Shutdown due to temperature drop on specific layer/height on diferent files

General Discussion
1

printer: vzbot based custom config
board: robin nano v3 w/ klipper
slicer: orca

logs and videos.zip (7.5 MB)
klippy.log was to big so i compressed it, also put together a gcode file of my last print and video of the issue itself

So, for a litttle over a month i’ve been having this issue where the printer, sometimes at random and sometimes at a specific point/geometry/move, but mostly random, shutsdown due to large temperature drops on extruder.
i can’t make sense of what might’ve been causing these since recently i just installed a brand new voron style/v6 high flow 300c hotend (it began a little after i installed the hotend) and doesnt seen to follow a pattern.

-before the large drop itself leading to the shutdowns, the printer prints just fine, everything works fine
-not sure if it’s just a impression, but i feel like the shutdowns usually happen when i’m printing with higher temps (230/260) i don’t remember much of then happening with pla prints
-also sometime mid print i’ve noticed some temp oscillations, not enough to shutdown, but 5/7/9c temp drops, i just cant find a pattern
-i tried cleaning the board, checking for loose wires and connectors, etc
-wasn’t having any issues for some days, untill now

-More recently (the main issue, since these shutdowns and drops were happening but were not very frequent, but now…) i had 4 prints (similar models with very similar geometry) fail in the exact same spot, in the middle of the first contact layer with the support interface, all 4, same height (layer 282 if you want to check the gcode)

all of that said, yesterday i spent over 4 hours changing all wires and connector from the hotend to the board, cleaned everything, put brand new wires in, started a print and…same thing, on the same spot

2

little update, ran some more tests and saw some past timelapses of some failures, from observing the past 7 prints that had this issues, i noticed that everytime the shutdowns happend it was on a ‘‘high flow area’’ mostly bridges (i had the ‘‘thick bridges’’ option on, so flow for bridges were around 30 to 33mm cubed
so now i think the shutdowns might be because the hotend can melt the material fast enough??
or could it be something else? i only compared my past 7 prints, only had saved project and timelapses of those 7, but still all 7 had, apparently the same ‘‘cause’’

image
image798×649 156 KB

image from my last print, it failed exactly at this red bridge area above the support
flow here was around 31mm cubed/s and the rest of the print was around 20 to 10mm cubed

3

btw, my hot end config is one of these:

image
image322×308 39.3 KB

with a 0.4 nozzle

i’m going to try and print the exact same object from my last print, with the same configs, only with thick bridges turned off now

4

just finished a print of the same part i tried that last time, no issues at all, finished without shutdowns

that said, is it normal for such a hot end, even tho 30mm cubed flow is almost pushing the hotend limit, for it to just shutdown? i already ran hundreds of max flow tests on dozens of printers throughout the years, everytime i was pushing the flow limits, the printer with either show extrusion flaws, underextrude, skip steps on the extruder, grind the filament, and so on, but never shutdown due to temp drops, this would be a first for me
so, is this normal?
board issue?
hotend issue?
power supply? (not enough power being delivered)

5

I have heard from my brother who had a similar hotend construction where the heater cartridge is kind of enveloping the nozzle instead of it being a cartridge or something like that, that he experienced dropped hotend temps. He inspected everything like you did, but in the end it was the ceramic housing of the hotend heater that had cracked and caused loss of heating.
I would disassemble that hotend and carefully inspect all of it. You might have to take some parts of it before you can see the heater element or this ceramic housing. Bro told me it wasn’t very clear and only after he looked at it with a loupe he could see it. Very small hairline cracks.

6

i did so, among other tests, i think i’ve found the answer already, the advertised max flow is a bit exagerated, the thick bridge option was causing various small section of my prints have around 28/32mm cubed flow (advertised is max 33mm cubed) and even with some highflow materials, i was having rather larger temp drops.
but, i just turned the thick bridges option off and so far, have printed over 50 hours, with 0 issues