About Replacing Assembly Components
When one assembly component is replaced by another, the new component is placed in the same geometric location and in the Model Tree. If the replacement model has the same constraints and references as the original model, placement is done automatically. If references are missing, the Component Placement tab opens, and you must define placement constraints. Any assembled component can be replaced, including a member of a group or a UDF.
More than one component at a time can be replaced in an assembly. Multiple occurrences of a single component can be replaced by a single component, or multiple components can be replaced by multiple unique components.
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Replacing and substituting components are two different actions. Substitution exchanges one component in a simplified representation for another and is performed in the context of a simplified representation.
When you replace a component in an assembly a dependency is created from the assembly to the outgoing component. The dependency created is used to restore all references when you replace the outgoing component back into the assembly. Clear the Remember These Components check box to remove the dependency for an unrelated or interchange component.
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You can remove the dependency to an interchange assembly in the Reference Viewer dialog box. Click Reference Viewer or select the component in the Model Tree and choose Information > Reference Viewer and select the interchange reference in the Parent/Child Graph. Right-click and choose Break Dependencies.
Replacing Components Automatically
Automatic replacement of components can be performed only if the replaced model is one of the following types:
A Shrinkwrap feature
An Inheritance feature
A module or a module variant
A Merge feature
A member of a Family Table
A functional interchange assembly
A model that is declared to a notebook 
Positioning a Replaced Component Manually 
When you replace a component with one that is unrelated by Family Table, interchange assembly, or notebook, you must manually reposition the replacement component and any components that were assembled to the original part. The system always tries to assemble the component automatically. If it cannot, it keeps as many constraints as possible.
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When you replace a flexible component with an unrelated component the varied items become locked and the replacement component is not flexible.
Use the Unrelated Component option to manually replace the model with a selected component. While similar to deleting and assembling a new component, with this method you can automatically place the newly replaced component in the same regeneration position.
Automatically Selecting Components to Replace
You can choose the replacing component without selecting the components to replace in the assembly. When you select a replacing component and click Select All Automatic, all components that can automatically replace the selected component are listed in the Select Current Component(s) box. A Replace column appears in the Model Tree. The name of the replacing component appears next to all components that can be replaced automatically. OK Manual appears for components that can be selected manually. When you select a component manually in the Model Tree, it is added to the list of selected components and is replaced as well.