Creating a hole in a mesh for 3D printing

[setiawanJ3NT5]

Hey guys, I'm trying to add a square hole into a mesh.

I imported an STL file, and made several plane cuts so that I was able to delete a square on the top of it, and then merged all the cut pieces of the mesh back together (the purple/pink portion of the model). I then created a solid rectangle inside the hole, and deleted the top face, so that I now effectively have a square hole (the yellowish part of the model).

However, no matter what I do, when I try to save it as an STL and open it in Cura, the square hole is gone, and I get flat surface on the top instead. Any ideas on how to get this to come out 'properly' in Cura? I've tried to "BRep to Mesh" the square hole, merge it with the purple part, but it still the top becomes flat in Cura. Similarly, if I merge them together and then "Make Closed Mesh" in Fusion 360, the top also becomes flat.

Any tips or suggestions would be much appreciated. Thanks!

[LeonardoBN]

Hi @setiawanJ3NT5. Did you checked the mesh for errors before/after that manipulations (e.g., Netfabb, 3D builder and MM)?

Have you tried using Meshmixer for these operations?

[setiawanJ3NT5]

Sorry, I'm kind of new to this. How would I go about checking for errors? When I import it into Cura, Cura says that it's not watertight - does this help at all?

I just installed Meshmixer, but not entirely sure how I would go about using it to make this kind of hole.

[LeonardoBN]

Is it not watertight!? It is an important information.

This meann your file has errors. If your mesh is not watertight (you will hear manifold too) it doesn't has a closed surface, so you can have trouble slicing it. Sometimes the slicer can fix small errors, but I prefer to check it externally. I like to use Meshmixer and Netfabb for this.

Meshmixer can be tough at first, but it is a very powerful tool for mesh manipulation, like the one you want to do.

To give you a direction, look for Plane Cut, Inspector (to check errors), Boolean Difference (to subtract volume) and Meshmix (to create the box you will subtract). 

If you have trouble in any operation, you can post your questions on the Meshmixer forum:

https://forums.autodesk.com/t5/meshmixer/bd-p/6013 

Of course you can do this using Fusion like you did, but you can face some problems. 

As you already have this not manifold file, try uploading it here:

https://service.netfabb.com/service.php

After checking your file, try slicing it on Cura again.