Bottom-up assembly modeling is a part-centric modeling method where the assembly design is started with a principal structural or functional element, and individual parts are designed in relative isolation from the overall assembly.
When you use a top-down design approach, you create space claims called envelopes for components in an assembly. You build the detailed parts and subassemblies to fit the envelopes. … When you use a bottom-up approach, you start with a complex assembly and simplify it.
Bottom-up is the most traditional method used by CAD operators. Parts are modeled and them are inserted into the assembly using mates to position and fix them in relation to other components. Any changes to a part will need to be done by editing it individually.
Top down approach starts with the big picture. It breaks down from there into smaller segments. A bottom-up approach is the piecing together of systems to give rise to more complex systems, thus making the original systems sub-systems of the emergent system.
What is assembly workbench?
The assembly workbenches use constraints and expressions to create relationships between the objects in your model, in order to mathematically tie the objects in place, for example, “this face should stick to this other face”, “this cylinder should be concentric to that circle”, “this point should follow this edge”, …
What is Assembly CAD?
An assembly is an AutoCAD Civil 3D drawing object (AECCAssembly) that manages a collection of subassembly objects. Together, assemblies and subassemblies function as the basic building blocks of a roadway or other alignment-based design.