how to save hotend PTFE tube in power outage
After 14 days, I've finally finished my 11 day print during which I've got several hours of power outage.
Once I was sure power was back on, I've recalculated the last position of the print head, unstuck it from the print, homed manually, as auto homing would cause a collision, edited the gcode and got back to printing. It wasn't amazing, since I've lost the bed leveling data (any way to get that out of the printer and then reinsert on print restart?), but the print would have worked.
Sadly, one layer later, I've got an air print, as filament stopped being fed. Neither me nor the extruder could move the PETG filament in either direction, so I've taken apart the heatblock and found the PTFE tube to be cooked and PETG to have formed a blob that would not let it enter the metal heatblock.
I have replaced the PTFE tube, cleaned the nozzle, put it all together (thanks a million for an easy to follow guide, I would not have gotten the tension right otherwise). Recalculated the print head position again, manually homed, edited the gcode, this time. Unfortunately, the second restart went worse and some parts detached, so I'll have to do some welding, to get at sufficient structural integrity. My question is:
Is there a way to avoid this? When I lose power for a long period (there was no storm and there was no power outage in a long time so this was unexpected), the heatbrake fan stops, I can't easily cool it with anything else, since there is no power and it seems, that on a sudden power loss, damage to the system is assured, the heat will creep up the heaterblock and for any high temp filament, damage will occur.
Is the best solution to quickly disassemble the heaterblock? Or is it warranted to have a charged battery, 12V fan and zip ties always close to quickly cool it? Or is it just the PTFE tube that goes toast, so its enough to just have a replacement on hand and add it as another step needed for restarting the print and always assume the PTFE tube bit the dust and the filament formed a blob? Or should I have an UPS? If so, should it be one that can stop the printer gracefully, probably through octoprint? What capacity should be sufficient?
Also, is there a way to also get the original mesh bed leveling info back into the printer? On larger prints, the nozzle always drags in some places and has too much of a gap in others, at least I can see that the mesh bed leveling has a major effect.
TLDR: On power loss, heats creeps up and damages PTFE tube, what counter measures are there?
RE:
I might suggest a UPS, seriously. I have them on both printers, and in one case it kept the print going until we had the generator spun up and on line.
RE: how to save hotend PTFE tube in power outage
I might suggest a UPS, seriously. I have them on both printers, and in one case it kept the print going until we had the generator spun up and on line.
An UPS is definitely something I'm considering, but my trouble is, that I'm usually nowhere near the printer, while it is operating and I have no generator that could kick in automatically, so an UPS would just provide a short buffer and result in the same damage, just some minutes later. It would be cool if there was a practical way to have an UPS send a signal to a printer to gracefully cool down and turn off and maybe even save its state. Darn, I have no idea if there is a feasible way to do this with raspberry Pi and Octoprint.
RE: how to save hotend PTFE tube in power outage
With the MK3 series, with a power failure, it has enough power left to raise the head and save the state. The print can be resumed, although I've never had to do it or tried it.
RE: how to save hotend PTFE tube in power outage
With the MK3 series, with a power failure, it has enough power left to raise the head and save the state. The print can be resumed, although I've never had to do it or tried it.
I mean, if I'm present, I can turn of the heatbed, which takes the most power, and then there should be enough power to pause the print, cool down the hotend. I have honestly never tried to pause and resume the print through a power cycle. Ofc, that wouldn't even be necessary if I then switch the UPS over to a generator, similar to how you've solved the situation in the link, but all of this requires me to be present and then I'm almost thinking, that a 12V battery, 12V fan an zip ties and simply rising the Z axis by hand win on simplicity, but maybe that is way to crude solution 🤪 ?
RE: how to save hotend PTFE tube in power outage
Of course UPS is the way to go but I've had quite a few power outages that even the UPS wasn't able to survive and I've never seen the PTFE tube getting cooked. And I would certainly not expect that with PETG temperature. Maybe there's something else going on.
Formerly known on this forum as @fuchsr -- until all hell broke loose with the forum software...
RE: how to save hotend PTFE tube in power outage
Of course UPS is the way to go but I've had quite a few power outages that even the UPS wasn't able to survive and I've never seen the PTFE tube getting cooked. And I would certainly not expect that with PETG temperature. Maybe there's something else going on.
That is always a possibility, but it seems pretty clear cut. Printer was working fine, then the power gets cut, printer stops cooling, hotend is fully heated, nozzle is in contact with the still hot partial print, even hot air from the heatbed is hitting it. I mean, that is why we are not supposed to power off the printer until the hotend is at about 50°C. Sadly, I was not at home when the power went off, so no reasonably priced UPS would have helped me in that instance, but it probably still a good idea to have one.
RE:
If you need to print for days on end, get a UPS and an automatic start generator. No matter what you do, a Mini is never going to perfectly stop and resume printing later. You will get some anomaly from leaking filament.
Regards,
Mark