3D-printed 4-in-3 HDD bay

Updated version 2: Fix the drive rail part STL.

This is a 4-in-3 hard drive cage with cooling fan. It fits four 3.5″ drives in to three 5.25″ slots. It can be used inside a standard PC case or on its own with no case.

I often need portable drive cages for moving drives around with built-in cooling so I designed this. It’s a compact rigid structure. I recommend printing it “face down” with infill for the first 7mm then no infill for the rest of it. I usually use a fast “draft” mode (0.3mm) for printing the cage faster since it doesn’t need to look nice.

The drives are held in place with small tool-less rails for easy drive swapping.

The drive rails can be tricky to print depending on your printer. I recommend printing them in “normal” orientation with the pins sticking out to the side. This requires a tiny amount of support material for the pins but will make them very strong. The Z axis accuracy of the printer and first layer is very important for the rails to fit the cage. They are suppose to be exactly 6.2mm wide (or “tall” on the print bed). This is critical for getting a good fit.

I know the fan is a bit of a pain to mount, requiring screws on the inside. I tried designing retainers that could be inserted from the front but they’re too small and thin to be printed on a FDM printer reliably.

Some notable points about this design:

This is a rigid structure that does not flex much and when a fan is mounted it’s even stronger.
The weight is distributed to the sides to prevent flexing.
The drive rails distribute the weight to the sides across a wide cross-section in the strongest direction of the plastic. Less chance of the plastic layers separating over time.
It is tool-less. No screws unless your PC case requires them. Not using screws also helps prevent the plastic from separating over time.
This will fit in PC cases that use shelves for the 5.25″ slots.
Active cooling directly attached via 120mm fan.

Note: This cage only works with drives that have 3 mounting holes on the sides.

This design is on printables as well.