RE:
After some more tinkering, I think there may be something to the dirty nozzle idea. I haven't dinked with filament tuning on this upgrade build yet, and PLA always works.
Since Prusament PETG seems to ooze less and gives me a better first layer, as opposed to every other PETG I've tried, I'm thinking there may be some retraction settings I could change to improve my case.
As noted above, the printer has a nozzle cleaning routine it does, but the 170C is not hot enough to smash the PETG that is on the nozzle. Cleaning the nozzle before printing only works, it the plastic doesn't ooze and harden before the bed mesh.
RE: Problems with first layer being too high off of the plate
Agreed that 170 is not hot enough to clean the nozzle. I go into control and temperature and turn the nozzle to 230 for PETG and then lightly brush it with a brass brush.
Then I either preheat the printer or just select the file I want and start the print.
RE:
Hm, this was announced with "no more first layer callibration". Unless you have a cleean nozle and using the smooth sheet, any left or oozing filament on the nozzle tip can degrade the MBL before the print. Textured sheet surface can add another bit of degradation. A print which sticks on mk3 as hell can fall on mk4 fall during the print.
RE: Problems with first layer being too high off of the plate
I've changed the startup gcode to bed-level at 40 degrees less than target temperature, which seems to work okay with the exception of PC CF that requires me to pick up any ooze with tweezers.
Formerly known on this forum as @fuchsr -- until all hell broke loose with the forum software...
RE: Problems with first layer being too high off of the plate
on my mk3.9 i have never had any issue with first layer being too far away from the bed, not a single time.
i use the satin sheet with petg and some pla, using 5.1.2 firmware.
i almost only use prusament filament
i read somewhere a recommendation after fw update to redo the first time calibration wizard since this changed between some of the fw releases and could fix some issues.
RE: Problems with first layer being too high off of the plate
With PETG there is always a small drip and sometimes a buildup on the nozzle, especially after a long print. If you just leave that on there then how do you expect to get a proper first layer using a dirty nozzle? It's got to be clean to work properly.
Now like I said there should be a built in brush that cleans the nozzle before each print, but since there's not you have to make sure the nozzle is clean before you start or you chance a bad first layer.
RE: Problems with first layer being too high off of the plate
I've realized that the issue only seems to occur when using a 0.6mm nozzle (at least for me). Previously I was printing using a 0.6mm nozzle and the issue would happen regularly so I would need to babysit the printer and manually tweak the z-setting once the print started. To note, I always ensure the nozzle is clean before the probing occurs by wiping it with a paper towel. Regardless, the first layer was always inconsistent and required manual z adjustment.
I've now switched to the default 0.4mm nozzle, and the first layer has been consistent without problems after 10+ prints already. I've used both the satin and smooth sheets and both work fine in terms of the first layer not being too high.
RE:
I too am having the issue with the first layers being too high. It happens pretty much randomly. But rarely twice in a row. I own 2 Mk4 printers, and both have the occasional bug. I have been in contact with support and they told me to do various checks and also tighten the thumb screws again. But nothing seems to help.
Seeing the Prusa commercial on YouTube boasting the 'always perfect first layer' is a constant slap in the face too. I can't imagine Prusa not being aware of this issue. It seems to be occuring often enough.
I don't think it's got something to do with a dirty nozzle. Since I've literally stopped an affected print and then pressed reprint again without any cleaning whatsoever and it would work just fine. I think it's some issue with the load cell sensor or some slack somewhere on the Z-axis (nozzle or rods).
I've now switched to the default 0.4mm nozzle, and the first layer has been consistent without problems after 10+ prints already. I've used both the satin and smooth sheets and both work fine in terms of the first layer not being too high.
Could it be that one of the steps required to swap the nozzle actually helped solve the actual cause? I assume a lot of us here are using 0.4 nozzles, so i wouldn't expect nozzle diameter to be the cause.
Maybe it's the thumb screws? Maybe they come loose ever so slightly during prints? Perhaps your issues returned on a later point in time with the 0.4 nozzle?