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So, If I calibrate the towers and radius so that each of the 4 locations is spot on. It still draws an arc. As I tried printing a larger object, anytime it got close to a tower it would dip into the surface and then immediately raise as it travels away. It's very consistent at this, If I try to run a large circle as a test, it is closer to the bed as it gets closer to the tower, and raises in between. Ideas??

I have a stock Rostock Max, just updated the Slic3r, and running latest rep.

We don't need another thread for this issue. Read this post first... http://forum.seemecnc.com/viewtopic.php ... =20#p23853

Mucho Thanks!! I had actually spent some time trying to think of the right search words to get to the answers. I wasn't having much luck narrowing it.

Also make sure your U-joints aren't 'sticky'. If some aren't turning smoothly, it will cause the nozzle to dramatically rise and lower on direction changes even though it is supposed to move on a flat Z plane.