Economic Analysis of Hydro-Mechanical Sheet Metal Forming 1999-01-3207
Recent industry trends have resulted in growing interest among automakers in low to medium volume manufacturing. The expansion of automobile production into developing economies and the desire to produce specialized vehicles for niche markets have pressed the automakers to find cost effective solutions for manufacturing at low volumes, particularly with regard to sheet metal forming. Conventional high volume stamping operations rely heavily on achieving minimum scale economies which occur at about 200,000 parts per year. These scale economies are mainly dictated by the efficient use of the standard, expensive cast iron dies. These dies can cost well over one million dollars depending on the part, and in return offer tool lives over 5 million strokes.
Die investment can be reduced by changing the stamping process technology. Hydro-mechanical forming has been proposed as a promising low volume alternative to conventional stamping. This technology has a slower cycle time than stamping, which in turn limits its applicability to low production volumes. However, hydromechanical forming offers the advantage of greatly reduced dedicated tooling investment. Furthermore, hydro-mechanical forming offers other advantages over stamping such as the potential for reduced part weight in some applications and a reduction in production lead times.
The hydroforming step uses only a punch and does not need a female die. Expensive and time consuming die set adjustments and tryout are also significantly reduced. That in turn reduces operations , and although it uses expensive equipment, it does not require any die investment at all. Flanging is accomplished in exactly the same way as for conventional stamping operations, and thus has no effect on the cost.
This paper presents an economic analysis of the process with particular emphasis places on the tradeoff between die investments and production cycle times. The analysis indicates that hydro-mechanical forming can be cost effective at volumes up to 60,000 parts per year.