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For many years, the use of in-mold fasteners has been avoided for various reasons including: not fully understanding the load cases in the part, the fear of quality issues occurring, the need for servicing, or the lack of understanding the complexity of all failure modes. The most common solution has been the use of secondary operations to provide attachments, such as, screws, metal clips, heat staking, sonic welding or other methods which are ultimately a waste in the process and an increase in manufacturing costs. The purpose of this paper is to take the reader through the design process followed to design an in-molded attachment clip on plastic parts. The paper explores the design process for in-molded attachment clips beginning with a design concept idea, followed by basic concept testing using a desktop 3D printer, optimizing the design with physical tests and CAE analysis, and finally producing high resolution 3D prototypes for validation and tuning.

An L16 orthogonal array parameter Design of Experiment (DOE) evaluated six design parameters of the mating thread interface between the exhaust manifold outlet flange and jointing stainless steel fastener. The objective of this study was to identify optimal parameters for the redesign the thread interface by ensuring 100% seating of the fastener into the manifold flange (here after referred to as stud seating). Since the current fastener and manifold outlet flange interface threads do not always achieve the design objectives, due in part to a form of abrasive wear, consideration was given to develop a testing strategy that would quantify the amount of remaining thread engagement for a given stud length. This testing strategy ensured that the control parameters considered in this experiment would reveal main effects and interactions between the stud and tapped hole threads thus providing the necessary parameters for the redesign on the joint threads.