This is modified from a mATX board make by lightofhonor to be able to fit a full-size ATX motherboard and PSU. I had an old built PC laying around and wanted something smaller and different that I could print. All of the parts were modified to fit ATX and to also be able to print on a standard printer.

The beams needed to be extended so they could support the whole board so they were split and can be printed alongside the PSU parts and support bar on one build plate.

This is a great way to get rid of your bulky old tower case or repurpose an old motherboard and parts!

What to print:

1x ATX_PSU_right
1x ATX_PSU_left
2x ATX_Support_Bar
2x ATX_Case_Beam_MF
3x ATX_MB_Beam (print diagonally)

9/28 Update (If you intend to use the 2.5" drive mount)
1x ATX_2.5_SSD_Mesh
2x ATX_Mesh_Brace_bar

The tolerances for the parts are all around pretty tight so if your printer is not capable of 0.20mm tolerance, you may want to modify some of the mating surfaces to allow them to piece together. You shouldn't need any glue if they print correctly, although my parts did require some manual persuasion with a rubber mallet to get them flush.

My Print Settings:

0.20 mm layer height
4 perimeters (you could get away with 2 or 3, I just wanted some more rigidity)
1 support for the ATX_PSU_left overhang portion

Additional parts/Assembly:

The only external parts you will need are the motherboard standoffs to mount the MB_Beams to the motherboard. These are screwed directly into the holes of the MB_Beam but be sure not to over-tighten them.

I haven't figured out any mounting for SSD's or HDD's but that will be my next step in the process and then maybe cable management.

UPDATE 9/28/24:

I added a mount option for 2.5" drives, this has been specifically tested with a 2.5" SSD. Both the Mesh and the Mesh brace slot onto the support bar opposite of the power supply before placing the horizontal dovetail beams.

Pt.2
Widened the Case Beam square hole to fit better on support beams.