Extruder Z Issues
So I recently built my Mk2s, and have tried printing a few things. After being stupid and ruining a PEI sheet, I later replaced it. Now when I try to print an object, the initial purge line the printer creates is stuck to the PEI sheet, but the actual print doesn't stick to the sheet at all and balls up on the extruder. It seems as if the live z is too high, but if I lower it it starts dragging through the PEI. When running the live Z calibration, at roughly -.4mm the line starts sticking to the sheet during the Z 2.0 file but doesn't stick when printing an object, at -.45 the line starts separating on the sheet (the corners disconnect when turning), and at -.5mm the line makes good contact with the sheet but leaves a light grove in the PEI, but can print the object. I didn't know if I am missing something on the live Z adjustment, or if small groves in the PEI are fine. Any help or tips would be appreciated, thanks.
-Jesse
Re: Extruder Z Issues
You are not limited to 50 micron resolution, so you can try .475.
I also just built my first MK2S kit recently and struggled, as well. I just don't think the built-in first layer calibration process is good for a beginner. If you find a thread I created called "Newbie print failure", dated Feb 03, 2018, I summarize everything I went through. I'm printing fine now. PLA sticks perfectly without anything else on it. I'm using PETG now and I have to use the glue stick to reduce(!) the bed adhesion because it is just too strong.
One thing, in particular, when everyone here says use isopropyl alcohol, they mean it. Denatured alcohol is still not good enough. I was able to get 91% isopropyl at my pharmacy and it is much more effective than denatured alcohol. You literally should not see any streaking on the bed after cleaning it.