Cura 5.2; Inner walls dissapear in single models

[printnewb 2]

I have a piece of a magnet holder. It needs to be stiff so that is why I need internal walls.

 

I have asked about something similar in the past but this time I have a better model that is closed.

In the image above the upper model is actually 3 separate models merged together to have them in the same location as they were during STL generation.

Now the internal walls are overlapping but that is of no concern due to the "union overlapping" feature.

When slicing the inner walls get sliced as well just as I'd like.

Below it we have the same model yet exported as a single STL. Now the internal walls are no longer being sliced even though they show up in the x ray view quite good.

 

Is there a setting I am overlooking that will get the internal walls sliced on single STL models? If it is not possible it would mean a tremendous amount of extra work splitting up larger models into many smaller pieces.

 

Please see the 3fm file for reference.

CE5P_magnet holder disk single inner wall issues.3mf

[GregValiant 985]

Something like this?

There are 3 Support Blockers set to Modify Setting for Overlaps and as Infill Mesh.

[printnewb 2]

Interesting, how does this working with erasers work? From the screen shot I am not sure I understand.

[GregValiant 985]

Support blockers have options.  The button above the Support Blocker button gives you the options of Print as Normal Model, Print as Support, Modify Settings for Overlaps, and Support Blocker.

When Modifying Settings for Overlaps the block can be configured either as a Cutting Mesh or as an Infill Mesh and each has different effects on the main model.  The blocks can be scaled and moved like any other mesh.  It takes some playing with and not all settings are available but you can make alterations to the model that rests within the Modifier Mesh block.

In the project file there are two rectangular blocks and a cylindrical block (this from a plugin that is loaded from the MarketPlace).  Select each and you will be able to see how they are set up.

 

 

GV_magnet holder.3mf

[printnewb 2]

Thank you Greg for the 3mf file.

 

On my end though I can see 2 remaining issues that would hinder using this technique.

 

1) The wall in the middle between the inner and the outer part is 2 lines thick, even when setting the wall count to 1 of the eraser used there.
2) The walls connecting the magnet hole do not appear on layers before layer 6

 

 

would it be an idea to change this topic to a feature request? To also be able to slice internal walls?

[GregValiant 985]

When Cura is given a model to slice it is always best if it is the model you want.  When you give it a model that is "Almost what I want except for this part over here..." and try to adjust the design in Cura then things get tricky.  Cura is not a CAD program.  You can make some changes that will alter the way a model is sliced, but you really can't make a new model.

In the 3mf file I put together, the modifier blocks are 2mm thick and so Cura will print them 2mm thick.  The "Line Count" doesn't come into it.  If you change the blocks to be 1mm thick then they will be a single line width.

The long block is not resting on the build plate (my bad) and so it doesn't start to modify the model until layer 6.

Changing the two blocks to 1mm thick and dropping the long block to the build plate you get this on layer 2:

 

The only reason I added the cylindrical block was to show another possibility.  I use them at screw connections because thin walled screw holes often deform from the compression of the screws and nuts and then the screws self-loosen.  PLA in particular is susceptible to cold-flow deformation.

 

As far as a feature request goes, you can of course make the request over on Github.  I've seen many requests to add functions that will alter a model in Cura.  You need to remember though - Cura is a slicer, not a CAD program.

This shot is with a model I created on the top right, and your model on the lower left.

In your model, you are trying to alter a solid block and put partitions in.  My model was designed with a 1mm shell and 1mm interior partitions were designed in.  The slice settings have "Support Infill" with no walls, no interface, top/bottom distance = 0 and XY distance = 0.  You can see that my model is full of support rather than infill.  The reason is that my model is hollow.

[printnewb 2]

thanks for the heads up regarding the screws that can come loose. never thought about that yet

[printnewb 2]

one thing we have not really talked about is;

 

Is having the ability to slice internal walls a feature that is useful or not?

 

You all know my stance on this by now. What is yours?

[GregValiant 985]

Consider any solid model like the one you have there.  Other than the three holes it's solid through and through.  How do you put partitions into a solid object?  There isn't room for them because there is no free volume within the cube to put your "inner walls".

We went over using the support blockers to modify the slice, but it's not the same as having a model that is exactly what you want.  You can only fool the software so much and after that it's back to the drawing board.

Part of the design constraints of any part will be how it will be fabricated.  Can it be a single piece or should it be multiple pieces that get fastened together?  Should we build a mold, or can we get by with FDM?  

When you decide that the part will be built using FDM then that places certain restrictions on the design.  It also allows for certain design freedoms.  If you were going to build an injection mold for the part then it would have different restrictions (and different freedoms) that would have an effect on the design.  (On the top of the pile is production requirements.  If I need 60,000 pieces/month then FDM goes right out the window.)

I vote to let the slicers be as good as they can at slicing and the CAD software be as good as it can at allowing me to come up with the parts I need/want.  I design any part while keeping in mind the constraints of the fabrication process.  If it can be done with a 3D Printer then I give the slicer the part I want and not just a part that "is close except for....".

 

Here I've spun the one model around so it's square to the build plate.  I changed some of the infill settings.  To me this looks like you get the inside partitions for free.  I don't know the design intent though.

[printnewb 2]

insightful and in-depth, thank you