I recently installed a 0.8mm nozzle because I want to print simple parts like sorting boxes faster.
Unfortunately I have massive problems.
At the beginning there is simply not enough filament coming out of the nozzle.
If I reduce the offset, the results get a little better, but then I have the impression that I’m destroying the print bed.
I’ve experimented so much with retraction settings and the like and I just can’t get any further.
For a 0.8mm nozzle, I use speeds that are half of what is most commonly used for a 0.4mm nozzle, so in the 10-12mm/s range. There is also the temp issue; the 0.8 nozzle needs more heat to melt the higher volume of filament flow. With a 0.8 nozzle I use about 10c higher than the temps used for a 0.4.
Linear Advance/K-factor can be calibrated using the following tool…
There are also a few settings in your slicing software that can cause effects like you are seeing, most notably retraction settings (which you say you have already experimented with), and “Combing Mode” (this one you will want to set to “Within Infill”). My retraction setting for printing PLA with a 0.8 nozzle is 1mm@50mm/s.
I’d use “Retraction Extra Prime Amount” - it pushes a bit more plastic into the nozzle as it retracted before, to compensate for oozing and have pressure a bit faster. With my 0.4 mm nozzle I get well along with 0.25 mm³ - with 0.8 you might consider a bit more perhaps - but this is a guess, no experience from my side with larger nozzles.
As some said, make sure your E calibration is right. I had the same problem with it, after E calibration and still having the issue. Ended up being a clog nozzle in combination with the retraction mm amount.
The heating element’s neck (smallest part) can’t accommodate not even 4mm back into it, meanwhile the default when choosing retraction is 5mm, a little more than a millimeter gets stock in there, I decided for a default of 3 and that fixed most of my clogging, purchased 5 extruder and heat element kit, at $9 each, worth the money and getting clogged in the middle of a job and the starting point is no longer a problem for me. Hope this helps you.
Almost forgot to mention, remember that the retraction problem in this case, the nozzle is 0.8 more PLA goes back in it.
I couldn’t import your settings to cura but after watching your videos I think it’s pretty obvious especially in 3369 that there is filament coming out at the start. It looks like it’s not catching on to the bed good/quickly enough. I would say lower the Z offset a bit and maybe raise the temperature… make sure the bed is clean of course…
If that doesn’t help you could experiment with some other settings, for example:
initial layer height
initial layer line width
retraction prime speed