1. A method of forming a hemming tool, the method comprising: providing a computer generated model of a panel including a flange in an unhemmed position and of a hemming tool; virtually simulating hemming the flange in the unhemmed position with the hemming tool in the computer generated model; identifying at least one non-conformity along the flange in the computer generated model after virtually simulating hemming; modifying the computer generated model to a modified computer generated model by adjusting the flange to change the at least one non-conformity; virtually simulating hemming the flange in the unhemmed position in the modified computer generated model with the hemming tool in the modified computer generated model; and wherein the hemming tool in the computer generated model includes a hemming surface and wherein modifying the computer generated model includes adjusting the hemming surface based on the flange in the modified computer generated model, and further comprising fabricating the hemming tool to include the hemming surface of the modified computer generated model.