When we started this project with my friend, we have very ambitious ideas and we made a big mistake – began right off built a big CNC machine without any experience in these field.
One of the main problem is twisting of the gantry.
If you look at the picture, you can see white contour which shows the location of the gantry bulk, Z-axis moving along this beam. Violet arrow show the shoulder between bulk and weight(red contour around milling tool) on the Z-axis. Plus, Z-axis itself have a big height (green arrow). All this construction’s “features” giving a twisting gantry while X-axis or Z-axis moves.
Now I try to solve this problem using little changes in assembly of the Z-axis.