Hello all,
I have noticed that a lot of my prints that have some thin (1-2mm) walls will come out hollow, at least if I don't catch them in the print preview. Even when I set my infill to 100% and perimeters to 1 it still happens. I kind of understand why this happens, extrusion width is .40 and a wall is 1mm thick.... you can't really get 1mm from .4 so it just makes it hollow. I am sure one of you can explain it way better but I do have a simplistic understanding of what is causing it, what I would like to know is how do you guys usually fix this issue.
Some ways I "fix" this issue is by....
1. lowering my extrusion width, for example, instead of .40 I will go down to .37 or .35 and that sometimes solves it.
2. change perimeters from 1 to 2 or from 2 to 1... heck, I did 3 perimeters one time and that worked!
3. change infill settings drastically, this sometimes helps, sometimes it doesn't effect it at all.
4. I just figured this one out today but it will only work on something that needs 100% infill or if you can arrange the part so that your thin wall is at the top or bottom of the print you can set your number of top (or bottom) layers much higher, for example I am printing a small part right now I and tried all my other methods without luck so I set my number of top solid layers to 20 and this allowed the piece to print solid!
I am sure a lot of these tricks can have an effect on the overall dimensions of the finished part so you might want to keep that in mind.
I know there is a "Thin wall behavior" section under the advanced tab but I never had any luck playing with the setting, mainly because I have no idea what those settings really do!
Share your tips on thin walls! I print a lot of them!
Thanks guys!
Brandon
S3D and thin walls coming out hollow
Re: S3D and thin walls coming out hollow
Actually, you've tried some that i never would have thought of! 
I have occasionally reduced the extrusion width, taking the width down to 0.37mm is usually enough to trigger that infill. Or i sometimes have redesigned the file with a specific layer width of 0.4mm in mind (In other words, if i created the file, I either design it with a wall that is 1.2 mm wide or 0.8mm wide, instead of 1.0 mm wide.)
If i've done a design that has tight corners and i want the infill to fill up as much space as possible solidly between the outline areas, you can use those Thin Wall settings:
Uncheck the option that says Only Use Perimeters for Thin Walls.
Check the option that says Allow Gap Fill When Necessary.
Allowed Perimeter Overlap - set to Zero %.
I have no idea if it impacts actual thin walls though. You might try the settings and see. The dropping the middle row (very good description, by the way) is exactly that. S3D can't fit it in so it just drops it. It's the nature of that particular slicing software - we have to work around it.
I have occasionally reduced the extrusion width, taking the width down to 0.37mm is usually enough to trigger that infill. Or i sometimes have redesigned the file with a specific layer width of 0.4mm in mind (In other words, if i created the file, I either design it with a wall that is 1.2 mm wide or 0.8mm wide, instead of 1.0 mm wide.)
If i've done a design that has tight corners and i want the infill to fill up as much space as possible solidly between the outline areas, you can use those Thin Wall settings:
Uncheck the option that says Only Use Perimeters for Thin Walls.
Check the option that says Allow Gap Fill When Necessary.
Allowed Perimeter Overlap - set to Zero %.
I have no idea if it impacts actual thin walls though. You might try the settings and see. The dropping the middle row (very good description, by the way) is exactly that. S3D can't fit it in so it just drops it. It's the nature of that particular slicing software - we have to work around it.