Very long print, heat problems (?)
I'm printing a moon model to use as a lamp, and I need some help to make it succeed (check attached image).
By personal preference, I used Slic3r PE, version 1.41.0 on Ubuntu, and the printer uses Octoprint 1.3.9 on a Pi 3. Filament was a white PLA, local brand.
I made the model as big as the printing bed allows, around 195mm across, and chopped a centimetre off the base to put a light socket. From this hole also grow some supports to help the top part of the model, where nearly horizontal. Total estimated print time around 3 full days, the gcode is over 280mb. Around 1.5 days in, the printer got stuck, Octoprint refused to render completely. The printer had a heat warning, and after pressing the knob it resumed immediately, cold nozzle and all. After a while I managed to heat it again through Octoprint, which was still acting weird, and just hoped that the missed layer wouldn't be much of an issue. At that moment I could see a layer shift of around 1mm or less, but decided to just ignore it and hope for the best. Hours later I got what you see in the picture.
Other things I can say:
First I tried printing this on 125% speed (compared to default speed settings), and some hardware/software part was struggling to (probably) keep up with the huge list of small commands. The moon have accurate surface both inside and outside, so it is very irregular and makes lots of small movements very quickly. This apparently caused some buffer to get filled, and the nozzle would stop frequently, to the point that 10-15 minutes later, the printer/Octoprint froze completely, requiring hard reset.
The print above was 100% speed, but I can see on the few last layers (less than 1cm from the heat warning stop, so 14-16 layers before) that there are some blobs of molten plastic "leaking out", suggesting the nozzle sat still for a while, probably like during the 125% speed print. These blobs just show up the in last layers, and not at all before, suggesting that the printer was again starting to struggle to keep up with the print.
You can see the supports on the inside are kinda wobbly but just fine on the outside, which might suggest heat buildup inside the sphere (?)
The fan is working, we even replaced a faulty one some time ago, which lasted us for over a year.
What I think I could do:
Reduce the print speed, say to 75%. It will make the print take even more time... could it increase the chance of other failures?
Instead of rectilinear supports, use rectilinear grid or honeycomb? Would they perform better for tall supports?
If there is heat building up, should I put a house fan blowing mildly on it from the top or something? Significantly reducing print bed temperature after a few layers, if configurable? (no idea if possible) Would this reduce the likelihood of the heat sensor of the printer being triggered again?
Note: I don't want to cut it in parts and glue because that creates a visible mark on the resulting moon when lit from the inside.
I appreciate any tip that you guys can give me. Thanks!
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Veröffentlicht : 15/10/2018 5:30 pm
