Partially missed / dragged layers I'm trying to diagnose a print issue that looks like a missed layer (sorry, first-time printer here)


and


Specs:


Printer: QIDI Tech X-Plus (direct drive).
Material: PLA.
Extruder temp: 200&nbsp;&deg;C.
Bed temp: 60&nbsp;&deg;C (70&nbsp;&deg;C first layer).
Print speed: 60&nbsp;mm/s (actually 48&nbsp;mm/s on non-infill because of min_layer_time).
Retraction distance: 2&nbsp;mm.


Started from a new printer: I was getting imperfect prints (lesser version of this, functional part) and contacted QIDI support. They eventually replied that my bed was too low but I had since lowered the bed on a misdiagnosis. They supplied a slightly modified G-code but that also failed in a similar way.

Since then, I've been raising the bed bit by bit to try to fix this issue. I don't care about the little whiskers much, but the solid "connecting lines" are a problem.

Questions:


Is this actually a bed-leveling/height issue?
What is this defect called (whatever the cause)? I've been googling but can't find something that looks like this.
Is there a better way of fixing bed height issues than just printing->tweaking bed height->printing?


I'd appreciate any help diagnosing this issue - even if it's just the name of this problem. I have no experience disassembling/looking at hardware but I could always give it a shot.

Update

As per comments I took a look at coasting and ran some tests. I first re-leveled the bed manually (I'll call that height=0). I don't want to add tons of pictures so I'll show the baseline, and "bad" refers to similar failure as above.

+--------+--------------+------------+-----------------------+-----------------+--------------+-------------+
|        | Combing      | Coasting   | Retraction distance   | Extruder temp   | Bed height   | Results     |
|--------+--------------+------------+-----------------------+-----------------+--------------+-------------|
| Test_1 | infill only. | off.       | 2.0 mm.               | 200 C.          | 0.           | Baseline.   |
| Test_2 | infill only. | off.       | 2.0 mm.               | 200 C.          | +0.05 mm.    | ~ Baseline. |
| Test_3 | off.         | off.       | 2.0 mm.               | 200 C.          | 0.           | Bad.        |
| Test_4 | infill only. | off.       | 1.5 mm.               | 200 C.          | 0.           | Bad.        |
| Test_5 | infill only. | off.       | 2.0 mm.               | 190 C.          | 0.           | TBD         |
+--------+--------------+------------+-----------------------+-----------------+--------------+-------------+


(+/- 0.05 mm height achieved with clicks of "fast leveling")

Test 1 external view:


Test 1 internal view:


Update

I think I've confirmed an under-extrusion problem. Here is a top layer printing I stopped partway through.



This looks exactly like Simplify3D's Guide. So I manually pushed through, removed, and re-inserted the filament - and cleaned the nozzle with a brush.

I then ran a new print and noticed a clicking sound in the extruder (I don't know if it's new or if I simply noticed because I was focused on under-extrusion problems) - the print failed in the same "dragging" way as above, but the top layers were slightly better.

I'm now going through the list of possible causes of clicking extruder + under-extrusion.
I managed to confirm the dragged layers were mostly due to under-extrusion.

I had a faulty extruder (clicking sound) and once I swapped it out it was greatly improved.

It's worth noting I also had a slight z-wobble issue so that could have played a role.

Hopefully this can help somebody out as I hadn't seen this kind of symptom in any of the print quality guides.