PLA is stuck.
I tried to heatup to 250° (or even 260°), and then pull hard => no effect. Then I cut the filament flush (see picture), and pushed with high force using a hex key => no effect. Now it’s hopelessly stuck 
Any idea how to resolve that clog?
When you were heating the nozzle, did you unplug the cooling fan?
The hotend was not mounted, while heating. The cooling-fan was on.
Is that the trick: Unplug the fan? (and burn my finger 
) … I’ll try …
Yes, you want the aluminum heatsink to heat up and soften the filament. Make sure you wait 5-10 minute after the nozzle reaches temperature for the heat to travel up.
Assuming you don’t have any other printers but if you do this Clog Pusher works pretty good to keep your fingers from being burned.
Are you just trying to remove the cut filament? If so, start a new print without the AMS and once the purge is completely through, do the process for a cold pull.
If you are just trying to remove the cut filament, I’m not sure there is a reason to even do that. The printer is designed to cut the filament like that and just pick up from there on the next print.
If you are having clog issues while printing, that’s different.
Wow, this clog-pusher would have been a great helper. And “yes” - I even had another printer available - but some people need it the hard way:
I was able to resolve the clog: I’ve unplugged the fan, heated up to 250°, and waited until I burned my finger on the heat-sink. Then the flush-cut filament was magically moving backwards (probably due to some expanding vapor), and I was able to pull out a 15 mm long piece of solid PLA (not molten at all). Then I tried to push in a new piece of filament, but it hit something rock-solid - could hear the touching noise - nozzle still clogged. Then I’ve pushed a 0.4 mm needle from the tip of the nozzle back up into the hotend. This also ended with a hard stop, hitting something almost as solid. I’ve repeated that procedure several times always changing the temperature, and suddenly the needle found some path through the whole hotend. That was the final breakthrough - finished the cleanup with a cold-pull. 
Still wondering, what that rock-solid stuff was. I didn’t find any foreign materials (no metal-pieces) in the molten PLA-mess. Can PLA crystallize into some solid high-temperature-resistant structure?
Anyway, many thanks for your support!
Glad you got it sorted out.
For future reference, the clog pusher won’t really help.
Heat up the hotend to 250 or so and get a small Allen key, 1.5mm or so - smaller than 1.75mm, heat it up (I use a small butane torch) and push it into the top of the filament a few mm and let it set for a few seconds.
Once set, give it a slight twist and the piece will pull out easily.
This is also the method BBL recommends.
I believe this occurs because the cutting blade gets blunt and pushes the filament across before actually cutting through, which leaves it slightly wider and not flush at the top and then it won’t fit through the extruder hole easily.
I don’t think PLA can crystalize significantly, but you can anneal it to a more crystalline makeup. But I’m pretty sure that wouldn’t survive 200C + though.
It makes sense you pulled out a small un-molten piece of PLA, the upper side of the hot-end feed should never get more temp than 60C (and ideally much lower). When that does happen you are in for a tough time with clogs.
My guess on the hard stop was likely the nozzle itself. Could be a burr or bad machining.
Here is the full story:
I was printing 2 objects sequentially: the first object with PCTG@240°C, the second object with PLA@210°C. The print of the 1st object succeeded, but after changing the filament for the 2nd object, the PLA must have gotten soft inside the extruder. The print of the 2nd object failed right after first layer inspection. I aborted the print, wanted to unload the filament, and then the filament cutter got stuck - it didn’t spring back, and the printer showed an error message. The wedge-shaped cutter was pressing the soft PLA into Extruder case and into the Hotend, and then everything cooled down with the PLA firmly forged into all the parts (double-clog). Initially I just realized the Hotend-clog - the actually posted topic.
The extruder-clog was at least as tough to resolve: the PLA was stuck like a rivet! After disassembling the whole print-head, I used a 1.5 mm steel pin to hammer the PLA out of the extruder.
Finally I started another print, and the printer did show an error about an “abnormal cooling fan speed”. At some point the Tacho-Wire of the Heater-Cooling-Fan did also break. What an odyssey!
Here some pictures of evidence:
Check your extruder gears. I accidentally put the regular gears back in when cleaning the extruder once and printed about 1/2 a kg of filled nylon. That nozzle was so clogged with metal it was insane. Gears were absolutely shredded from the cf.
