About Creating an Assembly
To create a subassembly or an assembly, you must first create datum features or a base component. You can then create or assemble additional components to the existing component(s) and datum features.
Assembling Components
You can add components to an assembly in the following ways:
Assemble a component parametrically by specifying its position relative to the base component or other components and/or datum features in the assembly.
Assemble components manually or automatically using predefined component interfaces. Refer to About Automatic Placement of Components for more information.
Assemble a component nonparametrically using the Package command in the Assembly group. Use packaging as a temporary means to include the component in the assembly; then finalize its location with assembly instructions.
Create a part or subassembly directly in Assembly.
You can use notebooks and specify declarations to assemble components automatically. You create these assemblies by automatically aligning datum planes and axes of different parts in accordance with the declarations previously made in Notebookt and Part modes. You can specify declarations, and after a component has a declaration, it can be automatically assembled.
You can include a component as a member of an assembly without actually placing it in the assembly window. This technique allows you to list the component as a member of the assembly even if the component is not ready to be assembled (for example, it does not have geometry). The system lists included components in the Model Tree and BOM, but does not display them on the screen or include them in mass property calculations. To add constraints later, you can redefine the placement of the component.
You can remove a component from an assembly by deleting it or replacing it with another component. In addition, you can also redefine the placement constraints for assembled components.
To place a base component or feature, you must either create three orthogonal datum planes as the first feature, assemble an existing component (part, subassembly, or skeleton model), or create a base component.
A component that is added into an assembly is saved in the assembly directory.
Using Datum Planes as the First Feature
When you create three orthogonal datum planes as the first feature in an assembly, you can assemble a component with respect to these planes, or create a part in Assembly as the first component. Using datum planes as the first feature has the following advantages:
You can redefine the placement constraints of the first assembled component.
You can pattern the first component you add, creating a flexible design.
You can reorder subsequent components to come before the first one (if the components are not children of the first component).
Assembling a Component Parametrically
Using the Component Placement tab, you can assemble components parametrically by establishing constraints that define the component's position in the assembly. The component's position changes according to changes in components or assembly features to which it is constrained.
Creating a Base Component
If you do not create three orthogonal datum planes, the base component is the first part, subassembly, or skeleton model placed into an assembly. In many ways it is like the base feature of a part. The initial assembly units are the same as the units of the base component. When a base component is the first object in an assembly (before any assembly features), no placement constraints are defined. You place the component with the Default constraint. If you replace a base component with interchangeable components, the replacing components will always be placed by default as well.
When you create the first component of an assembly, you can either create an empty component or copy from an existing component. As with an assembled base component, the initial assembly units are the same as the base component, and interchange components that replace the created base component will always be in the default orientation.