During stamp or panel forming the two primary control elements used to control the flow of the blank into the die cavity are the blank holder and the draw beads. Many researchers have investigated the use of both control elements either used by themselves or together. In addition, these investigations go in cycles of being of interest to researchers and industry. The preferred control elements also seem to go in cycles, alternating between draw beads and blank holders. Recently, there has been increased interest in the basic mechanics and control during stamp forming. This paper compares control, both open-loop and closed-loop stamp forming processes using draw beads and blank holders.

Of particular interest are the modes of failures. Sheet tearing can occur whether the process is controlled using either draw beads or blank holder force. However, other defects such as wrinkling and galling may also occur. For instance, improperly supported blanks, or blanks that have insufficient blank holder forces at critical locations may result in wrinkling in the flange. On the other hand, the use of draw beads may result in draw bead end effects so that there are small wrinkles formed at the end of the draw bead due to the blank not being supported in this region and furthermore, there may be galling of the blank downstream of the draw bead end where the blank is approaching the die shoulder. In addition, the blank near the draw bead end is where tearing frequently also occurs.

So, for this paper the advantages and disadvantages of controlling the stamp forming process for an oval aluminum pan will be explored. Rather than categorizing draw bead or blank holder control being the best method for controlling stamp forming, this paper will have used a more nuanced approach to the topic. Consideration of regional control for the forming process with respect to open- and closed-loop control for stamp forming, wrinkling, tearing, and the forces generated in selected regions of the pan during forming, the generation of flange wrinkling and galling on the blank, and strains in selected regions.

This paper is the last in a long series of papers by the author published by ASME on stamp forming. Some of the figures and literature from previously published material will be presented but the discussion and analysis has not been presented before. In addition, there will be new results presented, especially with respect to local force control that will be new and useful for researchers in academia and industry that has not been previously presented which addresses the nuanced approach to control of the forming process that is being advocated.

A description of the equipment, material properties of the blank, a brief summary of process control and procedures will be provided as part of this paper, photographs will be used to highlight galling and wrinkling as part of the results section.


Stamp Forming: A Comparison in the Use of Draw Beads and Blank Holder Force for Producing Aluminum Panels

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Aerospace, Bioengineering, Applied Mechanics, Design Engineering Division, Advanced Energy Systems, Manufacturing Engineering Division, Noise Control and Acoustics, Nondestructive Evaluation, Diagnosis, and Prognosis (NDPD), Nuclear Engineering Division, Process Industries Division, Fluids Engineering, Heat Transfer, Materials, Microelectromechanical Systems, Safety Engineering and Risk Analysis, Computers & Information in Engineering


Paper Proceedings: https://asmedigitalcollection.asme.org/IMECE/IMECE2020/volume/84478

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