Gaps in Infill, but not in perimeters

[Legion_23]

Hello, dear S3D-Community

I´m using Simplify3d for many years now and every now and then, I run into a specific problem: There are some parts which lead to slicing errors. The problem is that sometimes random infill layers are missing, while every other feature type on the same layer is perfectly fine. It looks like this:

The strange thing is that this error moves: When I move the part vertically (Z+-), when I rotate it or sometimes even when I just move it horizontally, the error disappears on one layer and reappiers on a different layer. It even occured that I printed the same stl-file 10 times in one run, where 9 parts were sliced flawless, but 1 part had this slicing defect. It makes obsolutely no sense to me how this can happen. If the STL would be damaged, than rotating or horizontally moving it shouldn´t have any effect.

The stl-file doesn´t seem to have any defects. There are no non-manyfold edges or self intersections detected.
I also tried different slicers, were this error doesn´t happen with the same files.

The factory file is attached here:

Test_geometry_1.factory

(1.86 MiB) Downloaded 589 times

The defect appears on layer 1014.
Could someone try the factory file and check if the error can be recreated? Maybe it has something to do with my system, but if it can be reproduced, it might be a bug.

[S3D-Jason]

If it goes away when you move the model, that sometimes indicates there's a problem area on the mesh that can sometimes be avoided depending on how you slice it. Frequently changing the layer height very slightly (by 0.0001mm) is another way to fix it.

In those cases, many times it can be caused by just very bad triangulations. This part has some triangles with 0.0 or 180.0 degree triangles, meaning they are essentially just straight lines and not a triangle at all! If you have the CAD file for the part, I would recommend trying to re-export it with different settings to create better triangles. Sometimes you can also find apps that will automatically repair those bad triangles by remeshing.

Hope that gives you a few ideas!

[Legion_23]

The file I´ve uploaded is just a snippet of a much larger part which I can´t upload due to it´s size. I just cut it so that I can demonstrate the error here.

The actual part is much larger an has defective infill on ~10+- layers.
I already tried to export the part with different settings, used mesh repairs programs (I used Fusion360), and tried multiple different orientations and positions of the part. I just cannot slice the part without errors.

I simply don´t understand were the problem is: S3D can compute every layer outline without problems. When I slice the part 100% filled with solid layers (9999 top and bottom layers), than there are no gaps. The gaps are only there with infill, which is basically the same operation as a solid layer when I use 100% infill. There is no difference in theory.

So this is clearly a bug with the infill computation in my opinion. Is it using a different, maybe unfixed mesh internally while all other features use a fixed mesh or something?

I sliced the same part with cura, which is a free software, and there are no slicing defects with the same file.
It is very frustrating to see that a free software performing better in this regard than a professional one which costs more than 100€ at the moment.

I love S3D for it´s usability, support creation and slicing speed, but it must be possible to fix this issue.

[Legion_23]

Are there any news regarding this topic? Are you working on the problem?

[S3D-Jason]

My best guess right now was that it was related to the issues that I mentioned with the mesh. Did you try exporting the part again from your CAD program with different settings? Are you able to get this to happen with a different part that doesn't have any mesh issues (no self-intersections, triangles with non-zero angles, etc)?

[Legion_23]

The stl-file which I used for this test has no defects. Neither Simplify3d, nor Fusion360 detect any defects.
I sliced this file with an older S3D-Version (4.1.2), and I couldn´t reproduce the error with this particular file there (while I had errors on other STLs with 4.1.2 as well). So it seems like something regarding the slicing stability has changed from 4.1.2. to 5.1.2 ... for the worse.

My best guess right now was that it was related to the issues that I mentioned with the mesh. Did you try exporting the part again from your CAD program with different settings? Are you able to get this to happen with a different part that doesn't have any mesh issues (no self-intersections, triangles with non-zero angles, etc)?

Sure, I can try to remesh, reposition, reslice STLs dozens of times, waste several hours to find just the right setting, orientation or position to eliminate the slicing error, but I shouldn´t have to.
Other free slicers don´t have this problem, only this premium slicer.

When I slice the part with 9999 top layers instead of 100% Infill, everything is fine:

This clearly shows that the software has a problem with the infill feature.
I tested some other infill patterns than "rectilinear", nothing changes.

[S3D-Jason]

If you aren't able to just re-export the mesh with better settings, there are already several automatic repair modes in Simplify3D to deal with problematic meshes. There's a whole article explaining them here:
https://www.simplify3d.com/resources/ar ... sh-errors/

In particular, I frequently see some parts that work better using Slicing Region Repair Mode > Alternating Fill. The Merge All Boundaries mode can also be useful for really bad files.