I've just done my first print on an Ultimaker 3 Extended and I'm slightly disappointed with the results, so I'm trying to understand how I can do better next time.
My first print
Preparing for printing I naively just dropped the two
stl files into Cura, set the recommended layer height and infill, selected support (defaulting to Extruder 1), deselected adhesion, ran the slice, saved the g-code and started the print running. Luckily the head 1 did have the same PLA AA 0.4 filament that Cura assumed.
When the print finished, I stripped out the support structures, cleaning out the hollow, and cleaning off lots of stringy loose filaments between the lower support and the bottom edge of the print.
Even after cleaning up though, the overhanging structure above the support structure turned out to be very rough with many individual filaments visible and in irregular positions, rather than the nice concentric lines in the slice.
My first attempt to optimise the print
Looking at the completed print I realised that there would have been only a fraction of the support structure, and probably clean edges, if the part had been oriented as a
d rather than as a
p (the rough surface being the bottom of the
I re-ran the slice in
d orientation and that saved 10 minutes of print time, and a 100 mm of filament, so I know I'll definitely need to look out for that in the future. I can also see how that would fix the problem with the external overhang separating out into loose threads, since that face would no longer be an overhang.
Trying to add water soluble supports
After the first fix, I wondered what I could do with the second extruder and realised that it was filled with water soluble PVA filament. This made me wonder if this would have helped with the internal overhang.
I Configured Extruder 2 as PVA BB 0.4 and selected Extruder 2 for the support structures and re-ran the slice.
I was surprised that the it was now taking 40 minutes longer and using almost 470 mm more filament!
Looking at the slices, Cura had created a huge PVA scaffolding on the outside of the print, leaving the inside, where the previous PLA support had been, completely empty:
This was not what I was expecting.
Why didn't the slicing algorithm place PVA support structures inside the overhang, in the same way as it placed the PLA support structures?
What is the reason for the external scaffolding, and how does it help support the internal overhang, which now has no internal support at all?
Is the behaviour I expected possible, advisable or configurable in Cura? If so, what options should I be looking at, if not is there other software that does support this?