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Because it is common to attach plastic parts to other plastic, metal, or ceramic assemblies with mechanical fasteners that are often stronger and stiffer than the plastic with which they are mated, it is important to be able to predict the retention of the fastener in the polymeric component. The ability to predict this information allows engineers to more accurately estimate length of part service life. A study was initiated to understand the behavior of threaded fasteners in bosses molded from engineering thermoplastic resins. The study examined fastening dynamics during and after insertion of the fastener and the effects of friction on the subsequent performance of the resin. Tests were conducted at ambient temperatures over a range of torques and loads using several fixtures that were specially designed for the study. Materials evaluated include modified-polyphenylene ether (M-PPE), polyetherimide (PEI), polybutylene terephthalate (PBT), and polycarbonate (PC).

When GE Plastics entered the multi-process multi-material arena with the construction and installation of Alpha I in its Pittsfield, Mass. headquarters, it recognized that if plastics are to continue to provide revolutionary products, the industry must expand its thinking beyond current single process applications. Multi-process parts must be developed to demonstrate to the automotive industry a new generation of applications. The purpose of this paper is twofold: to explain the value of multi-process multi-material technology and to present an engineering analysis of the system which addresses design and processing questions.