Using FDM technology to build complete assemblies gives designers greater design
freedom and eliminates the time required to assemble separate parts. (Figure 1)
The use of FDM technology enables:
• Internal moving parts
• Functional mechanisms
When designing an assembly with FDM technology, proper clearance between mating
and rotating parts is required to allow for an accurate fit and function. The design of the part and build orientation both play an important role.
1.1. Orienting Parts for Assemblies
Before making design alterations it is important to have a strategy for the build
orientation. Orientation of the mating components can affect the fit of the
assembly and will determine the necessary clearances.
Answered with a tutorial: https://grabcad.com/tutorials/how-to-build-complete-process-assemblies