Rackfinity 4x HDD (3.5 inch) + PSU holder.

A Rackfinity holder for 4x 3.5 inch HDDs and a PSU for them, as well as a Lenovo 65W PSU for something like this. 

In order to ease printing, I have prepared 3MF files in each folder, combining all the models into a single file. Each print has painted-on supports, sacrificial bridge layers for holes, and optimal print settings applied. So unless you know you need to do something else, you can just print this. (If you are not fitting the Lenovo PSU you can skip printing the PSU-compartment-plug).

The bulk folder contains some parts that I oriented vertically in the 3MF file. If your printer is large enough to print them flat, please do so and remove the sacrificial bridge layers from the models. If you want to print them vertically, please make sure you have good bed adhesion.

The front and back hexagonal grid pieces are designed to be printed in two halves and then combined. Thus, pay attention to which way they are printed. If you have a textured sheet, make sure to orient them in a way where the outside will have the desired texture for you. In this case, you may need to paint on supports onto the joining channel. This is done only on the outer ledge, please don't put supports inside the small canal, or you will not be able to clean it out and it won't work. Alternatively, if you have a big enough printer, simply combine the two using the raw models in the STEP file and print as one piece. Two joined grids are shown in the attached images as an example.

Parts needed for assembly:

• 1-4x 3.5 inch HDDs (each HDD needs 1 top and 1 bottom rail).
• 1-4x SATA data cables (to connect your HDD to your target).
• Silicone anti-vibration sheets for each of the HDD rails (can be cut from a silicone baking sheet of ~1-2mm thickness).
• Flex ATX PSU (I recommend the Seasonic SSP-250SUB, since it has a silent mode at less than 30% load, meaning it will likely never turn its fan on if you only have HDDs connected).
• 1x Custom wiring harness for the PSU (optional, but improves airflow and reduces clutter in the tight space. I attached a wiring diagram for the connector on the SSP-250SUB, but please double-check yourself in order to avoid damage to your hardware. There are plenty of online tutorials on how to make custom PSU wires).
• 2x NF-A9x14 PWM, attached with their rubber nipple mounts (highly recommended to reduce drive temperatures, if you go for different fans make sure they are as thin as the Noctua model).
• 1x PWM fan speed controller and Y fan cable splitter (optional, but highly recommended in order to make the fans silent, the Y splitter comes bundled with the Noctua fans).
• 2x M4x20mm screws per HDD (screwed in on top and bottom of the HDD into the rail to hold it in place).
• 2x M4 nuts per HDD (used to screw in the above-mentioned screws, either press-fit or heat-inserted into the top and bottom bulk parts).
• 4x #6-32 UNC screws per HDD (to mount the rails to the HDD).
• 12x M4x20mm screws (to screw in the front and back panels).
• 12x M4 nuts (for the above screws, heat- or friction-fit into the bulk parts).
• 8x M4x20-25mm screws (to screw the back and front bulk pieces together).
• 8x M4 nuts (for the above screws, heat- or friction-fit into the bulk parts).
• 12x M5x10mm screws (to screw into the rack).
• 12x M5 nuts (to be inserted into the rack where this thing will sit).
• 2x M3x8-10mm screws (to screw in the Flex ATX PSU).
   

All screws are of the countersunk variety to sit flush with the prints.

This model is licensed under CC BY 4.0 meaning it doesn't restrict commercial use with attribution, but I would appreciate if you first talked to me before selling it.