Quality of trimming and its effect on stretch flanging of automotive panels

Traditional trimming requires accurate alignment of the die shearing edges, typically 5-10% of the blank thickness. Increasing the clearance above the recommended value often leads to generation of burrs on the trimmed surface. These burrs may create difficulties for flanging and hemming operations. Details of trimming technology for panels made out of aluminum sheet AA6111-T4 with elastic offal support will be discussed, including such factors as die radii of the tooling, effect of tooling wear, and trimming angle on the quality of trimmed surface. Also, imperfections on the trimmed edge of the panel may result in reduced formability in stretched flanging and hemming operations. Experimental results quantifying the behavior of trimmed surface in stretching will be provided for both a conventional trimming process and a newly developed process.