change angle for Top/Bottop?

[herzla 3]

in the images below you see I'm experimenting with overhangs

my current problem is that Cura starts to add Top- and Bottom-Layers on overhangs (the yellow lines in picture 2)

when I set Top- and Bottom-Thickness to Zero I get the better overhangs but top- and bottom layers are missing :~|

 

suggestions? any option to change the min-angle for Top/Bottom?
is there any way in cura to set different settings for different regions on an object? (also wall-thickness would be great to change for areas with extreme overhangs)

[GregValiant 1,141]

If I understand correctly, it isn't precisely "top/bottom" layers that Cura is adding but rather what it refers to as "skin" in the gcode but think of it as an area of 100% Infill.  This Skin Infill will get added on nearly every model with curved sides or angled sides.  As the angle to the base plate approaches 0, the amount of Skin goes up.  Conversely, as the angle approaches 90° the amount of Skin Infill approaches 0.

 

Whether you ask for a specific wall thickness, or ask for a specific number of wall loops (which gives a specific wall thickness) then Cura will look at the model and provide that wall thickness at an angle of 90° (normal) to the angle of the wall. 

It's a function of slicing always being parallel to the build surface.

It's hard to see in my image, but we have a goblet with a constant wall thickness of 3mm.  You can see that a slice taken at Section AA is pretty wide.  The slice taken at Section BB is much narrower.  Section AA would have loops around the outside, and inside.  The "Skin Inill" between them is to make up the wall thickness of the model as it builds up.  Since Section BB is cut at nearly 90° to the part, there would be "none" to "very little" skin infill.

Even in a solid model, if the number of Loops isn't sufficient to give the Wall Thickness you've asked for then Cura adds skins to make up the difference.  I believe that is what you are seeing.

 

[ahoeben 1,886]

You could try setting the "Top/bottom pattern" to "concentric" for this model.

[herzla 3]

here how it looks like with "Top/bottom pattern" set to to "concentric"

"Wall Thickness" is 1.8, "Line Count" is 3 as Nozzle is 0.6

[ahoeben 1,886]

18 minutes ago, herzla said:

here how it looks like with "Top/bottom pattern" set to to "concentric"

And what is the problem with that?

[herzla 3]

I'like to get it look like this while I need "Top&Bottom" at the real top and bottom

[GregValiant 1,141]

Add a support blocker at the top and one at the bottom with both being 0.9 thick and with both configured for Top/Bottom thickness of .9, 0 Walls and 0 Wall thickness.  The top of the upper support blocker will be flush with the top of the model.

 

The most severe angle on my cartoon is much more than on your model.

 

The bottom is in place and there are three walls all the way up

 

 

BUT the loops are too far apart layer-by-layer and are air printing and not connected to the previous layer.  That might resolve itself if there wasn't such a severe angle.  In this case support doesn't help because you are printing unconnected model features for a few layers.

 

AND the top is totally over air.  You can't bridge with Concentric since the extrusions don't hit the walls.

 

Edited June 27, 2021 by GregValiant

[ahoeben 1,886]

47 minutes ago, herzla said:

I'like to get it look like this while I need "Top&Bottom" at the real top and bottom

But the slice with no top & bottom shows you exactly why you need those "top & bottom" layers in the first place. Without them, you get holes. I think the figures by @GregValiant are pretty clear about why.

[herzla 3]

I accept it's a feature, anyway my qustion was how to turn if off

15 minutes ago, ahoeben said:

But the slice with no top & bottom shows you exactly why you need those "top & bottom" layers in the first place. Without them, you get holes. I think the figures by @GregValiant are pretty clear about why.

with my settings of layer-width and height I don't get holes
as my walls bevome better without this extra scin-infill I think this is no part to discuss about, my model was nothing but a sample..
 

37 minutes ago, GregValiant said:

Add a support blocker at the top and one at the bottom with both being 0.9 thick and with both configured for Top/Bottom thickness of .9, 0 Walls and 0 Wall thickness.  The top of the upper support blocker will be flush with the top of the model.

I'll give the support blocker a try, just I never saw the option to change options for the support-blocker?
sometimes I'm dreaming of defining different options for a region - but this feature does not exist?

[GregValiant 1,141]

Add a support blocker.  You can move and scale it like any model.  The tool above the Support Blocker tool is called "Per Model Settings" and you can select "Modify Settings for Overlaps".  In the dialog there are two options for "Infill Mesh" and for "Cutting Mesh".  I'll let you play to figure the difference.  A support blocker can be configured to "define different options for a region".

Edited June 27, 2021 by GregValiant

[herzla 3]

i already played with this settings but the "support blocker" always get's printed here

so you mean the support-blocker would need to follow the curve or something like that?

[GregValiant 1,141]

Support blockers (modifier meshes) can be moved and scaled to precise sizes.  The attached 3mf file has a blocker 110 x 110 x .9 located at 0,0,0.  It's just a cartoon and not a real model but you should get the idea.

Drawing2A.3mf