Hi Arm - Your design will work just depends on what you expect it to cut and at what speed? Do you want to make titanium aerospace parts
Not sure why you want to epoxy level on angles. Commercial angles will be twisted and not straight. 15mm rails are quite compliant and will conform to the foundation easily. Start with a straighter thicker section maybe a channel will be better as it will have less twist.... Looks like you intend to weld some things (I recommend you don't) bolt parts together instead so you can adjust. High strength bolts are better then rivets and there are many rivetted structures that have been around forever eg Eiffel Tower and modern aircraft...Its a large machine and your machine base will need to be more substantial. Vibration is always an issue with thin metal eg your angle irons.... Peter
The gantry will be better if its smaller then 100x200 and thicker. 4mm will be a bit springy locally...excellent globally but locally where you have your angle welded to it its not good. Better to have thick walls you can drill and thread to ....