How to stop Cura to place skin inside infill

[Lucasss99 0]

Hello,

 

I am facing a problem in Cura where Cura places top and bottom skin between two walls, inside the infill region. This is probably due to the fact that this happens on a sloped 45 degrees wall. Is there a way to stop Cura from doing this? One way that worked was to place support blocker at this region and set the bottom layer and top layer for that to 0. This is however not a very clean fix.

 

I would love to hear how this can be fixed.

[SwayYayYay 0]

any update to this/? I'm having the same issue. I noticed that Skin expand/removal tends to help with it but I am still getting it . even if I increase the walls to say 4 or increase the infill it won't go away. the only way I can get it to go away is if I completely disable top/bottoom layers wich I CANNOT do nor do I want to change my infill type (grid)

[gr5 2,176]

Please post screenshot and more importantly post your project file.  In cura do menu "file" "save project" and post that file here.

 

Usually this happens when there is a problem with the model.  The STL files are a list of unordered triangles with a "normal" and the normals are often backwards - they say which side of every triangle is inside (or is plastic) and which side of every triangle is air.

 

There are tools to fix this.  There are 3d modeling programs (not what I would call CAD) that often reverse the normals and the two worst offenders are blender and sketchup.  But there are great tools within those programs and lots of articles, videos, techniques to avoid these.

 

Also if a triangle is missing in the mesh, cura can get confused there also and skin all the way across an opening.

[SwayYayYay 0]

I have gotten some help, they advised to tinker with "skin removal width" , but I find that increasing this also affects my bottom layer .  I have linked the Cura File , I believe the issue comes from the steep angles but my goal is to remove those "Extra Skin" without compromising the infill or the bottom layers, its ok if the model has some gaps in it

CCR10_test.3mf

[gr5 2,176]

I loaded and sliced your project file.  It sliced fine for me.  I have cura 5.4 so maybe it's something in a newer version?  But I don't think so - I think it looks the same as in your screenshot?  I just saw top and bottom skin.  And walls.  The way you described it I expected to see a solid layer occasionally - like an internal shelf inside the part.  Do you get that?  I did not see that.  What version of cura do you have?

[Slashee_the_Cow 269]

6 minutes ago, gr5 said:

What version of cura do you have?

They're running 5.6.

 

There aren't (as far as I can see, anyway) any individual layers where skin and infill overlap, but together, yes, there is a bit of overlap:

 

If you reset Top/Bottom > Skin Removal Width to its default, the effect is significantly lessened:

 

If you also reset Top/Bottom > Skin Expansion Width to its default, then the problem basically disappears (which is what the expansion width is for, to remove small holes):

 

With those reset, it looks fine to me:

[gr5 2,176]

Oh!  Try Cura 5.4.  There is absolutely no yellow at all when I use your project file.  I think there are some bugs in versions of Cura newer than 5.4 which is one of the main reasons I'm still at 5.4.  This is only one of the minor bugs we've been seeing.

[SwayYayYay 0]

4 hours ago, gr5 said:

Oh!  Try Cura 5.4.  There is absolutely no yellow at all when I use your project file.  I think there are some bugs in versions of Cura newer than 5.4 which is one of the main reasons I'm still at 5.4.  This is only one of the minor bugs we've been seeing.

yes that is because I had altered these settings around. however their is 2 issues . the first more important, adjusting these settings also impacts the bottom layer, making an incomplete bottom layer as shown in the Screenshot. the second issue is that even with these settings at the last 100 layers in the preview that "Extra Skin" is still being added 

 

 

[SwayYayYay 0]

4 hours ago, Slashee_the_Cow said:

They're running 5.6.

 

There aren't (as far as I can see, anyway) any individual layers where skin and infill overlap, but together, yes, there is a bit of overlap:

 

If you reset Top/Bottom > Skin Removal Width to its default, the effect is significantly lessened:

 

If you also reset Top/Bottom > Skin Expansion Width to its default, then the problem basically disappears (which is what the expansion width is for, to remove small holes):

 

With those reset, it looks fine to me:

my goal is to completely remove the "Extra Skin" its a really specific use case. I want the model to only have walls and infill inside no "Extra Skin". I would be ok with increasing the walls or possible air gaps. 

[Slashee_the_Cow 269]

37 minutes ago, SwayYayYay said:

my goal is to completely remove the "Extra Skin" its a really specific use case. I want the model to only have walls and infill inside no "Extra Skin". I would be ok with increasing the walls or possible air gaps. 

Well why didn't you say so?

1. Set Top/Bottom > Skin Expand Distance to 0. This has to come first because the option will disappear in just a moment.
2. Set Top/Bottom > Top Layers to 0.
3. Set Top/Bottom > Bottom Layers to 0. (Expand option disappears here)
4. Set Top/Bottom > Initial Bottom Layers to 4 (or whatever you want).

Now you still get a full footprint:

But absolutely no pesky yellow top/bottom inside!

[GregValiant 1,256]

The "skin" is added because of the part geometry.  It's an angled area and the slices are always parallel to the build surface.  That's why getting rid of the "skin" requires fooling Cura.  It's a trigonometry problem and that makes it Pythagoras' fault.

 

I know this is hard to see but on the left is a "revolved" shape with 2.4mm thick walls.  On the right is the profile that was revolved.  The Wall Count is 3 which will be 1.2mm at a 0.4 line width.  The magenta lines represent slices through the model.

 

 

A slice through the vertical wall shows that 6 extrusions will exactly build the 2.4mm wall.

 

A slice through the upper angled area shows that "3 walls" only provides a "thickness" normal to the exterior surface of 0.31mm and so Cura adds "skin" to build the wall thickness to the 1.2 that the settings asked for.  Since the slice through the wall at that magenta line is 9.27mm wide, and since and the total of 6 wall extrusions only accounts for 2.4mm of that, then the inside 6.87mm will be skin.

Different geometries will give slightly different effects but Cura will always build a wall to the thickness that has been asked for in the settings and that thickness dimension will be "normal" (perpendicular) to the exterior surface.  If you want it to be different then other settings need to be adjusted as Slashee advises.  You need to explain to Cura that "Yes, I want 1.2mm worth of walls over there, but over here a thinner wall is OK."

 

Different geometry.  The orange lines indicate a 1.2mm thick wall normal to each surface.

The 3.44 dimension will be skin so that the angled area also has a 1.2mm wall.

[Slashee_the_Cow 269]

Thank you @GregValiant for that thorough and convincing explanation of why I should have finished high school maths.

[GregValiant 1,256]

For some of this stuff I have to get out my slip-stick.