This is a printable version of the frame used with these models:

• https://www.thingiverse.com/thing:2879686
• https://www.thingiverse.com/thing:2577853
• https://www.thingiverse.com/thing:2759317
• https://www.thingiverse.com/thing:3552375

etc.

The current name of the official frame seems to be "Middle Atlantic FK2".

This design was originally based on the technical drawing linked here: https://www.thingiverse.com/thing:2879686#comment-2769823

But those dimensions don't match the modules available on Thingiverse. In particular, the vertical distance between holes in the rails is listed as 80mm, but the modules have them more like 95mm apart.

There is another printable version of the frame here: https://www.thingiverse.com/thing:4062295

I found the joints very brittle, so I designed this. It's built to fit an Ender 3's built plate.

Assembly

There are 2 parts, and you need 2 of each.

They're joined together with M4 screws (I used M4x10 IIRC). You'll need 4 of them.