My print fan has a mind of its own, and it's killing my high-temp prints
Hello All,
I've been having an issue printing with NylonX. (And now ePA-CF SainSmart NylonCF, also)
It's printing fine at 260; beautifully, even. The printer holds steady at 260 -/+0.5C.
My issue is that after about 5-10 minutes printing, the nozzle fan kicks on for a moment and drops the nozzle temp ~1-2C. It recovers OK the first couple times, then the third or fourth time this happens, the nozzle fan kicks on 100% and stays on. I then get a thermal runaway shutdown as the heater and the nozzle fan argue about how hot the nozzle should be.
I'm running through Octoprint; currently 1.5.2, but this problem has persisted since 1.4 at least. Octoprint has allowed me to graph this event; there are no event precursors, just the print fan turning on and starting the cascade.
Problem happened when printing from SD card also, without Octoprint.
I've tried disabling the print fan in Prusa Slicer filament settings; both with "enable auto cooling" unticked, and with it ticked and fan speed set to 0% for min and max.
I have managed to get a successful print by removing the print fan altogether (repositioning to it's pointing away from nozzle shroud). No thermal runaway, hotend temp rock solid at 260, NylonX printing beautifully.
My question is this: why is printer not obeying the disable of the print fan? When I have "enable auto cooling" set in filament settings, it specifies that "fan will be turned off", but that's not what's happening. I'm happy that I can now successfully print NylonX, but would like to be able to do it without removing the print fan.
I hadn't seen this problem with any other filament, and it's the only one I've printed at 260 before the SainSmart NylonCF (which also exhibits this behavior, now). The only other filaments I use are PLA and PET-G, which don't exceed 230. Really not sure if it's happening and I don't notice because the prints aren't failing, or if it's just not happening at all.
Thanks in advance,
Erik
RE: My print fan has a mind of its own, and it's killing my high-temp prints
Open the gcode file for one of the problem prints in a text editor on your computer and search for the "M106" gcode command. That is the gcode that controls the print fan speed. If there are M106 commands other than "M106 S0" when you have the fan disabled and there is no bridging that would cause the fan to run, then it is a slicer issue. If there are no M106 commands other than "M106 S0" then you'll know it is a printer firmware or electrical issue.
RE: My print fan has a mind of its own, and it's killing my high-temp prints
Open the gcode file for one of the problem prints in a text editor on your computer and search for the "M106" gcode command. That is the gcode that controls the print fan speed. If there are M106 commands other than "M106 S0" when you have the fan disabled and there is no bridging that would cause the fan to run, then it is a slicer issue. If there are no M106 commands other than "M106 S0" then you'll know it is a printer firmware or electrical issue.
Thank you for this.
Yes, indeed, I have several instances of M106 S255, and then M107 20-50 lines after.
So then why isn't Prusa Slicer obeying the "fan off" directive? I've had it happen over several iterations of slicing one part, and now another separate part, as well.
Is there a super secret tickbox I'm not finding?
Erik
RE: My print fan has a mind of its own, and it's killing my high-temp prints
Save your project file and then take the saved .3mf produced and zip it into an archive. Then attach the archive here (must be zipped or the forum doesnt accept it).
With the project we can see all your settings and slice it as you would. Its the best way to debug these sorts of issues as there are so many interacting settings or things it could be.
RE: My print fan has a mind of its own, and it's killing my high-temp prints
You might have a configuration line in one of the config files which overrides your settings. (Which might happen e.g. when updating PrusaSlicer releases because sometimes settings get moved between location). You an look at the bottom of the GCode file, there are all the settings used for slicing, and check whether there is something odd.
RE: My print fan has a mind of its own, and it's killing my high-temp prints
I'm guessing your bridges fan speed setting is set to 100%, look for this under the filament settings tab. Even if the "keep fan always on" and "enable auto cooling" settings are unchecked, the bridging fan speed will override these. Note that the slicer considers the first solid layer above the interior infill pattern as bridging and will run the fan at the bridging fan speed while printing these areas.
RE: My print fan has a mind of its own, and it's killing my high-temp prints
I'm guessing your bridges fan speed setting is set to 100%, look for this under the filament settings tab. Even if the "keep fan always on" and "enable auto cooling" settings are unchecked, the bridging fan speed will override these. Note that the slicer considers the first solid layer above the interior infill pattern as bridging and will run the fan at the bridging fan speed while printing these areas.
Yes, that was indeed the case. I was just composing a response regarding that, and that turning that to 0% removed the M106 commands from the gcode, then I saw your response. I'll try gradually adding fan speed here to see if there's a happy zone between the bridges being horrendous at 0% and the thermal runaways at 100%.
This may make for a helpful addition to "tips when printing high-temp materials" posts. It's been plaguing me for months, and my response has been to just not print with nylon because the troubleshooting was not worth it. Another post I had about it only led to doing calibrations to try to resolve.
Thank you for your help; I think this issue can be considered SOLVED.
Erik
RE: My print fan has a mind of its own, and it's killing my high-temp prints
The "nozzle sock" from E3D ( https://e3d-online.com/products/v6-socks-pro-pack-of-3) might help a bit against this problem, as it also shields the nozzle from the fan air (and it helps against filament sticking to the heater block).
RE: My print fan has a mind of its own, and it's killing my high-temp prints
@hli
Oooh, I hadn't thought of that... I have a pack of them, but only tried once.
I'll take a look at them again.
Thanks,
Erik