I’m not sure why you say it’s a Cura problem. Did you use the Preview to check the entire model in Cura before sending it to the printer?
Just this morning I started printing another deck umbrella clamp and noticed part of the bottom wasn’t printing. I went back to Cura. In the Prepare window I rotated the bed so I could see the bottom of the model. Sure enough, it was red instead of cyan. I rotated the bed back, then pulled the model up and let it fall back to the bed. I rotated the bed again and, now, the bottom was cyan. I sliced the model again and started printing. It’s going well. Only another 15 hours to go
This is one a shot in the dark but have you checked the screws on on the extruder gear? I recently had an issue of mine coming loose? Wouldn’t explain the breaking but might the extruding and not extruding. If you think Cura is the issue I have you tried another slicer, like Prusaslicer or Ideamaker?
Still sounds like maybe your filament has moisture in it making it brittle. I know you said you keep it in a vacuum bag. I recently had some that was also stored in a humidity controlled environment and it still got brittle. I dried it for 4 hours and it was fine.
I am sure the lid was flat on the bed. After printing 5 layers on both lid and jar bottom, the process was to do a layer on the wall only for the lid, the moved to the jar and printed the full bottom, switched back to the lid and did a layer of the wall only. Then it printed the wall and bottom again of the jar. Then it was through with the jar bottom and from that point only worked on wall until finished ( moving back and forth between the jar and lid of course.), but then started laying down double layers not touching walls in the lid and then layers a layer for 5 times.This was because it started the threads on the lid (the two separate walls. After the 5 bottom layers, it did start to close the walls of the inside thread wall and the outside wall. On the jar at the finish of the jar and start the threads there were the start of two walls which were closed as the threads closed around the outer wall. That was too much said for the skip of one layer of the bottom of the lid. Why the skip of the layer between two sections of 5 layers or why it did more than the 5 bottom layers, I do not know. I also had the number of top layers at 5 also.
I just looked at Cura and found that infill was at 0% This explains my problem with a skipped layer. I think problem solved! Just cannot use the gcode file any more.
OK, you will have to re-slice the model. Not a big deal. However, this whole issue points out a lesson I learned the hard way – never try to print something until it has been carefully checked in Preview. I (now) always run up and down all the layers, zooming in and out on the model, to ensure everything is as I expect it to be. It takes so long to print things, I just don’t think it makes sense to slice-and-print. I would rather slice-preview-then-print.
