Design in Context

Design in Context

Overview: There are many advantages to top-down modeling, the greatest being the ability to design or edit in the context of the assembly structure. It is important to understand the following concepts when using design-in-context principles:
- Define the new component before creating any parametric geometry when possible.
- Sketching in the context of an assembly.
- Switching back and forth between top-down and bottom-up methods.
- Creating subassembly files.

Switching Between Top-Down and Bottom-Up

You can use a combination of top-down and bottom-up methods in defining the assembly structure. You can also use a combination of these methods in designing and editing individual component geometry. For example, in an existing assembly, you create a new component and a "black box" shape to define its location and overall size within the assembly structure. You can save this part, close the assembly, and design the detail of the component part using bottom-up methods. The combination of methods provides the best of both worlds: top-down for positioning and evaluating size restrictions and bottom-up for detailing the component without having to work with the entire assembly.

Creating Subassembly Files

Remember, components are the piece parts making-up an assembly. These piece parts can be used in multiple assemblies and multiple subassemblies. Therefore, it is always a good idea for each unique piece part to have its own part file. Even these piece parts can have their own component piece parts. For example, a coupling may be a piece part in a large machine assembly but the coupling also has its own components (plates, shafts, and hardware). The coupling is an assembly itself and a subassembly in a larger assembly. The piece parts in the coupling assembly should not be added directly to the machine assembly as components. Instead, create an empty file to act as the coupling assembly file, such as coupling-assy, and add all of the related coupling components to this file. Now coupling-assy can be added to a larger assembly as a subassembly. When you add a subassembly to an existing assembly, all of the components are added as well. In terms of design-in-context concepts, use the Insert | New Product to create subassembly files before adding or designing new components. Doing it this way creates a subassembly structure that is much easier to manage and manipulate than if you simply add the components to the top level assembly. Be careful of using the Insert | New Component to create a subassembly. If you do this, the subassembly only exists within that individual Product file and cannot be accessed by other CATIA Product files.