The April puzzler is another print quality mystery. Take a look at the below pictures of an oversized auger screw originally designed for an automated pet feeder. On one side of the auger there is a blemish in the print yet from another view the print shows an excellent surface finish. What is causing the poor print quality on one spot only? Reply with your answer below and the first correct answer will receive a 5lb spool of PLA. Good Luck!
P.S. The correct answer should include the two factors, that when combined, resulted in the above imperfection.
Looks like a potential thermal problem - perhaps the printer only has a single cooling fan (blowing from the 'good' side). The imperfections (mid-height and top) are both 180 degrees from the start/stop position (seam), but the problem with the print may be caused by the orientation of the infill (just not quite clear in my mind how/if that relates to the seam location with respect to the print quality).
That's all I've got after an exhaustive 5 minutes of thought. Cool print, though.
Hey Patrick,
You are correct that it is a thermal issue and there was insufficient cooling but why did it not happen along that entire side from top to bottom?
It's happening on the outer extents of the overhang (thin sections/corners more prone to thermal error) and was printed without support - but I haven't done enough to know the magnitude of thermal effects on overhangs. I'm also wondering if the orientation of the infill could be a factor - but I haven't quite sussed that out.
Uneven cooling seems to be an obvious factor factor, though you could also see this from a machine using platform tilt compensation ("auto-leveling") or just one with the extruder mounted crookedly or a damaged nozzle, because that could result in the overhang angle (which is properly measured relative to the plane of the of the nozzle, rather than relative to the layers or relative to gravity, though these control second-order effects) that is greater on one side than on the other, as if the object was printed with its axis at an angle.
A more subtle factor is that as the helix extends out from the center, the overhang angle is increasing. A helix with a finite pitch wrapped around an infinitely thin core is perfectly parallel to the axis (vertical), while a helix with a finite pitch wrapped around an infinitely large core is perfectly perpendicular to the axis (horizontal). Thus the helix goes from nearly vertical to nearly horizontal as its diameter increases, and the overhang angle increases. If you tried to print this with support (depending on the slicer's support threshold), you would only get support around the edge, and you would get none near the core.
Hi whosawhatsis,
I like your observation about the angular differences with respect to the diameter of the helix. Please contact me offline so I can send you a 5lb spool of filament!
Thanks anyway, but more 3mm filament is actually the last thing I need right now. All of my 3mm machines have been converted to 1.75, I'm planning a move and have a bunch of 3mm that I need to get rid of.
To summarize: the winning answer was presented by whosawhatsis stating both reasons.
1) Uneven cooling
2) Steep overhang with no support
Great job to everyone and keep an eye out for an improved 360 degree cooling feature for the GB3 hot end to give even better printing capabilities!