Design Modeller not uniting bodies, having trouble with boolean function.
 

Hey guys, I am currently trying to run CFD analysis using ANSYS19.1 on a semi-trailer assembly I had created using creo. Before uploading it onto DM I had combined all parts of the semi-trailer into one new part and then had saved that part as a STEP file.

That step file when opened up on in design modeller still had a several bodies associated to it, I had just created a new part in the DM to combat that. Leaving me with 1 part and 10 bodies.

I was having trouble adding in an enclosure to the body and through a quick search figured there might be errors I need to rectify. After running several repairs on the body I was able to add in the enclosure finally.

Then when I tried to add in a boolean function subtract, it wouldn't let me giving me the error "Error: Operation would result in non-manifold bodies
Context: Geometry Engine, while generating Feature Boolean1".

After that I had tried to unite using boolean function but I am unsure if that did anything as the part still had 10 bodies. I had even tried using 10 different boolean functions in order to subtract it one at a time. The problem comes in when the most complex geometry is being subtracted.

If anyone can assist that would be great, this is my first thread and I'm quite new to CFD. Thanks.