To create a three bend corner you can use corner seam or auto miter.
Inventor sheet metal corner seam.
About sheet metal parts.
On the ribbon click sheet metal tab modify panel corner seam.
You can create a corner seam or rip an existing corner seam between sheet metal faces.
An automatic corner feature occurs when you create two flange features using identical parameters on adjacent edges of a sheet metal face.
Specify any of the following in the corner edit dialog box.
To specify an overlap that differs from the value specified select overlap type in the corner edit dialog box.
Create corner seam between sheet metal faces create seams between faces that intersect or are coplanar.
Click the corner edit glyph for your selected corner.
To create a three bend corner you can use corner seam or auto miter.
The default settings for the sheet metal rule define the default values for the options.
You can change the values for an individual corner.