Rigid and Flexible Assemblies

When creating parts in your design you will most likely create assemblies as well.  An assembly is a group of parts held together by mates.  Consider the assembly mechanism below.  The mates are created such that the top handle is able to rotate, thus transmitting the motion from one yoke to another. 

We may create subassemblies by placing one premade assembly into another.  In this case we are placing the universal joint mechanism as shown above into a new assembly

Once the universal joint mechanism assembly is placed into a new assembly, you will find that the entire mechanism is rigid and unable to move despite having no restriction for movement.

By default, when an assembly is placed into another assembly it is treated as rigid.  To change this we can right click the subassembly and select Properties

When the component properties box opens navigate to the Solve as section and select Flexible.  Accept.

With that change implemented you will find that the subassembly mechanism is now freely available to rotate.