Some of you may already do this, but for anyone who suffers from this problem, I though I would relate my experience.
I was having problems with filament clogging up my hotend. I searched on the net and it seems to be the most common problem with 3D printers, and most people seem to go through the chore of letting the hotend clog up and then stripping things apart to remove the solidified gunk using pins, drills, boiling water etc etc.
After having multiple clogs up through the Bowden clamp, the easiest way to remove them was to remove the whole PTFE feed tube from the extruder, and drop the coiled tube into a bowl of boiling water. This softens the PLA without melting it. If there is enough protruding from the Bowden clamp then pull on it and it will stretch. Don't pull it right out, just enough so that the stretched part has thinned down the blockage. If there isn't enough poking out, then use a 1mm drill bit and using hand pressure only, twist it into the softened PLA. When the PLA has started to solidify again, slowly pull the drill bit out and it will pull PLA with it.
Then get another length of filament and push it through from the other end. Keep repeating this until the blockage slides out. No damage to the PTFE tubing, and none to the Bowden clamp.
What causes the blockage? Conducted heat travelling back up the filament when the printer is inactive, but the hotend is still at operating temperature. It happens on mine at 185 degrees. The heat simply travels back up the filament, softens it right the way through the Bowden clamp and when printing restarts, solid filament pushes on soft filament, deforms it and any kink solidifies and blocks the feed.
It was driving me nuts, especially as when setting up a printer I was leaving the hotend hot while testing. It was a lot of work pulling everything apart.
I solved it by adding Gcode to the end of the print file in Slicr. It moves the print head away from the print, and then extrudes a puddle while the hotend cools down to around 150 degrees. That way cold filament is always going through the hotend, until the hotend has cooled to the point where it isn't melting the filament.
Alternatively, just set the manual 'Extrude' on about 10mm, and keep pressing the screen button until the stepper motor starts to click, that is the point at which the feed is pushing back as the filament is no longer melting in the hotend.
It works for me, and saves me a few headaches.
Rob
