Making a six-part mould- Cutting by planes

Question

I'm new to blender and hope someone can help. I want to make a six-part-Mould. Therefore I created three planes exactly shaped as I need them to be. Now I have problems creating the Mould-parts using boolean modifiers. Please see the images attached. Am I on the right path or is there a much better way to cut the cube into pieces then by adding the right selection of boolean modifiers?

My goal is to first cut the cube into six pieces, the filling of the cut surface has to be in the exact shape of the plane. Next step would be to cut out the object out of each cube. What I have then should look similar to image 1, on every cube.

What I tried exactly: unsuccessful one (image 3)

• Boolean - Intersect with axial Plane (B-Mesh)
• Boolean - Intersect with second plane (Carve)
• Boolean - Difference with object I want to cut out (B-Mesh)

Successful one (image 4)

• Boolean - Difference with object I want to cut out (B-Mesh)
• Boolean - Difference with axial Plane (Carve)
• Boolean - Difference with third plane (carve)

So I do not really understand what happens, why one works and the other fails.

I would be very happy if someone responds to my problem. I could also upload the blender-file. (is there a way to upload it in this forum?) Thank you in advance!

Image 1: Two-Part Mould I made yesterday (to give you a better understanding about my goal)

Image 2: The cube with the three planes

Image 3: Unsuccessful part

Image 4: Successful part

Answer 1

The question is simple but the answer is a bit complex.

How does boolean modifier work

The boolean modifier can do 3 boolean operations between 2 solid objects. They are simple and fully described here. The point I want to focus to is that they both need to be solid. They cannot be a cube and a plane, because the operations (union, difference and intersection) operate on volumes, not on faces/edges/vertices.

In my example the situation is simple, because I'm going to use only one plane. To do it in your case you will need to repeat this instructions recursively for every cut.

Extruding planes to give them a volume and using the Boolean modifier

This image shows a cube and a plane.

I want to use the plane as a "blade" to cut the cube in two parts. So I select the plane and go to edit-mode:

I extrude it to have a volume that completely covers one of the two parts of the cube:

I go back to object-mode, hide (presing H) the extruded plane, I select the cube and add a boolean modifier to it. In the modifier settings i choose the extruded plane as the "Object" I want to use to do the boolean.

As "Operation" I can choose "Difference" to obtain one of the two parts:

...or the "Intersection" to obtain the other part:

To have them both I need to duplicate the cube and apply the "Difference" boolean modifier to the first and the "Intersection" to the other.

You'll need to do this steps with the first part to divide the first object in two, and then to repeat them recursively on the pieces you obtained to divide them again, until you have all the pieces.

I know it's a struggle, but I don't know other ways to do this.