Unfolds faces of an ACIS object. This is also knows as obtaining the involute of a surface.
Example 1

For a simple example, start with a truncated cone, using the Cut Cone by Plane option.
Activate Unfold Face. Click when the curved face is highlighted. (Only faces that can be unfolded will be highlighted.)
A preview of the unfolded face will appear.
To create the face, select Finish from the Inspector Bar or local menu.

Example 2
For a more complex example, start with a Rectangle, filleted using the Fillet tool.
Create a cone from this polyline, using the Specify 2D Base option.
Create some cylinders and use 3D Subtract to remove them from the cone.
Activate Unfold Face and click the cone.
Select Finish. If you move or delete the cone, you can see the unfolded face clearly

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