Problem HOTEND
I have a problem with HOTEND. In the moment that the filament arrives at the HOTEND plastic tube inlet the filament locks at the edge of the tube. Even with the extruder gears aligned with the tube. I also used several different tensions on the M3X40 screw that has the tensioning spring to see if the problem was solved but also got no difference.
Just to clarify: I just assembled the MK3S kit and did a few tests and everything went perfectly fine. After these few tests I set up the MMU2S and after that in some (still) test prints I started to have this problem. But when the filament can enter the extruder without pinching the sides, printing works very well. I couldn't test a multi-material print because when the MMU will change the filament it will stick to the side of HOTEND's plastic tube.
RE: Problem HOTEND
Have you tried a cold pull with cleaning filament, to make sure no debris is in the hot end?
I would have said nothing sticks to PTFE - what you are calling the plastic tube. What I call Teflon.
RE: Problem HOTEND
The filament is pinned tightly to the edge of the Teflon and not inside the tube as if it had remaining filament inside preventing passage. The filament hangs just like the picture above.
If you get closer to the picture you can see that the filament can't get into the tube.
RE: Problem HOTEND
I never clip the filament into a needle point ... always worried the sharp tip would dig in somewhere it wasn't supposed to dig in.
RE: Problem HOTEND
Your Bondtech looks centered on the part line. I would physically straighten the filament before insertion. It appears to be a curved segment is exacerbating the problem. I always clip at 60 degrees sharp, but if the filament is curved it will deviate.
This can be improved with a sculpted, longer PTFE tube like those created with https://www.thingiverse.com/thing:3819794
However, that does't do you any good until you can start printing something. So, for now undo the curve of the filament before insertion.
RE: Problem HOTEND
I think I lucked out. When my MK3S upgrade kit arrived the two PTFE tubes that came with the kit were ever so slightly long, and touched the Bondtech gears. Instead of trimming the PTFE down to the "floor" of the Bondtech area (which would have gotten rid of the internal chamfer as supplied), I just carefully trimmed the sides of the top so they no longer quite touched the Bondtech. Sort of a manual trimming similar to the Thingiverse item that guy-k2 referenced.
I have never had a loading problem related to this. (But now that I've publicly stated that I need to watch out...)
See my (limited) designs on:
Printables - https://www.printables.com/@Sembazuru
Thingiverse - https://www.thingiverse.com/Sembazuru/designs