This Instructable will show you how to construct a Eurorack case of various sizes, as small as 26HP or as large as you want. Each block varies between 0HP and 26HP wide and you can connect as many of them together as you want.

This is a very simple project that requires few components and just nuts and bolts for assembly.

Supplies

Components

M3 square nuts : These square nuts will be used to slide into the rails. Your Eurorack modules will attach to these nuts within the rails. A rough guide would be about 12 nuts for each 26HP case block you intend to use. 4 to attach the case block to the next case block, and roughly 8 to slide into the rails. They must be SQUARE nuts.
M3 bolts : You'll need 8mm bolts to construct a 3U case, but 16mm bolts if you want to bolt two or more 3U cases together.
3D Printer Filament : To print the Eurorack case blocks
STL Files : To print the Eurorack case blocks. https://cults3d.com/en/3d-model/gadget/expandable...

Tools:

3D Printer : To print the Eurorack case blocks, the bed needs to be bigger than 145x78mm. Various heights are supported, the tallest is 153mm
Screwdriver / Hex Key : The appropriate tool to tighten the M3 bolts you purchased.

Step 1: Print the Eurorack Case Blocks

You'll need to purchase the STL files from here https://cults3d.com/en/3d-model/gadget/expandable-...

The STL file names are...

case3u_B_v2_26hp_left.stl
case3u_N_v2_26hp_left.stl
case3u_B_v2_26hp_right.stl
case3u_N_v2_26hp_right.stl
case3u_N_v2_0hp_right.stl
case3u_N_v2_6hp_middle.stl
case3u_N_v2_8hp_middle.stl
case3u_N_v2_10hp_middle.stl
case3u_N_v2_12hp_middle.stl
case3u_N_v2_16hp_middle.stl
case3u_N_v2_20hp_middle.stl
case3u_N_v2_24hp_middle.stl
case3u_B_v2_26hp_middle.stl
case3u_N_v2_26hp_middle.stl

Your case will need one "left" and one "right" and can have as many "middle" 's as you want. Add up the HP numbers in your filenames to get the width of the case. Examples...

26HP Case : case3u_B_v2_26hp_left.stl & case3u_B_v2_0hp_right.stl
52HP Case : case3u_B_v2_26hp_left.stl & case3u_B_v2_26hp_right.stl
78HP Case : case3u_B_v2_26hp_left.stl & case3u_B_v2_26hp_middle.stl & case3u_B_v2_26hp_right.stl
104HP Case : case3u_B_v2_26hp_left.stl & 2 X case3u_B_v2_26hp_middle.stl & case3u_B_v2_26hp_right.stl

I recommend trying to construct the smallest 26HP case first, just in case there are any issues that need to be resolved.

Step 2: Put Everything Together

Starting with the left case block, slot the next case block into it and add four nuts&bolts into the four holes to secure them together.

If you have more blocks to add, then continue this process until adding the last block, and securing with four more nuts&bolts.

Now you can slide the square nuts into the rails by inserting them into the slot on the side of the case. Each case block has 2 slots in the middle, one for each rail. You need as many nuts as there are holes in your modules.

Once all of the nuts are in, you can now start populating your case with your modules!

You should print out blank panels to fill any remaining space not occupied by modules, to prevent patch cables falling into your case and shorting out, causing damage to you and/or your modules.

That's it!

If you have any problems printing or constructing your case, then please add comments below!