Sheet metal bend lines show up in my assembly.  When I open an assembly that contains bent sheet metal components, all the bend lines are showing.  I can make the bend lines go away by opening the various sheet metal part models and then closing them.  This can take a while if there are a lot of sheet metal parts in an assembly.  Additionally, the bend lines only show up on parts that have been flattened at some point.  If I flatten the sheet metal part by clicking the "flatten" button in the part file and then unflatten it by clicking the "flatten" button again then the bend lines show in the assembly.  As well, if the sheet metal part has ever been brought into a drawing and had a flat pattern shown then the bend lines show in the assembly.  If the part has never been flattened, either in the part file or in a drawing, then the bend lines do not show up in the assembly.  Any thoughts??