I’ve been wondering why the columns on the Torture Test printed so badly for all of the slicers when I’ve seen them all do better than that before. I tried a single column with Slic3r 096 which was one of the worst for that section. I also wondered if there might be a problem due to the model coming from Tinkercad, so I printed one column from Tinkercad, and another from Alibre-
They both look pretty good, aside from where I gouged them with my scraper. My concern with Tinkercad was that STLs generated there are typically fairly low resolution. You can make out the increased faceting in the print but it didn’t cause a problem otherwise. I thought there might be a difference due to the bad columns being part of a larger print. I cut out the rest of the model and tried a print of only the column section.
It’s a little better. The misaligned layers seem to be gone, leaving only blobbing and artifacts related to the start and end points of the external perimeters. I had used Tinkercad’s STL import feature to convert the original torture STL to solid, and easily add other elements. There is some decimation that happens in the process and who knows what else, so I decided to compare meshes. This is the original-
The columns start out smooth at the bottom, and become more blobby where the resolution increases. The column with the chamfer shows the pattern as well. In the mesh, the column starts out simple, becomes more complex rising toward the chamfer, then becomes consistent and well ordered after the chamfer. The effect of that change is clearly visible in the print.
I decided to print the original, unaltered Torture Test in Cura and see how much difference the mesh made in the final print.
There is a small improvement, but it isn’t drastic; a few less lines in the columns and a smoother surface on the arch.
Here is a simpler set of columns drawn in Alibre:
It seems as if the columns were all rendered with the same number of faces, but on the smaller columns those faces must be much shorter. It seems that with Slic3r, it begins to have more and more trouble as the mesh gets denser. Here is a KISSlicer print of the same STL:
I also wanted to test perimeter speeds. You can get a much better surface quality by keeping the speed of the outer perimeters low, while letting the inside of the model run faster. I printed the column set in Skeinforge once at 50mm/s like all the other prints, and once with the perimeters at .25mm/s.
This really was a torture test, not just in the features, but also the inconsistent mesh. This exercise wasn’t about finding the best settings and creating the nicest print, but seeing how the slicers perform relative to each other. The torture model happened to test how well each of the slicers dealt with a mesh that was disorganized, and I think KISSlicer handled it with the most grace.
In the next post I will try some owls for a more organic print.