Flattening Sheet Metal Bends
You can flatten the bends in a sheet metal part in the following ways:
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To flatten the entire part, if the Flat-Pattern1 feature is present, unsuppress Flat-Pattern1, or click Flatten 
on the Sheet Metal toolbar.
The bend lines are shown by default when you unsuppress Flat-Pattern1. To hide the bend lines, expand Flat-Pattern1, right-click Bend-Lines, and select Hide.
When you flatten the entire part in this manner, corner treatments are applied to create a clean, flattened sheet metal part.
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To flatten the entire part, if the Process-Bends1 feature is present, suppress Process-Bends1, or click Flatten on the Sheet Metal toolbar.
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To flatten one or more individual bends, add an Unfold 
feature.
For faster system performance, only unfold the bends that you need for the task that you are performing. For example, when you add a cut across a bend, only unfold that one bend.