Layer Skipping?  

Layer Skipping?

Hello everyone,

recently I upgraded my MK2s to MK2.5s.  While my Mk2s always delivered good prints (user mistakes aside), I havn't succeded in printing something bigger using the Mk2.5s yet.

After the reaches a height of round about 8mm it startes to make some quiet squeking or rubbing noises. Just as if the tip of the nozzle would scratch over the layer. But if i look, there seems to be everthing all right (except the noise). Everything looks like it should, No filament is stuck or clogging the nozzle. But during the print it looks like the printer skips some layers. First only single layers, later on multiple at once. At the end nozzle finally clogs and filament stops extruding. 

The final result looks like this:

I tried:

• different layer heights
• different filaments
• checked live adjust z
• adjusted x/y axis (calibration says they are perpendicular)
• different printing temperatures 
• adjusted the screw at the extruder idler

Nothing helped. My next step would be to reassemble the extruder hoping to correct a possible mistake. May be the alignment of the gear is wrong. 

Has anyone an idea what could solve my issue? Interesting bit: everything I tried to print under 5mm height succeded without trouble und looks fine.