First layer consistently over-extruded, but good print overall
Hello! I just recently took my MK3S+ and upgraded it to a MK4. Overall things went well, but I had a question about the "Perfect First Layer" of which the MK4 is capable.
When I print a file like this for testing, https://www.printables.com/model/473119-prusa-mk4-single-layer-test-02mm , I get full coverage and adhesion which is great, but it feels like there's a hair too much squish/not enough z-offset as it appears pretty consistently over-extruded across the surface; there are ridges across the entire surface making the whole printed sheet feel "rough". My assumption is that a "perfect first layer" will be smooth across the print surface akin to results I got prior to the upgrade with a properly tuned live-z.
I've printed a 20x20x20 cube and though the first layer is fairly rough like the single layer test, the rest of the print is perfect and the cube is dimensionally accurate when measuring with a set of calipers.
I guess my question is, is my definition of a "Perfect First Layer™" off? Is the loadcell setup adjusting for the bed and ensuring full adhesion by preferring more squish over aiming for "smoothness" or did I mess something up when doing the upgrade and I should be seeing a "smooth" first layer?
RE: First layer consistently over-extruded, but good print overall
you could try setting the Z offset to a positive value in the prusa slicer, Printer Settings>General, tab, to say 0.060 mm
regards Joan
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
RE:
unlike the mk3 series, the live Z adjustment in the Mk4 menu does not seem to persist between prints
regards Joan
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
RE: First layer consistently over-extruded, but good print overall
It is so. Changing Live Z in the printer affects only the print in progress. When you print another object, everything returns to its original values. This is pointed out somewhere in the documentation or maybe even here on the forum, but I don't want to look for it. I haven't tried setting the Z height offset value directly in Prusaslicer (Printer settings -> Offset Z).
RE: First layer consistently over-extruded, but good print overall
In my experience, squishing the 1st layer to some extend makes for better adhesion and nicer bottom surface. What is your elephant foot compensation in the slicer settings. I would say if you haven't set it already to 0.2 mm I would test maybe 0.1-0.2 mm compensation to see if that is sufficient for eliminating the elephant foot.
Mk3s MMU2s, Voron 0.1, Voron 2.4
RE: First layer consistently over-extruded, but good print overall
In my experience, squishing the 1st layer to some extend makes for better adhesion and nicer bottom surface. What is your elephant foot compensation in the slicer settings. I would say if you haven't set it already to 0.2 mm I would test maybe 0.1-0.2 mm compensation to see if that is sufficient for eliminating the elephant foot.
After printing a few more items, I'm inclined to agree. Since my finished prints end up being dimensionally accurate I think I should just be satisfied.
I did fiddle some with the hidden live-z setting and found that 0.015 gave me a "smoother" first layer, but then I had some pieces lift toward the end. That could certainly also be attributed to my ancient PEI smooth sheet 😀 but I'll give the elephant footing a whirl too.
The other change I made yesterday was swapping out my hotend thermistor for an XL version as it seemed to be faulty like others have been experiencing and that also seemed to make a slight difference to my first layer and print quality in general.
Thank you everyone for the suggestions!
RE: First layer consistently over-extruded, but good print overall
One more update:
When I ordered a replacement thermistor I threw in a new heatsink/loadcell to have on hand just in case. Today I decided to swap it in while I was fiddling with other things and then I reprinted the keychain file; that seems to have fixed things! First layer was exactly what I expected it to be when I originally did the upgrade. I haven't run the full sheet file yet but I suspect it should also give me a similar result.
One thing to note. The original heatsink that came with the upgrade kit was labeled: "Da 2137" on the bottom, the new one was "Da 2138". Not sure if that denotes any sort of versioning, but that was the only different I saw between the two parts.
Thanks again!