Gap Between inner and outer perimeters on thin components.

[JohnnyRobot]

Hey Everybody,

I'm getting this weird gap between the inner and outer perimeter on thin walls.

the wall of the tube in this photo is 1mm wide. I would expect to see 3 outline perimeter shells.



Nozzle diameter @ .35
Extrusion multiplier @ .94
I have my extrusion width set to Auto @ .45
Outline/perimeter shells 3

When I adjust the extrusion multiplier I still have the gap, it's just a little bit smaller. The part is still weak.

Anyway to get S3D to fill that in with another outline?

[JohnnyRobot]

I can get it to work if I manually set extrusion width to .35

Any reason why "auto" calculates .42? should I be using auto?

[jimc]

This is quite a common issue and should be taken into account on every print or when you donyour modeling. If your wall is 1mm wide there isnt room for 4 extrusions....2 outer 2 inner. You need to make your walls thicker when you model or tweak your ext width to make it fit. S3d wont do 3 extrusions widths. Remember a single perimeter wall would be 2 extrusions. One inner and one outer like you have in the pic. 2 walls would be 4 extrusions and so on.

[jsc]

Jim, I believe S3D will use an odd number perimeters if you specify enough perimeters, but I wouldn't bet on it, and don't want to test it at the moment. You may well be right.

But Jim is right in that it won't try to stuff a thread where there isn't enough space for one. Regarding auto, it calculates an appropriate extrusion width given your nozzle size and layer height; width to thickness ratio should be 1.8 or greater, and all else equal, higher is better.

If you have calculated your extrusion width properly and it still isn't giving you a solid fill, the problem may be that the gap may not be exactly one extrusion width wide everywhere, due to faceting or other geometric issue.

I like to use an explicit setting of 0.4mm extrusion width, as it makes thin walls easier to design for.

[JohnnyRobot]

I usually take this into account when designing. Unfortunately, this component's tolerance is pretty tight.

Hopefully the mating components will still fit at if I print at .35 extrusion width.

Thanks

[jimc]

what will happen is the part may fit but the piece will be weak. you are better off switching to 1 perimeter and upping the extrusion width to .5 or whatever it takes to make that solid.