Strange bed leveling issue
I purchased my Prusa i3 Mk3 assembled in October 2018. I've always had trouble printing things in the corners of the bed. Anything towards the center prints fine, but large objects or multiple objects that extend into the corners end up rough like the picture below or often fail completely. One example:
Raising the live-Z value helps some, but at the cost of adhesion in the center. So it behaves as if the bed is dish shaped without proper compensation.
Today I decided to take a run at fixing this problem. I installed a Raspberry Pi and Octoprint and ran the Prusa Mesh Leveling plugin. The result:
While the amount of variance is notable (1.4mm), it is linear , not the dish-shaped map I expected. It does not explain my printer's behavior . And I would think that the firmware would handle a linear variation well. So I suspect there is some geometry problem with the printer that is not (directly) a bed level problem. I purchased this machine assembles, so I don't know a lot about the geometry of how all the components fit together. Any idea what might be causing these "dish-shaped" failures? Or any suggestions with diagnosing the problem?
RE: Strange bed leveling issue
Could it be bed temperature related ? The corners are usually not as hot due to the way it heats up.
RE: Strange bed leveling issue
I'm not finding warping due to uneven heating to be the problem. I ran this calibration test:
https://www.thingiverse.com/thing:2838514/comments
It uses squares a single layer think, and I ran the test with PLA. The front two corners were roughed up like my picture, but there was no indication of warping of the material away from the bed. Thanks for the suggestion.