How to model a box that contains two boxes of different material?

[Anonymous]

Hi

I'm trying to make a *supposedly* simple model as follows: It's a large box, that contains (envelopes) two smaller boxes. The two small boxes are one material, and the big box is a different material. I'm making this for importing to SimScale for a thermal analysis.

I'm new to Fusion360 and I'm sure this would be trivial, if I knew what I was doing... What I tried so far was to make the two boxes. Then I start making the big box, but as soon as extrude the big box over (enveloping) the small boxes, the small boxes disappear from view. The big box doesn't show either. In the browser on the left, I only see the two small box objects.

What am I doing wrong?

[davebYYPCU]

Too many things to guess, 

File > Export your file, and add to another message with the Attachments paperclip icon, found under this window.

[jeff_strater]

I suspect that what you are seeing is the big box's "Operation", by default, will be set to "Cut":

So the big box will cut away all the material from the smaller boxes.  If you instead change the Operation to "New Body", it will create a new body, which envelopes the smaller ones:

However, this will create a solid box with material which overlaps the smaller boxes.  You can see that if you set the opacity of the large box to something less than 100%:

If that is what you are after, then you're done.  Just understand that the big box has material in the same space as the smaller boxes.  You can use Combine to subtract that material if you want.

[WyzeOwl]

This looks like it would be better to model each box as a separate component. Doing this gives you the flexibility to edit any of the 3 without changing size, positions, orientations or properties of the other components. An excelent Quick Tip on Bodies v Components can be found here https://www.autodesk.com/products/fusion-360/blog/quick-tip-body-v-component/ 

In the screen shot there is a main assembly containing 3 objects; 1 box and 2 cubes where, as shown, materials are assigned by right clicking on 1 of the components and selecting Physical Material. Assigning a material is done by selecting and dragging from the list to the component.

If, on the other hand you are trying to create 2 solids within a larger solid, the same "create component" is used however each of the smaller boxes would need to be modeled within defined cavities inside the larger one. 

[TheCADWhisperer]

Has your instructor given you an assignment sheet that outlines the assignment?

[Anonymous]

Jeff,

That looks pretty much like what I want to do. 👍 I followed your steps, but I couldn't extrude the big box over the small one. The default operation was actually "New body", but as soon as the extrusion touched the small box, it changed to "Cut". I wasn't able to change this. So, I made the boxes apart from each other, and moved the small box into the big one. By the way, it seems we're using different SW versions. I can't find the "Box" menu anywhere, but my "Extrude" menu seems to do the same thing.

I set the opacity lower to see the small box, no problem. But I'm not able to use the "Combine" command to let the small box cut out the material from the big one. None of the operations work, bodies disappear, both visually and from the browser. How should I do this?

[jeff_strater · Accepted solution]

Yes, what you describe is expected.  Fusion will try to auto-choose the operation type for you.  Any time that your tool body touches another body, Fusion assumes you want to cut (which is a reasonable assumption, I think).  But, once Fusion has flipped the type to Cut, you can go back into the dialog and change it again.  And, you are right, the logic for Extrude and Box are identical (they are the same underlying command).

Here is a screencast that should help illustrate how to do this:

[Anonymous]

OK, done!

Thanks so much for that screencast Jeff; it explained everything I needed to know. Very useful also to see the toggling of visibility and section analysis.