Bed leveling damage build plate
I finished my Mk4 build this weekend and have 3 successful prints so far. I have been really enjoying using the printer! Build instructions were really great and tolerances are so tight, which made the build easy.
One issue came up today somewhat randomly on my 4th print with the printer. During the bed leveling test, the nozzle just rammed into the bed halfway through (like 21 points into the over 40 points) the process, damaging the plate in one small spot. The action was not as slow as the typical process follows to probe the points. It hit hard enough to make the Z axis crooked. It was fixed with a z axis calibration, and I am printing successfully now again.
Is there something I did wrong? It seemed to happen randomly, with no difference from the previous successful prints and the one immediately following the issue. I am a little frustrated to have damaged a print bed with seemingly no explanation. As of now I can't explain how it happened, so I can't correct whatever the root cause was. Should I be re-calibrating the axis regularly to avoid this? Thats the only thing I can think of.
RE: Bed leveling damage build plate
I just had a similar issue occur to me, but my MK4 had been printing fine for probably close to 50+ prints before this problem occurred. I'm on 5.1.2 firmware. In my case the bed probing seemed to go fine, but when it did the last final probe right before printing in the front left corner pressed really hard into the bed, knocking the z-axis off level and putting a nice dent in my build sheet. I contacted support to see if they could get me a new build sheet, but they state that perhaps the issue was the filament was coming off the spool a bit tight and causing negative pressure on the load sensor. Not sure I buy that though, as that would seem to have made the probe early (too high) and not well beyond the plane of the bed. I know there were issues in the past (from doing searches) where build plates were being dented, but thought it was resolved in later firmware versions. Perhaps that is not the case? Curious if others have run into this problem as well on the latest firmware.
RE: Bed leveling damage build plate
Thanks for the help!
I did not check my active firmware when the issue happened, but I have since updated to the current 5.1.3. I am not sure what my kit shipped with.
I have a dozen or so prints since this issue and haven't seen a repeat occurrence, so I will stop thinking about it. I do think it is possible that the filament was a little tight as you suggested, I had just loaded the 25g sample section from Prusa, which is not on a spool. Perhaps it was caught on the spool holder awkwardly. I don't understand how tight filament would cause this though, intuitively it seems like it would have the opposite effect of registering a false probe too high from the bed. But I don't know what I don't know. As of now I'll assume this was the issue.
I will add that the probing process before a print results in a single probing over most of the bed except the back right corner, which requires an additional probe over a few points. Perhaps the bed or build plate isn't completely level. I will see what the new textured build plate looks like when it arrives. I have tried loosening the rod holders and moving the y carriage through the travel and re-tightening per the assembly instructions again but get the same result. I am not too worried about it since the first layer is flawless 100% of the time so far, so the probing process clearly works.
RE: Bed leveling damage build plate
When introducing the filament, I omit the arm with the dies and lead the filament from the spool directly into the extruder. It can happen with FLEX when the filament is kind of sticky and can catch a bit on the edge. The same applies to filaments with fillers (wood, carbon) when the filament is rough on the surface.
And as for probing, I believe that a few touches at the first calibration point is correct. The nozzle is thus set to the first calibration point during the actual probing of the height of the printing plate, and then it is related to this point when compiling the height map of any unevenness.
RE: Bed leveling damage build plate
I have run into the issue again, now both sides of my PEI plate have been damaged. 🙁
I did notice that the trapezoidal nut on the right side (where I have had issue) seems to be wearing. It has a little bit of play and the left side does not. I swapped it out for a new one and the play was gone for a number of print hours, but now the right side feels a little loose again. I have noticed a spiral mark on the right z-axis stepper threaded rod confirming the wear from the trapezoidal nut. I don't think it is misaligned because the threaded rod is pretty well centered before I installed the new trapezoidal nut. I believe this could be the root cause but I really don't know. Considering that the trapezoidal nut has some slop in the connection, during the probing it could possibly not register a touch as it is not firmly held in place (specifically on the side of interest).
Anyway, no definitive root cause to share with the community, but if you have some slop in the Z-axis you might want to check the trap. nuts. Curiously I haven't had an issue yet with my textured bed and PETG prints.
RE: Bed leveling damage build plate
PEI Sheet is softer than Powder Coat.
Also PEI Sheet, has double sided adhesive tape under it which is also relatively soft
I try to make safe suggestions,You should understand the context and ensure you are happy that they are safe before attempting to apply my suggestions, what you do, is YOUR responsibility. Location Halifax UK