In my opinion you should stay below 0.24, 0.32, 0.4mm layer height as the E3D cannot keep up at normal printing speeds (40 to 60 mm/s) with the 0.8mm nozle. You will have to keep the NGEN very hot so that it will not encounter viscosity resistance. However, at that temperature you will be outside of the recommended heat range only to create other printing problems (stringing, blobbing, layer shifting etc). Just to make sure that your extruder thermistor is doing its job right I would do a PID auto-tune in command line. You could have a bad thermistor causing all kinds of issues. I would start from there to make sure there is no mechanical or electrical issues and then focus on printing speeds and layer height. You do not have to go into Marlin to do this, but you can do it live in command prompt and then store all the values in EEPROM with a M500 command. Are you familiar how to do this? If not, I can explain step by step on how to do it.
"I tried to mount the soc but it cant grab the heatblock, I had to modify it a bit, hopefully it will stay.. we'll see"
Yah the sock does not want to stay in place. E3D messed up with the design of this particular part. I used a thin metal wire to wrap it around to keep it in place. Actually if you look closely a the picture above of the first layer adhesion you will notice how I quickly wrapped a wire around the silicone boot that is over the heater block. It worked for me.
"I have some skipping happening but at the exact same two positions during the layers each time, and it has no effect if i print at 220 or 270 degrees, nor if I print at 20mm/s or 50mm/s. "
It is hard to know what is going on without seeing it from up close. I would start by looking at any mechanical issues first. For example, the Z axis lead screw for bends, wobble or misalignment. Can you move now the Z axis by doing a "move axis", select "Z", and then 10mm movement? See if it will go all the way to the top without any stopping, sticking, clicking, skiping or any other mechanical issues. That would be a good place to start.
If the mechanical motion checks out fine then, it could be that the model might have issues, for non manifold surfaces, bad mesh areas etc. Have you tried checking for bad model areas? I have had that happen to me in the past and it drove me insane only to realize it was the model. Have you ever used Netfabb? It is a free for download and use. It has some limitations as a free version, but the free options are good enough to fix and repair models. I use it most of the time to check things prior to using Simplify3D to slice my models.
Another issue I have come across in the past was that my model was too tall in respects to its width. That is no problem, but you have to compensate in creating a good fist layer adhesion for rigidity. Otherwise as the model gets taller the center of gravity of the model shifts upwards causing extra wobble only to have the print head miss its intended layer position. The printing results show as layer misalignment, air printing, and in a worst case the head knocks-off the model from the print bed. In cases like that I typically will use two layer of an attached brim and about 15 perimeters. That creates extra adhesion and stability. It has helped me any way.
Check also your belt tension on your heated bed. Some times the Y axis belt can slip one tooth causing layer shifting.
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