Applications involving high electrical conduction require complex components that are difficult to be manufactured by conventional processes. Laser sintering (LS) is an additive manufacturing technique that overcomes these drawbacks by offering design flexibility. This study focuses upon optimizing the process of laser sintering to manufacture functional prototypes of components used in high electrical conduction applications. Specifically, components for two systems – high current sliding electrical contacts and fuel cells – were designed, manufactured and tested. C-asperity rails were made by LS and tested in a high current sliding electrical setup. Corrugated flow field plates were created by LS and their performance in a direct methanol fuel cell (DMFC) was tested. This is the first experimental attempt at using laser sintering for manufacturing such complex components for use in high electrical conduction applications.The second part of this study involves optimization the laser sintering process. Towards this, efforts were made to improve the green strength of parts made by LS. Particle size of graphite/ phenolic resin and addition of nylon/11 and wax were tested for their effect upon green strength. Of these, significant improvement of green strength was observed by altering the particle size of the graphite/ phenolic resin system. New methods of improving green strength by employing fast cure phenolic resins with carbon fiber additions were successfully demonstrated. This study also identified a binder system and process parameters for indirect LS of stainless steel –for bipolar plate compression/ injection mold tooling. All the experimental results of this study lead us to believe that laser sintering can be developed as a robust and efficient process for the manufacture of specialized components used in advanced electrical conduction systems. text
Engineering, Industrial, rapid tooling, injection molding, stereolithography, laser sintering, ejection force, and coefficient of static friction
While manufacturing is typically considered a high-volume industry, the necessity for small quantities of products and components exists for aerospace customers and those producers wishing to mass customize their products. Because of the high cost of tooling, injection molding processes are seldom used to produce only small quantities of parts. This, however, can be remedied if cost effective tooling methods are implemented. Rapid prototyping processes show great potential for such tooling applications because they generally require shorter lead times, produce less waste, and, in some cases, use less expensive materials. The research presented herein studies the feasibility of using injection mold inserts produced with additive methods by investigating ejection and friction. Through experimentation, the application of P-20 steel, laser sintered LaserForm ST-100, and stereolithography SL 5170 tools to produce limited quantities of a thin-walled cylindrical part are explored. A substantial amount of data and statistical analysis are provided that reveal conditions during the actual injection molding process, and comparisons are made among the three insert types. Experimental ejection forces from each tool type are compared with model-based calculations, and apparent coefficients of static friction are calculated and compared to standard test results. Based on the data and analyses, the benefits and limitations of using rapid tooled injection mold inserts are presented.