Unwanted top layer - or: how to use horizontal layers inside model without a final top layer

[Cumulus7 0]

Hi,

 

i have a big problem printing some STLs. The STLs are open on bottom and top. However, when i enable the top/bottom layers in cura, cura closes the bottoms and tops.

If i disable bottom/top layers by setting them to 0, cura also does not print some horizontal parts inside the model that should be there.

 

This is my test-part: https://www.thingiverse.com/thing:2115282/#files

Cura 3.1 is used.

 

I made some screenshots:

1: In solid view you can see the horizontal part in the blue circle.

2: with top-layers enabled, the model is closed on top (but should be open)

3: inside the model now looks good

4: without top layers the part is missing

 

So it seems that either i can

a) have the model open but parts missing

b) have the model closed but inside its OK

:-(

 

I already tried the "cut mesh" tricks: the mesh-part where i have to enable the top-layers always inserts an artificially inserted closed top/bottom layer at its boundaries -> no help there.....

 

Any help is greatly appreciated!

 

Greetings,

Markus

Edited January 27, 2018 by Cumulus7

[burtoogle 513]

I just tried slicing that using craftware (not that I normally use it for anything other than viewing gcode) and it also filled the part with infill and put a top on it. So maybe the model is just broken in some way?

[burtoogle 513]

Yes, that model is definitely weird. S3D also slices it with infill and look at the model before slicing, the rear wall is always missing no matter which way the model is turned.

 

 

[gr5 2,172]

Those walls appear to be infinitely thin.  You need to make them thicker - I recommend 0.5mm minimum  1mm even better.  At 0.5mm walls this thing will be pretty delicate.  At infinitely thin walls, well, there's nothing to print.

[kmanstudios 1,120]

None of the walls are manifold. They are all 2D sheets and therefore not able to slice.

Making the walls 0.8mm with an inside shell (so as not to expand the outer surface) it slices quite well.

 

Running it through 3DS MA's STL Check I round the errors that confirmed the 2D aspect of the model.

General number of errors:

 

When getting into specifics, you can see it is all open edges.

Specific errors:

 

Here is the file that I sliced:

Ste_fuselage_5_08mmWalls.stl

[gr5 2,172]

How did you "make them all 0.8mm thick"?  Is there a free program that this guy can use to do that?

[kmanstudios 1,120]

I used 3DS MAX. I am not sure what is available for free.

 

Kinda sucks that these people making these models are not making them correctly for the most part.

 

The 0.8mm thick was based on your previous suggestions in other threads of making the walls twice the diameter of the nozzle.

[kmanstudios 1,120]

I just found this tutorial on how to do it in Blender.

Edited January 27, 2018 by kmanstudios

[Cumulus7 0]

THX everybody,

 

so there is no setting to tell Cura to:

a) print horizontal geometry

and

b) not "invent" or "add" additional geometry?

 

All the detail is essentially there....

The shell has no "depth" since it should be printable with a single layer. That seems only possible without a given depth, since no fixed nozzle-size is required.

 

I might try the blender way though....

 

For now i help myself with some "cut meshes" that enable the top/bottom layers at some key-points.

Not perfect, since those cut-meshes generate a top/bottom-layer themselfes, but that layer is not as extensive as a top/bottom layer over the whole wing.

(other cut-meshes enable a second wall at the start and end of each wing-part)

 

That kinda works for the wings. I haven't looked at the fuselage yet. 

(i build the EasyMaxx glider https://3dlabprint.com/shop/easymax-001/)

 

Greetings,

Markus

 

Edited January 27, 2018 by Cumulus7

[kmanstudios 1,120]

On 1/27/2018 at 2:18 PM, Cumulus7 said:

THX everybody,

 

so there is no setting to tell Cura to:

a) print horizontal geometry

and

b) not "invent" or "add" additional geometry?

 

All the detail is essentially there....

The shell has no "depth" since it should be printable with a single layer. That seems only possible without a given depth, since no fixed nozzle-size is required.

Slicers are designed to slice the models as made, not really compensate for bad modeling. Also, at what point are users asking a slicer to not be a slicer and become a faux modeling program?

 

The 2D sheet cannot be sliced because it falls below the sampling range of capability. You may see it, but it has no depth and therefore, not 3D. 2D sheets like what you are trying to work with are just flatland......

 

You may also want to look into the Nyquist Frequency which governs all sampling operations.

[edwardlego 0]

is there any way to do what the original post asked for? removing the top/bottom layers but keeping other horizontal faces closed?

my model is very wide at the bottom, but has overhangs which are left open when i set bottom thickness to 0

[kmanstudios 1,120]

The Op's files had to be fixed.

[gr5 2,172]

3 hours ago, edwardlego said:

is there any way to do what the original post asked for? removing the top/bottom layers but keeping other horizontal faces closed?

my model is very wide at the bottom, but has overhangs which are left open when i set bottom thickness to 0

A photo would help.  I'm wondering if you are asking for something completely different than kman and I are thinking you are asking about.

 

Well let me ask you this - when you say "removing top/bottom" do you mean in CAD?  Because if so I think the answer is no.  But if you want to remove them in cura (but they exist in cad) then I think the answer is yes.

 

If you just put up an infinitely thin wall in cad cura will slice this wall PERFECTLY.  To within a billionth of an inch accuracy.  It will print nothing which is what an infinitely thin wall is: nothing.

[edwardlego 0]

4 hours ago, gr5 said:

A photo would help.  I'm wondering if you are asking for something completely different than kman and I are thinking you are asking about.

 

Well let me ask you this - when you say "removing top/bottom" do you mean in CAD?  Because if so I think the answer is no.  But if you want to remove them in cura (but they exist in cad) then I think the answer is yes.

 

If you just put up an infinitely thin wall in cad cura will slice this wall PERFECTLY.  To within a billionth of an inch accuracy.  It will print nothing which is what an infinitely thin wall is: nothing.

it's about settings in cura. i just want to avoid printing the solid bottom layers, saving hours in some prints, but keep the overhanging bottom layers that aren't touching the buildplate