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I am trying to configure my Ender 3 v2, but I am having (again) trouble with layer adhesion: With the CHEP leveling test I am having these problematic "blobs" at each lower left of the squares (where the nozzle "leaves" the current square and "enters" from the previous (outer) square, touching the bed again). I don't know what the reason for that could be. I started with a 205 °C nozzle temperature and a 50 °C bed temperature and tried many versions with higher or lower temperature (both for nozzle and the bed), and I also tried various positive and negative Z-offsets. Sometimes the layer adhesion was slightly better (especially when raising the bed temperature to 60 °C and making the Z offset = -0.2), but the blobs persisted (and each time the nozzle scraped over it, the layer was pulled off again). Any idea what I should try next?

enter image description here

EDIT after your suggestions: While I have not reduced the distance between nozzle and bed further (a sheet of paper between them almost ripped when trying to move it), you got me thinking and I checked the extrusion. And indeed, the extrusion factor was way off. After calibrating the results look now much better: enter image description here

The lines are squished much better into the bed, and also the blobs are much smaller (and less "prominent", i.e. lying flat). But I am still having (slightly smaller) problems at the same points (lower left corners of the squares): While the initial adhesion is fine (the nozzle starts at each square in the lower left corner and then travels "right, up, left, down", i.e. counter-clockwise), it comes loose when the square is completed (due to the nozzle "hitting" the blob in the lower left corner at the end of the square.

What can I do next in order to improve things? A lower Z-offset (trying to eliminate the blobs further) has not really worked.

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  • $\begingroup$ What speed are you printing at? $\endgroup$
    – R.. GitHub STOP HELPING ICE
    Commented Mar 15, 2022 at 14:35
  • $\begingroup$ My Cura slicer is set up with a print speed of 50mm/s, and the gcode file has a line M203 X500 Y500 Z12 E120 ; sets maximum feedrates, mm/sec, so I don't actually know whether it is 50mm/s or 120mm/s $\endgroup$
    – Philipp Wacker
    Commented Mar 15, 2022 at 14:52

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It looks like your nozzle distance to the bed is still too high, so the extruded material does not start sticking to the bed until there's a small blob of it on the nozzle end. This is consistent with how the extrusion lines in the photo seem to be round rather than flattened against the bed. Assuming 0.4 mm nozzle/line width and something like 0.2 or 0.3 layer height they should be a lot wider than they are thick.

It's also possible that you may have retraction speed or distance problems going on at the same time. If your retraction distance is too high, the material will cool while retracted and then will not be able to push through the hotend/nozzle until it re-melts, possibly causing skipping or delayed extrusion when you unretract and restart. But if so, I think this is secondary and you should fix the bed height first - then you can print retraction test towers to tune your retraction.

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  • $\begingroup$ I have updated my printing situation after taking into account your hints. $\endgroup$
    – Philipp Wacker
    Commented Mar 15, 2022 at 14:03
  • $\begingroup$ @PhilippWacker: You should not have to significantly change the extrusion factor if you haven't replaced the extruder with an aftermarket one. If you seemed to need to do that, yours might be broken (cracked arm) or have tension problems. $\endgroup$
    – R.. GitHub STOP HELPING ICE
    Commented Mar 15, 2022 at 14:29
  • $\begingroup$ No, actually that is due to a different extruder that I installed. I measured the correct extrusion factor before (matching the current one), but somehow in the meantime the value was reset $\endgroup$
    – Philipp Wacker
    Commented Mar 15, 2022 at 14:44

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