Many times we have received calls from confused users asking whats going on here? when using lofted bends in sheet metal.
From the Knowledge base Solution ID : S-056138
Flat patterns for sheet metal parts created using lofted bends are incorrect. Why does this happen?
When using lofted bends it is usually a good idea to turn off the simplify bends option in the flat pattern feature.
-Right-click on the flat pattern feature->Edit feature->Uncheck Simplify bends
This also be turned off at the document properties level but this will need to be done prior to creating any sheet metal features for it to be applied to the flat pattern.
-Tools->Options->Document Properties->Sheet Metal->Simplify bends
If you look bellow you can see the result of leaving this option on. SolidWorks goes and straightens these curved edges.