Bridging is one of the poorest function of S3D and improvement thousend times requested.
Live with it or help yourself.
I help myself using Slic3r and I try to help us all by posting a "reproducible test case". Fixing a bug when you have a reproducible test case is usually simple; always lot simpler then when you don't have a reproducible test case.
brian442 wrote:Looking more closely at your STL file, I think the issue is that there actually isn't anything to even bridge between!
If you look at the code produced by the slic3r you see that it can be done. Also I can snap a picture of the printed part that came out perfectly (and it's ABS so not a material as easy to bridge as PLA) so you can see no loose wires at all - perfect strong bridge.
Also, I printed few versions of the same object with slightly different overall dimensions (height and width) but with identical design and walls with identical width and that "ledge" with identical size and Simplify3D sliced it properly and printed "almost ok". "Almost ok" because it prints perimeters as perimeters and not as bridge so there were 2 loose wires (perimeters) on the bridge but everything else was perfect. The way it calculates it now is impossible to print.
If you look at the top-down view, the region where you are doing the infill has absolutely zero support below it.
That's the point of bridging - bridging a gap - no support underneath. There are 2 parallel walls between whom you can print a proper bridge. It would be better if those walls are thicker then 1.8mm but it is enough. It was enough for the same part for Simplify3D with slightly changed object (the bridging part was not touched) and it's enough for Slic3r. Bridging is a real thing, it works, and it's often required
for a proper print. Support is good to have, also often required, but in this case bridging is a better option. Adding support underneath it to solve Simplify3D bug is just not solution.
brian442 wrote: There's no foundation to even bridge between.
?! there is a wall on one side, and wall on other side. A classic bridge, you anchor line on one side, run a line from one side to the other and anchor line on other side. Just like Slic3r did, just like Simplify3D did for that same object if you change things "a bit". What "foundations" are you talking about. This is a clear bug in Simplify3D, nothing else.
brian442 wrote: With that being the case, I would actually PREFER that it goes in this shorter direction, since that is much more likely to succeed if there is absolutely nothing below it to support it.
How can it succeed ?! you go from edge to "nowhere" and back and except filament to? levitate?
You think you are doing a short bridge between wall and that hanging perimeter? That's the core
of the bug. Simplify3D don't understand that perimeter is a bridge too and in this case it printed perimeter across the walls. This perimeter will fall down as it's not printed using bridging settings. Then Simplify3D calculates the bridge and sees that perimeter (that already fell down) as "solid edge" to attach bridge to and it bridges using wrong direction. So the core bug for most bridging issues I seen is that Simplify3D prints perimeter on the bridge as perimeter and not bridge and then calculates that the perimeter printed is "solid" that bridge can attach to. Properly printing the perimeter on the bridge would most likely solve most of the bridging issues of Simplify3D
brian442 wrote: So I for one prefer the way it works in your original screenshot, and I'm honestly not sure why the software would ever choose to go the direction you are showing, since again, there's nothing below it for those long extrusions to grab onto.
what is it grabbing on to when doing short extrusion?