How can I save an assembly as a part to use the combine tool? (create a negative shap

[yagotuneli]

Hello



I'm Yago and I'm from Brazil.



I need to print a 3D part and this part need to be a negative form of an assembly (M600 PRO Drone image attached). I'm tried to do this using the combine tool from Solidworks 2017.

My question is how can I save an assembly as a part to use the combine tool? The part needs to appear like a solid body and I can't get this result.



I've tried possibilities like:

-Save the assembly as a part;

-Defeature tool;

-Convert to bodies.



The problem is that the final part is not a solid body and the combine tool can't be used or some parts appears like surface and the tool doesn't work.



Could somebody help me out with problem? I can send the files to who needs after because they exceed the maximum size allowed here.

There are two pictures attached to show how I need the negative form.



Thanks a lot.