Hello, thank you for your help.
I do not feel offended at all, even if I am familiar with many ideas that you would give me to help.
I can't hear any problems with the filament at that speed, it's not breaking or sounding like scrubbing, I think the direct extruder can handle that speed.
I understand the idea behind retracting too fast and maybe sucking air back into the nozzle, but not at this low amount of filament. My understanding is that the distance is the filament length, 4mm is not that much. but I will try and reduce the speed. (it's a direct extruder, I think I could reduce the length to 2mm, resulting in less pressure change, also worth a try...).
On the other hand, the printer prints at max 300mm/s and would give an acceptable quality of 0.3mm layer height for larger parts. And as you can see from my first prints, the quality is great at 200mm/s with 0.2mm layer height, except for the thin walls. I have reduced the wall speed to 150.... maybe I can reduce that too.
But the problem doesn't seem to be here, because the "blob" isn't created during printing, as I observed, the extra filament is extruded right at the layer change and at the beginning of the first layer line.
I printed a test part at reduced speed... (not the best timing that my filament runs out...)
min layer time: 6->12s
min speed 50mm/s
retract distance 4->2mm
retract speed 120->60mm/s
printspeed 200->100mm/s
i know i should change less values step by step... if something changes and leads to better quality, i would go step by step. but i think the problem is in a totally different part.
this is the result: nothing changed... still watched the same issue, on the thin walls the extra amount came out of the nozzle at layer change. There is no problem with the mid part where i got infill...
only the reduced inner wall flow results in good quality at this thin walls (thin... i mean, it's measured 1.2 mm thickness with 3 walls printed at 3.8mm line width)
One idea, it could be the problem of size measurement and gcode calculation:
original stl file: wall thickness 1.5mm, meassured 1.2mm ...
cura setting: 0.38mm line width. rounded to = 3 lines...
2 outer line and 1 inner line. the inner line need's to extrude more filament, like we can watch in cura:
in a perfect condition the inner wall needs to be 0.74 mm width...
second setting: even with wall thickness: 0.74mm... (2 times line width) this should be 1.48mm i couldn't get a wall print with 4 lines?! i would like to edjust the model/settings to get a testprint with optimized walls... any ideas?`(did i missed something?)
The 50mm/s above results from the minimum layer time of 6s and the speed of 50.
Could be that my middle layers also print in an adjusted time....
It would be nice to see the layer time in Cura.... Feature Request (might not be that problematic, even an approximate seconds would be nice to see if the minimum shift time was reached or not...).
I don't think cooling is the problem:
It's that the nozzle changed layer, you can see the extra amount of filament coming out of the nozzle and a blob of filament being printed, I observed that and came pretty close to the result of a wider "V" shape of the problems on each higher layer because the extra amount is always more with each layer and scrubbed to the sides.