Print shifts (single shifts not continuous)  

Print shifts (single shifts not continuous)

Hey,

Loving the Prusa i3 MK2S ! My first prints were flawless. However I let the printer sit on the floor for a month or two in my apartment (which stays around the same temp usually), took it out, and it needed a recalibration and the print I made had one or more SHIFTS in it.

These weren't continual shifts, but shifts here and there occasionally. My current theory is that this is due to me attempting to print to the very edge of the print bed. I note that when my printer starts up and sometimes when printing at the very edge the X-axis would "stutter" as it's hitting the limit. It would do this when trying to print along the edge as well. My theory: I believe this may have caused the printer to internally think the X-limit was more or less than the actual limit of the bed. Any temporary "offset" in it's memory would likely cause a shift in that entire layer. I did see a shift across all parts roughly at the same layer (I forget exactly but I'm pretty sure I saw this). Sometimes the shift varied in amount per part. I dunno about that.
Another theory I have is that its due to some sort of skew that is inconsistent across the bed. So that some parts have a different amount of shift depending on their position on the bed. Not sure.

It is currently printing another part which is much smaller and centered on the bed and it is having no problems. This is why I believe it was due to me printing at the very limits.

At the very least, this shows that there is some sort of bug when determining the maximum X value that the printer can go. I remember there's no X-stop for this thing right? Perhaps we need one?

FYI this is a brand new printer I assembled myself. Only other flaw I can think of in it is that I left the Y carriage squaring bolts a little looser than I should have probably but I wanted to be able to press down on the 4 corners to flatten the bed (I do this frequently). Also it is more difficult to tighten the corners without unintentionally putting twist on it. You'd need to clamp the bed in between two perfectly flat surfaces before tightening down in order to ensure there was no twist put on it when you tightened it.

Anyways that's all for now. I've been printing parts I made from CAD and I'm surprised how easy CAD is compared to regular 3D modeling. Its like woodworking or machining! I'm using OnShape to do it which I'm very impressed with despite it being web-based & Android software. I do find that the tolerances of hole-widths are somewhat generous, up to 0.75 mm sometimes. I wonder if this is because my filament is too squished? I remember live-adusting-z so that it was a pretty squashed line and alot less a bead.

Toodles and happy printing!

Shorin