How to creat 'solid' STEP file whithout 'model tree' (i.e. Single piece) in Creo?

Hello all,

I am struggling to create Single piece Solid STEP file in Creo. I have used "Merge" option, but it is very much time consuming. I need to convert hundreds of such assemblies in STEP file.

I could succeed to create Single piece Step file with Surface option, however it is difficult to apply density and calculate the CG and MOI calculations.

Please assist.

Thank you in advance.

Shriram