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Dimensional instability inherent to the extrusion process and the tolerance stack up due to bending and reshaping processes induce a part-to-part variation, which exceeds what is typically acceptable for an automated assembly process. Therefore, advanced forming methods such as stretch bending, hydroforming/calibration, etc., are required to provide tight dimensional tolerances. However, some of these technologies are relatively new, therefore, there is not an extensive knowledge base to assist the product and process designers working with aluminum extrusions. Several issues related to the design of extruded profiles, bending, friction and formability have to be resolved to increase the number of applications in the automotive industry. This paper reviews the manufacturing system including hydroforming technology and its application to extruded aluminum profiles. Several issues related to alloy selection, design, bending, friction and formability will be highlighted.

Recent studies in sheet metal forming, conducted at universities world wide, emphasize the development of computer aided techniques for process simulation. To be practical and acceptable in a production environment, these codes must be easy to use and allow relatively quick solutions. Often, it is not necessary to make exact predictions but rather to establish the influence of process variables upon part quality, tool stresses, material flow, and material thickness variation. In cooperation with its industrial partners, the ERC for Net Shape Manufacturing of the Ohio State University has applied a number of computer codes for analysis and design of sheet metal forming operations. This paper gives a few selected examples taken from automotive applications and illustrates practical uses of computer simulations to improve productivity and reduce tool development and manufacturing costs.

Designing the process sequence for deep drawing round cups is a trial and error process. The variations in the part geometry and processing conditions lead to a variety of problems that have to be solved after the dies and punches have been made. A system to design processes sequences is being developed at the Engineering Research Center for Net Shape Manufacturing (ERC/NSM). The system would help designers in developing the sequences, evaluating these sequences, and in predicting possible problems before production of parts. This would lead to a substantial savings in time and money. This system has three modules, a design module to design the process sequences, a finite element analysis module to simulate the forming process to predict possible problems when forming the part, and an interface module to handle data transfer between the two modules. The design module of the system is documented here.

Deep drawing and ironing are the major processes used today in manufacturing of most beverage cans from aluminum. The same technology is utilized in manufacturing of steel cans for the food industry. The practical aspects of this technology are well known and gained through extensive experimentation and production know-how. The fundamental aspects of the processes, however, are relatively less known, especially regarding the temperature developed during deformation and the effect of deformation speed upon temperatures and lubrication. Thus, it is expected that process simulations using FEM techniques would provide additional detailed information that could be utilized to improve the process conditions. This paper illustrates the application of process modeling to deep drawing and ironing operations. The predictions agree well with the experimental results.

Predominant failure modes in the forming of sheet metal parts are wrinkling and tearing. Wrinkling may occur at the flange as well as in other areas of the drawn part and is generated by excessive compressive stresses that cause the sheet to buckle locally. Fracture occurs in a drawn material which is under excessive tensile stresses. For a given part and blank geometries, the major factors affecting the occurrence of defects in sheet metal parts are the blank holder force (BHF) and the blank holder pressure (BHP). These variables can be controlled to delay or completely eliminate wrinkling and fracture. Modern mechanical presses are equipped with hydraulic cushions and various advanced multi-point pressure control systems. Thus, the BHP can be adjusted over the periphery of the blank holder as a function of location and time (or press stroke).