MK3 extruder calibration weirdness
So the screw in my extruder pulley came lose for the third time, and I decided to apply some blue loctite to prevent this from happening again (but this shouldn't happen in the first place I would think?)
When re-tensioning the extruder pulleys I decided to see how good my extrusion actually was and measured/extruded 100mm of filament. I noticed it was way off, only +- 94mm was actually extruded, so I tried fixing the tension, but this made no difference at all. So I loosened the tensioning screws again and adjusted until it just grabbed the filament reliably, after which I looked into calibrating the extrusion since it still gave me consistently about 94mm.
I looked up the default extruder steps/mm value and this appeared to be 280, so I calculated the new `G92 E*` value, which was 280*(100/94) = 297,87 - rounded up 298. After applying this with `G92 E298` and verifying the setting was correct with `M503`, I did a few new manual test-extrusions, which gave me a spot-on reproducible 100mm each time when manually extruding 100mm, also when doing it in steps of 2 steps of 50mm and 10 of 10mm.
However, that seems to be a quite large difference for something that should have rather tight margins of error? Also, with the new setting, I get filament jams from time to time, so what's going on here? Should extruding 100mm actually extrude less? I don't really get it.
Note that this was all done using the grey filament that came with the printer.