You can break sharp corners in NX Sheet metal by rounding or chamfering as shown in the figure.

Tutorial: break the sharp edges as shown in the figure
- Start the “Break Corner” command.
- Home Ribbon Bar => Corner Group => Break Corner
- Menu => Insert => Corner => Break Corner
- Select the edges to break.
Note: You can select all edges of the sheet metal:- Drag the mouse from one side to another side over the model. All the edges in the frame will be selected automatically.
- Press “Ctrl+A”
- Set the Breaking Method as Blend or Chamfer.
- Type the value of the Radius or Chamfer box.
- Click the “Ok” button or click the middle mouse button to break corners and exit from the command.