Been printing that logo for the past 2 days tuning the printer.
Mixer speed was gradually increased.
Today I turned it way up...
It turns out you can print *really* fast with an impeller driven print head even with a small nozzle and a low layer height.
I re-sliced my object and turned everything up. That wasn't maxing it out, so I also had my feed-rate at 150% and I was still not stripping my filament. Converting velocity extrusion back to normal E numbers still eludes me, but just grabbing it, I was pushing about 7/8in per second to a .35mm (.4mm measured dia, after die swell) nozzle.
About 20 minutes into my third, large print running it like this, the impeller motor started to loose speed. I knew right away what had happened. The seal had eaten itself.
I'm assuming the increased pressure to the nozzle caused more force on the seal. When I took it apart for a postmortem, the seal was completely gone.
It was awesome while it lasted..
Edit: On later inspection I found the seal in the mass of leaked plastic encasing my spring/thrust bearing. It had extruded itself through the gap around my mixer shaft and was now a long ribbon.
Extruding shaft seals is a problem I had already solved previously, but I had not needed to implement yet for this version.
Back when destroying shaft seals was commonplace, I also gave the plastic a better place to go than into my bearing. I'll be bringing that design back as well.
Perhaps I can keep some of this new found speed..