Oooo... 3D printing, my specialty! I have a Prusa MK2, but I have the "MK2.5" upgrade kit in a box, I just haven't gotten around to upgrading it yet.

While the Prusa is expensive, it's hands down the best FDM printer I've used for the money, and I'd say it's better value than far more expensive competitors like the Lulzbot Taz or the Ultimaker machines, which I use at work. Don't even get me started on MakerBot...

PLA really isn't ideal for high impact environments like posts and such for pinball machines. It's probably fine for various toys and decor out of the line of fire, but for parts that take a beating, I recommend printing with ABS or even better, nylon.

My go-to print material is PETG, which prints just about as easily as PLA, but is far stronger (same plastic as soft drink bottles). However, in printed form, it's relatively brittle, so a more flexible material like ABS or nylon should hold up in a pinball environment a lot better.

If anyone needs something printed or reverse-engineered, I'd be happy to either make you a CAD file, print a part, or both. I use Fusion 360 at home, so I could either sent you the raw Fusion file to mess with later, or just the STL to send to your printer.

I wouldn't call myself a hoopy frood, but I can take a swing at it. What is the hole spacing between the posts? I used 0.5" for now, but can change it.
I couldn't get the faceted post to open in Fusion 360, but I did get the star post to work, and made this.

I uploaded the draft file here: https://www.thingiverse.com/thing:3486130

The STL file is there, as well as a STEP file for editing in other programs.
Facetted post (resized).jpg

I do. They're purely decorative, and take a ton of post-processing work (like tumbling or bead blasting) to actually look good.

It's just PLA with metal dust in it. It's hard on your nozzle (I ruined two steel nozzles trying to get CopperFill to work on my printer), the print quality isn't great (lots of stringing for me, which never happens on normal PLA), and it's no stronger (actually probably weaker) than pure PLA.

For a metallic look, you're better off spray painting your part, IMO.

If anyone wants a roll of CopperFill for free, you're welcome to PM me for it, just pay shipping. It's this stuff: https://www.matterhackers.com/store/3d-printer-filament/colorfabb-copperfill-metal-filament-1.75mm-075-kg

I only used for a couple of Benchys, before swearing I'll never touch the metal fill materials again.

Honestly, even the hardened steel nozzles jammed with it, so for just playing around, you're better off running a cheap brass nozzle until it jams, then toss it.
Ruby nozzles aren't worth it unless you solely print in highly-abrasive materials, and have a robust cleaning method for keeping them clear.

Steel wool was the most effective way of post-processing the metal materials I found. I did try tumbling them in brass polishing media, and it didn't do much.

RPis need 2.5 amp power supplies to work consistently. My guess is your stepdown transformer can't put out enough current.

Have you considered PETG? You'll get the majority of the mechanical benefits of nylon, but is much easier to print with, and isn't as hydrophilic as nylon (won't require constant drying).

I have printed PETG parts in use outside as nozzles for my water feature, and they've withstood sun, heat, cold, constant water pressure, etc. I also use it for brackets that see constant mechanical impacts, and it's never let me down. PETG also tends to be quite a bit cheaper than nylon in most cases.