Skeinforge Feed Settings

As part of the general reshuffling, I’ve started running the printer with different feeds for different functions:

  • Travel = 250 mm/s (non-printing!)
  • Basic rate = Infill = 60 mm/s (SF Speed plugin → Feed Rate)
  • Perimeter = 0.33 → 20 mm/s
  • First layer Infill = 0.25 → 15 mm/s
  • First layer Perimeter = 0.15 → 9 mm/s

All of the corresponding Flow rates have the same values, which seems to be the right way to go. In Skeinforge 45, these are all collected in the Speed plugin.

The very slow first layer ensures good adhesion to the Kapton build surface, with the rebuilt HBP now maintaining a very stable 0.25 mm across the whole platform. I’ll try goosing the first layer infill to 20 mm/s and the perimeter to 15 mm/s at some point, but this is entirely tolerable; I’d rather have it Just Work than occasionally come unstuck.

The 20 mm/s perimeter reduces the Extruder Zittage problem, with the 9 mm/s Perimeter on the first layer coming out entirely zit-free. However, the sequential version of Amdahl’s Law applies here: a slow perimeter around a fast infill produces a fairly slow overall layer. Making the infill rather sparse doesn’t help, of course, but overall it’s a win.

This collection of speeds hopelessly confuses Pronterface’s estimated print time calculation; the most amazing prediction reported just under 24 hours for a fairly simple set of objects that took maybe half an hour. A recent gizmo had an estimated time of 4:34 and an actual time of 28:07, off by a factor of 6.2. If Pronterface divides the total filament length by the first speed it finds in the file, it’d be off by a factor of 6.7, so maybe that’s close to what happens under the covers.