Today, I spent a bit of time cleaning out the hot end of my Sumpod 3d printer. I put everything back together making sure I was really pushing home the PTFE tube. Unfortunately prints are still messed up by intermittent jamming.
I wondered if perhaps the jamming was corresponding to the natural temperature oscillations of the heating process. I did several prints at different temperatures (195'C, 200'C and 205'C) and videoed the process with the temperature reading visible on the LCD. The good news is that the best print occurred with the set point at 200'C which was the temperature I was using. The bad news is that the intermittent jamming occur-ed with all prints and the video showed that the jamming wasn't directly related to the temperature variations.
The 200'C print started very well:
but then on the third layer there is a trough where the filament jammed temporarily:
The intermittent jamming continued right up to the top layer but there were still periods of good extrusion:
While cleaning the hot end, I noticed that the Bowden tube was warped:
I need to think about what caused this.
My next steps are:
1) replacing the Bowden tube with a fresh piece,
2) cleaning the hot end again to make sure there is no old filament around the interface between the nozzle and PTFE tube, and
3) Add a bit of lint-free cloth before the extruder to clean the filament.
On a more positive note, I attempted something like Stohn's bed levelling mechanism which worked very well and was significantly easier to control than the squashed blutack I was previously using.