Each time when I believe everything is under control a new problem is comming up.
When printing the object below,
at some height the nozzle is touching the object, resulting in broken legs, movement of
the whole object or loosing steps in X- or Y-direction. After some observation it could
be observed that the nozzle is lifted up a bit when the extruder is pulling filament
from the spool. In particular when the filament reaches the end rather large forces
are needed the feed the extruder. As a result of the temporarily uplift the height
of the supplied filament becomes too much, which is touched by the nozzle in a later stage.
Probably also the more steep shape of the nozzle of the E3D-v6 makes the printer more sensitive
for this problem. This problem can be reduced (some upheave by torsion is still possible) by a
second leadscrew to stabilize the beam which holds the extruder. However, this is a rather
complicated and expensive modification. A more simpel and cheaper solution is shown below.
In this design the free end of the beam is forced to follow the motion imposed by the leadscrew
by using steel cables and pulleys. Now the beam is sufficient ridged to resist the force needed to
pull the filament from the spool.
some more detailed photagraphs can be found here (at the end of the album): myalbum.com/album/LxWnvUAlFVTN