- Puck.jpg (7.39 KiB) Viewed 7595 times
Looking into the receptacle of the heat break there was filament remaining there from the pre TPE prints (ABS, PETG). Not sure if i did not follow the removal technique diligently enough or if the TPE did not make a good bond with the other material. (pic after digging at the filament a bit)
Took the hot end apart, cleaned up the heat break with acetone and noticed a couple of things.
There were some ridges in the heat break receptacle which may have interfered with seating the Bowden tube.
and the 1.8mm hole (filament path) in the heat break was off centre by 0.2mm to the Bowden tube receptacle bore as well as the heat break threads that go into the Heater block(post remediation pic)...
...so subsequently the heat break 1.8mm hole was offset to the 1.8mm hole in the nozzle, as the two are aligned by the female thread in the heat block.
Cleaned up the Bowden tube receptacle...
...and chamfered the entry to the heat break 1.8mm hole to provide relief where the Bowden tube would override the offset hole. Unfortunately this created a small place for a bulge in the filament to form but could not think of another solution.
Relieved the entry to nozzle where the heat break hole overrides the nozzle.
- Nozzle Relief.png (222.06 KiB) Viewed 7595 times
Polished filament path in nozzle (and heat break) as best i could.
- Nozzle Polish.png (225.41 KiB) Viewed 7595 times
Reassembled hot end, running the heat break as far as possible (constrained by alignment of heater block to fuse) into the heat block in order to try and keep the gaps where the Bowden tube interfaces with the filament path in the heat break within the melt zone. Inserted Bowden tube using the tip from the HE280 FAQ to firmly set the PTC collet. Insertion distance was 45.8mm from top of PTC collet (sitting down on nut) to bottom of heat break receptacle. This was about 3mm more than previous insertion measurement, so one of those ridges may have been hanging upthe Bowden tube, or maybe there was already some trapped filament when previously measured. Finally, removed nozzle and trimmed away Bowden tube exposed from the offset and cleaned up with a drill bit to provide a more gradual path for the filament at the end of the Bowden tube to move over into the filament path in the heat break (couldn't get a decent pic).
Subjectively, there was less resistance to manual extrusion both via pushing filament through by hand with extruder idler disengaged as well as to turning hand wheel and extruder motor driven extrusion was consistent vs previously irregular.
Results (n=1, TPE with hover type extruder, no retract); Printing like a champ, spitting out parts like hotcakes... Print quality much improved and minimal to no ooze post remediation, the latter possibly because backpressure and subsequently filament "accordioning" in Bowden tube is reduced.
