Yes,about the epoxy, the 10mm at each side is ok, given that you weld to the mm the frame.

i also am wondering about that diagonals and at the same time big holes in the middle. I don't know the top you are planning on but generally i wouldn't have a hole in my table bigger than 300mm, otherwise you will need 50-70mm top if made from ply or similar. even alu top would benefit from such maximum distance.


IMHO you are mistaken about the ball screw end mounts. Do yourself a favor and design it similar like i did them from 10mm plate and additional plates that screw to that perpendicular reinforced with ribs plate.
Or you could find your self in a scenario that you have to file shims or even worse, what you will do if the ball screw has to go inside direction?
I believe the way i did it was simpler especially for precise alignment of the ball screws. Meaning that when gantry is mounted and squared, i just screw the nut to the nut plate and moved the gantry one side by hand. Screwed the ball screw mounts, then repeated at the other side. Then tightened. So no fiddling with alignment and so.


About the welding i also have not welded before. Played around a bit , watched some videos on YouTube and was good to go. Just remember- if arc or mig welding the most important thing is to keep the arc at the same distance and watch the pool and spread it, not think about quality, instead think about welding strong with good penetration. just zigzag to ensure penetration.