Automotive Subassembly Engineers Face A Multitude Of Challenges
It used to be that automotive companies took ownership for all aspects of the finished vehicles
. Scores of engineers worked on the improvements and innovation that put American automotive companies at the top of the industry for decades. In todays market, however, automotive companies have evolved into professional assemblers. Automotive companies have passed the burden of design, performance, longevity, aesthetics, warranty, and most importantly, cost reductions, to their suppliers, and the suppliers in turn have passed much of this burden to their suppliers. The resulting shakeout has created some interesting dynamics for engineers, as they are weighed down with having to engineer sub-assembled products (such as specialty o-rings) which may or may not be in their specialty. Rubber and plastics often come into play in these circumstances, as both rubber and plastics are somewhat unique in the broad field of industrial engineering.The first consideration for engineers in this predicament is to qualify the physical demands of the application, for instance of automobile or aircraft o rings in a given program.
Automotive engineering is generally more complex than most industrial engineering, as there are so many physical, environmental, and longevity considerations, as well as numerous constraints. If the sub-assembled unit goes under the hood, for example, vibration, heat, cold, exposure to hydrocarbon oils or fuel must be considered. Since auto o rings as well as other rubber and plastics are normally used to control the flow of fluids or gasses, they must be engineered to seal out any foreign media. ASTM standards for tensile strength, elongation, heat aging, compression set, and media exposure have to be kept in line with performance requirements. There are several established specifications for rubber and plastic materials, depending on the OEM, and most will establish the specification and provide a drawing only. The required dimensions and associated tolerances of specialty rubber o-rings, for example, will also have an impact on material choice, as the processing method and tooling considerations can vary widely based on the material. It is then up to the project engineer for the sub- assembler to choose and qualify a material to meet this criterion.
The next step is to narrow down the material choices based on the physical demands of the application. Qualifying the physical requirements of the application will normally limit the field of materials. If the application demands high temperature resistance as well as resistance to hydrocarbon oils, for example, the only realistic choices are FKM or FS rubber. If the application demands high temperature resistance without hydrocarbon resistance, then silicone rubber will normally be suitable. If the temperature does not exceed 240F or so, then NBR or HNBR may be used, and thermoplastic materials may come into play. Once material choices have been filtered down and qualified against required specifications, the picture becomes much more finite. For additional information on automotive and mechanical engineering topics, please visit www.real-seal.com to learn more.
by: realseal