Hello,
I am preparing a model for a 3D print and would like some advice about merging shapes. I need each block of shapes to be a single shape so that the printing software reads it correctly.
I have the individual shapes grouped but how do I merge them into a single form, removing interior walls
1.skp (350.4 KB)
All of the ones I selected in your model were solids. That message is telling you that something you selected isn’t a solid group or component. Figure out what isn’t solid and fix it or remove it from the selection set before running Outer Shell.
If you were trying to run Outer Shell on what I show selected, it won’t work because it’s all loose geometry. To get that to make a solid group you would need to do something different like erase internal faces.
I was working with the ones you had individually grouped because that’s what you said you were working with.
There is more in your model, and the other things aren’t made up of solids. Only this one is solids.
Edit: @DaveR wrote the same thing while I was typing
Ahh okay yes I see now, solved it perfectly.
Thank you so much for the help
A note on forum usage and conventions: typically, the post that is the best choice to marke as the Solution is the post that provided the initial answer (in this case, @DaveR’s first reply), rather than your own reply that summaries the final result. 
