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Thanks to those who have already identified the problem with the Bowden tube not seating fully in the heat break or pulling back a bit, that was the first place i looked when jamming occurred while printing TPE. Loosely following the excellent treatise by timskloss for withdrawing jammed filament from the hot end, there was indeed a little "puck" on the end of the filament. .

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. .

Polished filament path in nozzle (and heat break) as best i could. .

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.

all the photos are missing

Sorry about that, checked on a different computer - photos should be up properly now. Was dragging them up from the attachment list but that only worked for the computer that i made the post from. Learn something new everyday day no matter how small and painful it may be...

I need to do this....I thought I had fixed my puck problem but just got lucky for a bit, now I'm pucking constantly and it is really killing my print quality.

It really sucks when your hotend is pucked.

Probably worth taking a look. If the filament hole in your heat break is offset a fair bit as mine was, you should be able to see that just by taking out the nozzle. Examining and removing any debris from the receptacle end is likely the more important part. This will, of course, require disassembling the hot end, which can be done without desoldering provided you can slide the crimp connections on the heater wires a bit. i replaced the two Philip's head screws on the heater block clamp with socket head cap screws (M3 x 10mm stainless) to make future maintenance a little easier.

Also of interest, it may be worth noting that the dimensions of the PTFE Bowden tube can vary a fair bit amongst suppliers. The SeeMeCNC tube i have has an OD of 3.94mm vs 4.06mm and 4.16mm for E3D and RobotDigg tubes respectively. Tube OD might affect the ability to seat the tube fully in a less than perfect receptacle and also how firmly the PTC collet grips the tube.

If you can, you will want to print the little PTC nut wrench before you tear things apart. The instructions recommend backing the nut off two turns but i found that i needed 3 turns to get a solid grip (i.e. not easily release the collet) on the 2.06mm OD tubing. On the extruder end, i have been using this technique to set the collets with 4 or 5 turns but that is with an all plastic (less constraint) John Guest PTC. The risk of getting too aggressive with the HE280 set up is either breaking the collet or not firmly clamping the accelerometer plate to the heat sink. The latter would likely produce a fair amount of "entertainment" (and possibly the utterance of certain words that might rhyme with a certain piece of equipment involved in the game of hockey...).

bruceg wrote:(couldn't get a decent pic)

Ha! Those are excellent photos. Would you share how you took them?

Used a "cheapo" stereomicroscope at around 30x with a 9MP camera on a trinocular port. Between not being organized enough to have built a proper stage for it and still being in kindergarten on the camera software, i was having trouble getting the camera to "look" at the desired region of interest. Nonetheless, it is very handy for old eyes in terms of magnification + depth of field. Here are a couple of pics of single spiral perimeter tubes in Ninjaflex.

Ah, a toy I don't yet have... Thanks for the tips!