Thermal Runaway on First Print after 8 or 9 layers
Hi,
I just upgraded my Mk4 to the MK4S and am trying the first print. It seems to reach temperature on the hotend OK but as soon as it starts printing the actual temperature drops off from the command temperature. This can be seen in the Octoprint screenshot attached. After a few layers (Which are really nicely printed!) the print stops with a Thermal Runaway error on the printer. This happens at the same point on 2 successive prints. From the screenshot the thermistor is working but it appears the hotend is not keeping up.....
Note I have updated to Slicer 2.8.1 and I have loaded the MK4S configuration using the HF0.4 nozzle configuration and resliced my STL.
Any help appreciated!
Stephen
RE: Thermal Runaway on First Print after 8 or 9 layers
I saw a similar issue on another thread. Putting a sock on the heater block fixed their issue. Do you have a sock installed?
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RE: Thermal Runaway on First Print after 8 or 9 layers
Hi - no I do not have the sock installed. The sock stopped the hotend from calibrating (as for many other users) so I had to take it off. So now I would be afraid to put it back on if it changes the heating dynamics.
The standard fan speed for PETG filament seems to be 40%. When this kicks in it cools the hotend too much and the temperature drops significantly (I'm sure the sock would prevent this). Dialling the fan speed back to 25% max sorted out the runaway.
The 4S upgrade prints much better than the 4 did and most of the stringing is gone. I do however, still have to dial back the print temperature a lot or PETG gets very burnt and brittle.
Another small consequence is that the high head speeds and accelerations jerk the filament feed system sometimes causing the spool to rotate more than necessary, leading to loose filament and sometimes knitting into the head 🙁
RE: Thermal Runaway on First Print after 8 or 9 layers
Hi - no I do not have the sock installed. The sock stopped the hotend from calibrating (as for many other users) so I had to take it off. So now I would be afraid to put it back on if it changes the heating dynamics.
The standard fan speed for PETG filament seems to be 40%. When this kicks in it cools the hotend too much and the temperature drops significantly (I'm sure the sock would prevent this). Dialling the fan speed back to 25% max sorted out the runaway.
The 4S upgrade prints much better than the 4 did and most of the stringing is gone. I do however, still have to dial back the print temperature a lot or PETG gets very burnt and brittle.
Another small consequence is that the high head speeds and accelerations jerk the filament feed system sometimes causing the spool to rotate more than necessary, leading to loose filament and sometimes knitting into the head 🙁
I remember about a year ago after building my MK4 kit I also had an issue on the first calibration attempt. I don't recall if it prompted me or if I went into the hardware settings to turn on the sock setting. After that the calibration ran without issue.
I haven't seen the issue with the jerking on the spool as the slack runs out. Probably because I have the official enclosure (built at the same time as my MK4). The enclosure has a reverse bowden setup. Are you using the filament guide? I would think it should help avoid over despooling while printing. The guide that I released on Printables helped me avoid filament falling off of the spool on my MK3S+, but that didn't have as many fast movements that the MK4S does...
See my (limited) designs on:
Printables - https://www.printables.com/@Sembazuru
Thingiverse - https://www.thingiverse.com/Sembazuru/designs