Video of project: https://youtu.be/p55gvl1gWus
I wasn't thrilled with the price of the very small SFF cases so I decided to take a stab at designing one myself. I already had a parts list in mind so this isn't the smallest I could make it, but had a few qualifications in mind.
1)Printable on regular 3D printers. I designed this initially to print on a Cetus3D Extended, but also kept it in line with a Creality Ender 3. Printed dimensions 147x179x250mm (6.58L)
2) Have as much as possible 3D printed. Only thing you need is standoffs for the PSU, a power button, and a PCIe Riser if you want a GPU. You could probably mount several 3.5in Drives where the GPU would go, though I didn't try. Depending on your PSU standoffs, you may need a right-angle power cord.
3) Print with zero supports. Hate removing them, so design around them.
4) Needed to hold an ITX GPU (~170mm), 70mm CPU cooler, and SFX PSU. Only officially supports M.2 drives.
5) Minimal Assembly. Prints in two parts which can be attached with case screws, though not needed.
Power Switch: https://ebay.to/2J4hE3L
PCIe Riser: https://amzn.to/2ZSn7Qh
35mm M3 Standoffs: https://ebay.to/2Wjflh6
1ft C13 Right Angle Extension: https://ebay.to/2ZIxJC5
Thumb Case Screws: https://ebay.to/2IRbRPX
C14 Socket (if you want to hard mount power cable): https://ebay.to/2V8PsnN
CPU Cooler- Scythe Big Shuriken 3: https://ebay.to/2IR7Pps
Motherboard- Asus Strix B450-I: https://ebay.to/2FCvhVc
PSU- Corsair SF600: https://ebay.to/31WK0UJ
Extended version adds space for 1 120mm fan (or 140mm fan with 120mm holes). Interior remains the same. I used this fan: https://ebay.to/2E3dUwc
.3mm Layer Height
4 outer layers (Could go less, but since we are screwing things into plastic I went the safe route)
At 60mm/s (.4mm nozzle) inside takes ~17 hours, cover takes ~38.
Will use ~0.8KG of PLA. ~0.5KG for cover, ~0.3KG for interior.
Other than PSU, everything should mount with case screws.