A long time ago and in a galaxy far, far away I tried to print Ninjaflex faster than the recommended 30mm/s and encountered filament jamming out of the side of the extruder body, in the hobbed bolt access window.
I filled in that part of the Flexystruder and finally had time this past weekend to rebuild it.
YMMV, but I’m able to reach speeds of 80-100 mm/s with SemiFlex and NinjaFlex, for a pretty good speed increase over the standard recommended speeds of 30 mm/s, at around 225C for SemiFlex and 230-235C for NinjaFlex. I was previously only able to reach speeds of about 30-40 mm/s before it would start jamming and binding.
flexystruder-filled-access-hole.stl (273 KB)
As always, feel free to try this yourself and see if it works any faster than the original Flexystruder. I’d love to know how this works for you.