Some characteristics of enhanced Marciniak device useful in the experimental determination of forming limit diagram are presented. Combined with the utilization of CCD camera for image capture of the tested specimen and the image analyzing software, the forming limit diagrams and forming limit stress diagram may be obtained. Because in the area of biaxial stretching some materials show unexpected behavior, a series of elliptical punches was designed. Also, in order to extend the forming limit diagram in the region of negative minor principal stress, a special "X" shaped punch was used.
