Sorry to resurrect an old thread. My company began to require us to come back to the office now that everyone has been vaccinated. Sucks because it really cuts into my 3d printing time
ANYWAY. @dc42 I did exactly that as one of the last things I tried. I still get 1-2mm of difference between towers. I have a heavily modified Rostock Max and even gone as far as to put belt tensioners on the top to ensure proper tension.
I have found that instead of equally tensioning the towers I can tension them to get equal movement, but that really doesn't seem like the right thing to do. One is very taught while another seems to be quite loose.
I suppose you could argue that mesh leveling would sort that out, and to a point it does but I still get some discrepancy the further out I go between the XZ towers, everywhere else is great.
Seems a lot like the individual arm length is the culprit but I've moved the arms around and the same issue exists in the same place. Side note, I've even tried to rotate the effector, same thing. To me this would then maybe indicate that one tower is off with regards to steps/mm (or whatever has a direct effect on that measurement). Sure enough there is a significant discrepancy between all of them, with more on the Y tower.
So far I haven't 100% tracked this thing down, I can solve by printing a raft and the print comes out great, and dimensionally accurate.
Any other suggestions of what to try? Before you say it, I have confirmed with an engineer square that the towers are square and the build is rigid.