A quantitative decision-making approach for assisting in the selection of manufacturing processes, applied to cutting of extrusions for automotive aluminum spaceframes

摘要

For the past ten years, Alcoa has supported a comprehensive program to design and develop advanced manufacturing techniques for the fabrication of aluminum intensive vehicles. AIV's, as they are called, are considerably lighter and thus more fuel efficient than today's steel vehicles. Because cars traditionally have been made of steel, the manufacturing methods employed with this material have evolved into very mature technologies. But, the inherent differences between steel and aluminum prevent the direct applications of these technologies to the fabrication of aluminum. Alcoa's current investigations focus primarily on a spaceframe concept. The spaceframe idea is to build vehicles by welding cast components and extruded lineals in a truss configuration. Traditionally, cars have been assembled from steel sheets by resistance spot welding. Aluminum spaceframes will be fabricated mainly by gas metal arc welding (GMAW) with robots. After extensive cooperative development efforts with Alcoa, a major European car company has decided to introduce a spaceframe based aluminum intensive vehicle in the early 90s. Alcoa will be the supplier of the cast and extruded components of this vehicle, as well as a select number of robotically welded subassemblies. At the present time, Alcoa is in the process of constructing a manufacturing plant in Germany, which will produce castings, extrusions and welded subassemblies for automotive aluminum spaceframes. In the plant, the castings and extrusions will be fabricated and thermally treated in discrete manufacturing centers from which they will be conveyed to a central surface cleaning facility. After surface cleaning, some of the parts will be moved to the plant's welding assembly line for fabrication of subassemblies and the remaining parts will be shipped to Alcoa's automotive customers. When selecting some of the manufacturing processes and preferred systems' vendors for the plant, a broad and complex range of issues had to be considered through application of a diverse assortment of expertise and perspectives. This was addressed by complementing the conventional qualitative decision- making methodology with a refined quantitative decision-making tool. By assisting each of the team members in systematically reviewing and analyzing all pertinent considerations and confirming, or substantiating, their individual preferences, a more systematically rationalized collective decision-making process resulted. This article presents the principles of the quantitative decision-making approach and illustrates an actual case where it was used to assist in comparing between the laser and the blanking processes, for cutting extrusions in the new plant. This approach, which can be utilized by individuals and teams in a great number of endeavors (e.g., R&D, engineering, sales, purchasing, etc.), has already been applied to selecting a surface cleaning systems supplier, a type of data management system, and the associated software for the plant.