Archive for August 14th, 2011

Reversal Zits: Speed Variations

The Vica Illusion Sculpture provides an interesting data point: Reversal zits aren’t much of a problem at very slow extrusion speeds.

This view shows it lying down, with focus on the the zits along facing edges of the columns.

Vica Illusion - Reversal zits

Vica Illusion - Reversal zits

They’re annoying, but not nearly as obvious as the ones on the Pink Panther Woman I examined yesterday.

The nominal speed is 30 mm/s with 100 mm/s moves, but the actual printing speed for those layers works out to maybe 15 mm/s because they’re so small.

In round numbers the extruder runs at half the previous speed, too, which means its internal pressure will be lower. I’m sure that’s a breathtakingly nonlinear process, so it’s not half the pressure.

Low speed isn’t the complete answer, though, because I’ve also done octopodes at 20 mm/s that looked essentially identical to those at 30 mm/s. Yes, it’s nonlinear, but I doubt it falls off a cliff under 15 mm/s.

I set Reversal to 25 rev/min and 125 ms quite some time ago as the smallest values that would eliminate drooling between separate parts. The only thing for it will be to explore the Reversal parameter space again; at least now I know what I’m looking for.

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