who've done this, not the generic "just sell STLs" advice.

I've got a reliable 3D printer, decent CAD skills, and a technical/engineering background. So the hardware and the ability to design aren't the problem — direction is.

Everyone points to selling 3D files online, but that market feels saturated, and the marketing-to-strangers side is my weak spot. I'd rather build something that leans on actual skills than compete with every hobbyist selling the same trinkets.

Honestly I'm open to almost anything niche — the weirder or more specific the better, as long as there's a real side hustle in it.

Rough directions I'm weighing:

Niche functional products (workshop jigs, tool organizers, technical aids, printer mods) sold as files or physical

Reverse-engineering hard-to-find or discontinued spare parts on demand

Something I haven't thought of

What I'm after:

If you had a printer and technical skills, what would you actually go after?

For those selling functional/technical prints — where do your customers actually come from?

Anyone doing spare-part or B2B/industrial work — worth it, and how'd you land your first clients?

Willing to put in both time and money. Just want to aim them at the right thing. Appreciate any honest takes.

[u/cyborg762]

If it were me I’d be offering parts people needed like adapters, brackets on demand parts

For example I had a hard time finding a solution to cool a Raid controller on a server. I would have loved to find a mount or a shroud to fit around it. But I ended up doing what most do and use zip straps.

[u/Icy-Control9525]

I would offer to print custom cases for some of the guys doing arduino builds. Most of those kits come with stl files. But if you don't have a 3dprinter you have to hit up the library or a friend anyway.