There are two basic ways of creating any assembly model.
• Top-Down Approach
• Bottom-Up Approach
The assembly part file is created first and components are created in that file. Then individual parts are modeled. This type of modeling is useful in a new design.
The component parts are created first in the traditional way and then added to the assembly part file. This technique is particularly useful, when part files already exist from the previous designs,and can be reused.
Mixing and Matching
You can combine these two approaches, when necessary, to add flexibility to your assembly design needs.