Archive for September 26th, 2011
While cranking out some Tux Cookie Cutters, I varied the Reversal settings to see what effect they’d have on a single object with a smooth perimeter. I’d previously settled on 25 rpm for 125 ms with no early action, so this series tests three different times with early action turned on.
Position 1, where the perimeter threads join. Yes, I have Jitter activated and cranked up to something like 10, but it obviously has no effect on this object:
Position 2, where the nozzle enters from the outside to start a new thread. The snot hanging off the end makes for an ugly wad:
Position 3, another nozzle entry point:
Early Reversal action simply doesn’t work well. With retraction times sufficient to prevent drooling, stopping the extruder before the end of the thread produces unacceptable gaps and starting it before reaching the thread produces hanging snots when the nozzle passes over an existing wall.
Shorter retraction times produce strands all over the object, because the extruder still contains pressurized plastic and drools.
I’d previously discovered, although I didn’t write up, that unbalanced Reversal times didn’t provide any benefit: inhale and exhale times must be essentially equal to prevent either starving the first part of each thread or serious drooling. So there’s really only one degree of freedom: the total volume of plastic = rpm x duration.
Perhaps having separate early action times would help: adjust the shutdown and startup delay times independently of the total Reversal inhale/exhale time. Right now, those delays are simply the inhale/exhale times, evidently assuming clean cutoffs and startups, which obviously isn’t the case.
And, alas, the Reversal Threshold bug remains unfixed, so you (well, I) can’t tell Reversal to not operate across short motions like the end of one thread and the not-quite-adjacent start of the next.