3.5'' HDD cage for AliExpress SAS backplane

Exactly what the description says, this is a 3D printed cage for an inexpensive 4x3.5'' SAS backplane found on AliExpress.

The backplane in question:

https://aliexpress.com/item/1005008761856159.html

Current version is 5.1. The holes for the backplane and fans are meant to take M3 inserts, while the vertical holes are intended for threaded rods to hold multiple stacked modules together. The stacked modules seem to be pretty sturdy, but I would not personally stack more than 3-4 levels. I also advise to fill the slots from bottom to top, so the hard drives support most of their own weight. The shelves are surprisingly strong, and with decent airflow should not get hot enough to deform or break, but it is safer if we rely on them mostly for electrical separation. As with the previous versions the prototypes have been printed in PLA+, but now that the design is final I intend to switch to ABS-GF.

Hard drives are held by friction and are pretty secure. Once I design the rest of the case to go with this system I will add some foam to the side cover of the case so it presses against the front of the hard drives for extra safety. But otherwise HDD replacement is meant to be completely tool-less, that is a hard requirement for me.

The light pipes for the status LEDs are made with clear PLA filament threaded through the holes, cut flush and held in place with a drop of CA glue. I use a very long 2mm drill bit first to make sure the holes are clear, but with good print settings it should not be necessary.

With two columns side by side, one 1700RPM fan on each side and a shared central fan (see pictures), the thermals seem to be ok. Right now I have an ambient temperature of 32ºC (no AC at home, and summer has not even started properly!) and the drives barely go past 45, which is as good as I can expect short of a miracle. With a more reasonable room temperature you can expect them to stay below 40ºC.

I have attached two versions, one with breakable supports for the thin vanes on the right side and one without. The H2S at work had no trouble printing everything without supports, but my personal heavily modded Ender 2 is a lot slower and needed some help to keep them from flapping around in the breeze. Like I said, the prototypes are made in PLA+ but I will make a new set in ABS-GF as soon as I can for better thermal stability over time.

I think that's pretty much it. The design is (for me at least) feature complete. I will still design and upload here a few extra support pieces to bolt the modules to a surface and secure multiple stacks together side by side, but I will mostly concentrate on designing the rest of the server case to go with these modules (current plan involves aluminium extrusions, MDF and laser cut acrylic panels). For anything else, I have uploaded STEP files along with the STLs so anyone can tweak the design to their liking.

[For the old V1 and V2 prototypes]

Prototype printed in PLA with a Bambu H2S (front facing down with tree supports), but my Ender 2 v3 can tackle it just as easily. The holes are meant to take M3 brass inserts. Once I polish the design I intend to switch to ABS+GF for better long term stability (although the PLA does not seem to have any problem as long as the fans keep temperatures in check).

This is a work in progress. I still have to figure out a good way to hold them together when stacked and to make some kind of lightpipe for the activity LEDs, but as of now it is more or less usable.

The early V1 prototype in the picture has basically no airflow and despite being so tightly packed the drives have surprisingly good thermals, maintaining 31-33ºC in SMART over a weekend. The only catch is that I have been testing it with the only fan I had available, running at 3000RPM unregulated all the time. It sounds like a jet taking off and I have been regretting my life choices while a more reasonable solution arrives. I expect that V2 with the side air outlets should work just as well with a slower fan. [UPDATE: V1 with the fans set at 1700RPM tops at 38ºC, which is more than acceptable. V2 tests coming soon.]