Print detaching issues
I've switched from a CR10S to an i3 mk3s and am starting to regret it.
I just can't get my prints to stay stuck.
I've tried brims, rafts, acetone, IPA, etc.
Z adjust down to what looks like a good squish layer.
Never had so much trouble.
Tried a 75x75 live a print at 0.2mm at it looks good one one side but not great on the left.
Re: Print detaching issues
A photo of the bed with the parts loose could help, but, in nearly all cases with the PEI sheets, contamination is why parts lift loose. And fingerprints always precede the issue.
Second cause is poor first layer calibration. and your Layer 1 test is not good. It needs more "mush" ... but it looks fair enough I'd not expect it to pop off unless the bed is dirty. There should not be gaps in the brim, not between extrusion 'threads'. The layer should be welded together as a solid, not stranded.
So try this wash method, and don't skip any steps. Then try another print, and keeps hands and fingers clear of the PEI sheet at all times.
Hot Water wash: often and as needed
Handle the bed only by the edges.
Wash the bed in hot water, use a fresh paper towel as a wash cloth, with a few drops of plain dish soap (Dawn, unscented, no anti-bacterial, etc.). Rinse well in hot water - if you have very soft water, rinse a bit longer.
Dry the bed with a fresh paper towel.
Handle the bed only by the edges.
Place bed on printer.
Alcohol rinse: every few prints
Once in a while, an alcohol rinse is helpful to remove PLA residue. It does not remove finger oils.
Pour a 5 cm puddle of 91%+ alcohol in the middle of the bed, use a fresh paper towel to scrub the bed. Wipe up all the alcohol.
Streak test: when contamination is suspected and after a wash
With a fresh piece of paper towel, and very clean fingers, dampen the towel with 91%+ alcohol, and wipe the bed side to side moving back to front, like you're painting it with alcohol. The alcohol should be thin enough on the towel it quickly evaporates. If you see any streaks, the bed is dirty and needs a wash.
Acetone wash: infrequent
Pour a 2 cm puddle of acetone on the bed, scrub it around with a fresh paper towel. It will evaporate fast as you clean. This step removes PEI oxides that form over time and with heat, and improves PLA adhesion to a like new state.
Re: Print detaching issues
Hot Water wash is all I ever do. once every 6 prints or so.
I have a Prusa,therefore I research.