Archive for March 16th, 2011
Printing those fairing mounting plates gave me an opportunity to explore the Oozebane parameter space. I wasn’t quite sure how it would work and now I’m certain that it can’t.
Here’s the joint at the start/end of the perimeter extrusion around one of the plates, with Oozebane set for a 4 mm early shutdown:
You’re looking straight down at three edges (bottom = 2 layers, middle & top = 3 layers), but the shadow obscures the vertical faces; they’re firmly joined. The nozzle enters the picture from the left, slows and stops at the joint, then departs for another location.
The turd appears on the far side of this picture, just above the left hole:
Here’s the same joint, but with Oozebane turned off:
Ah: layer thickness 0.3 mm, w/t=1.7 → width =0.56 mm, 45 mm/s feed, 255 PWM flow.
As nearly as I can tell, Oozebane can’t possibly work the way it’s currently defined, at least for the DC extruder on my Thing-O-Matic. The problem is that Oozebane simultaneously shuts off the extruder and slows the feed rate, but the pressure on the molten plastic inside the extruder continues to force it out at about the same rate for quite some time.
Thus, with the feed rate reduced to some unknown (and unprogrammable) value and the flow continuing at the original rate, each thread endpoint accumulates an oversized turd.
Maybe Oozebane works for somebody else, but a stepper extruder is the right solution…