Difference to union for 3D printing purpose

Support Modeling
1

Hello everyone,

I’m new to blender. I would like to know if there is a quick way to have a boolean difference to union.
Let’s say I have a basic setup with a solidify cylinder and a cube.
My aim is to keep only one part of the cube going out from the cylinder.

Then I apply a boolean difference on the cube, selecting the cylinder as the cutting shape.

I then apply the modifier and delete the part I don’t want by selecting with L in edit mode.

Then I apply a union modifier to “merge” the cube and the cylinder. It works, but as geometry don’t overlap the result is not what I’m expected, I have that :

image
image1920×1040 223 KB

To test it, I’m using the 3d printing add-on and click on “Make Manifold”, and everything goes wrong.

Any help would be appreciated,

Thanks in advance,

Pierre.

2

Can you try and be a little clearer, especially with the screenshot. Why do you need to do both difference and Union?

3

Sans titre
Sans titre1920×1040 175 KB

Hello,

Sorry if I’m not clear, my aim is to keep only the red part of the cube and the cylinder as a manifold mesh.

Thanks,