I've got a reprap-based 3d printer from 2014-ish that I've rarely used and has always had the same issue. Eventually during any print, back pressure builds and filament stops extruding. The first time I took it apart a few days ago I found a decent amount of burnt plastic on the heatblocks (dual extrusion machine) and so i have attributed the issue to improper fitting of the heatblock and break. I have cleaned the heatblock, break and nozzle and reseated them a few times:
I screw in the nozzle then unscrew it a turn, then I thread the heatbreak back in. This goes well, the pieces seem to tighten and meet with the expected gap of the heatbreak exposed without any room to tighten further. However, when I turn the machine on and heat it for the last tighten , the heatblock will easily tighten all the way to be flush with the heatsink. The hozzle and the heatbreak never seem to meet at all. I have tried printing like this, but the same issue comes back within 5 mins of printing and the extruder stops.
This printer was made quite a while ago by a small company so documentation is non-existent. It's an e3d-style hotend but quite possibly a clone. The printer has always been like this as far as I remember, but I never bothered to take the fan shroud off and have a go until now. Does this sound indicative of a specific broken component? I've looked every piece of the hotend over and it all looks ok to my eye.
