BenJackson wrote:Collapsing infill is probably due to not enough shells. I get ok surface results with 2 shells with 0.5mm nozzle and 0.4mm layer heights, but with 0.35mm nozzle and thin layer heights most people use 3 shells. The first "shell" sags into the infill (unavoidably) the second one sags into the first but the 3rd is generally nice and smooth.
That wasn't quite what I meant. I was talking about the sparse infill. I find that as the speed goes up, I have to be very careful about how much the plastic stretches or it breaks and forms random spiky blobs rather than a nice neat grid. I seem to have that under control now, though.
Also, did you mean solid layers? Shells are the perimeters around the object. I use 3 solid layers, and usually have good results by the second. The third gives a dead smooth top surface.