Many thanks for the original design, this is very cool and useful.

I have redesigned just the top and bottom corner bracket in order to fit a 12mm by 12mm square steel tube without the use of glue or anything. (tight fit) In addition to that i have added a T-piece to add support struts in the middle of the top part of the table (1 OR 2 as preferred)

If you want to build one in the same way i did, you need to print 4X the bottom corner bracket and 4X the top corner bracket + 2 OR 4 t- pieces (the Photo has not included the modified bottom corner brackets yet)

In addition to that you will have to purchase 12x12mm steel tubing (4x 240mm lenght + 4x 290mm lengh + 1 OR 2 pieces for the intersection.) Lenght to be adjusted as required.

Also required:

4x 608ZZ Bearings (AMAZON)
3x M8 Threaded rod (10CM)(LM)
1x M8 Threaded rod (12CM) (LM)
4X GT2 Pully + GT2 Belt (AMAZON)
Belt tensioner as required (AMAZON)

for more infos please visit original design:

https://www.thingiverse.com/thing:2299337