Joining the fairly limited club of stackable PC case designs is MASS, a 3D printable ITX NAS case design from Haydn Bao available for download through Printables.com. We picked up this story due to a recent Tweet by Printables, but technically MASS has been available as a design since January.
Technically, the MASS (Modular Attached Storage Stack) NAS comes in two different models: the MASS Free and the MASS Premium. Either needs to be printed and assembled by the end user, but Premium is needed for users who still want a PCIe slot or Flex PSU bracket. Premium also adds an extra fan slot and supports a few more drives, but is slightly wider than the original MASS Free design. You can print these parts on any of the best 3D printers. You will need around 1-2KG of PETG filament. PLA would not be up to the job, the heat and stresses generated by the components could easily warp the plastic.
If you can stack multiple PCs including drive bays, the MASS becomes quite compelling indeed. There could be some thermal issues though, since the design uses bottom intake, top exhaust— thus higher temps for higher NAS devices in a theoretical stack. But even with just the main stackable design with the 4-Bay 3.5-Inch Drive Bay Caddy (5 on the Premium version), it's still pretty interesting, and one of the most hyper-compact NAS options available on the market.
It's important to stress that "stackable" in this context refers to the main unit housing the motherboard, since it stacks on top of a separate drive caddy. It's unclear whether you can actually stack duplicate NAS PCs with this case, like seen in data center "racks" and occasional mainstream options like the Thermaltake Core V21 or if "stackable" just refers to the drive caddy.
For more detailed information on the MASS stackable NAS design, consider the original Printables model page, which includes a detailed spec sheet and answers to frequently asked questions. There's are also detailed printing and building instruction PDFs available on the same page, which should help anyone who wants to put this design to the test.
As-is, there are dozens of glowing reviews and photographs of the design at work for Printables users available in the "Makes and Comments" section of that page. Since it's a 3D print, some users have opted for visually-striking colors, like white or blue, in their prints. With the modular design in mind, you could make a really interesting-looking version of this NAS with 2+ different colors, should you have the 3D printer and materials necessary to achieve that.
