I did a test run with the new nozzle and the shielding gas system and homing + probing works as good as before.
Unfortunately it solved none of the problems that I have at the moment. It's like before. Whether I do use shielding gas or not seems to have no effect on the reliability of the printing progress, but it doesn't hurt to have the ability to use it. Maybe if everything else works it can lead to better part quality.
The top 3 problems that causes the print to fail are:
75% of failed prints:
Wire got stuck in the nozzle
20% of failed prints:
"Exruded" material reached the hight of the nozzle and the toolhead crashed into it. (Overextrusion, uneven layer hight)
5% of failed prints:
Wire don't stuck to the buildplate (Too less heat)
I think the last two problems can be solved via the settings and by solving the first problem which is a hardware problem.
The wire get stuck in the nozzle whenever it looses its electrical connection to the buildplate while the heat reaches into the nozzle. When that happens the melted wire in the nozzle cools down in a fraction of a second and because the nozzle itself is not heated but the wire instead is, it gets stuck.
But in most cases it doesn't stick very strong in the nozzle. Sometimes the feeder motor is able to push the deformed wire out so that the print continues until it get stuck stronger what leads to a failed print.
When that happens I have to release the bowden tube from the toolhead and push it back about 10cm so that I can grab the wire with pliers. Then I can push the wire with low force in the direction of the nozzle to get it out for the next printing attempt.
If I could find a way to prevent the wire from getting stuck it would be a huge increase in reliability for the printing progress.
Maybe I could use a direct drive system or a Nema 23 motor for the extruder....
Should I just use a stronger feeder system?
I put the feeder on top of the toolhead to get a "direct extruder setup".
It helped a bit. The wire got stuck fewer times as before and if it got stuck it broke itself free after a short time.