The new extruder is working! It is not ready yet, but I can show the first picture.
The extruder is mounted on a new carriage built in the same way as the previous carriage. I would like to improve it later still, because I needed 2 sets of aluminium strips when one should have been enough, but it works ok like this. The extruder is kept down by gravity only.
PLA. More information to follow.