Characterization of the injection molding process of passive vibration isolators

Abstract

This article discusses the variability of the mechanical properties (static stiffness, dynamic stiffness, and loss factor) observed in engine mounts used to isolate vibration caused by the engine in recreation utility vehicles. To avoid passenger’s discomfort during engine operation, it is important that the isolation provided by each passive vibration isolator be constant. Transmitted forces should also be minimized to prevent excessive structural stresses in the vehicle. Quantifying how human and machine molding parameters affect the performance of the final product is fundamental. The isolators studied in this article are produced through manual cycles of an injection molding process. This work provides a better understanding of the discrepancies on mechanical properties occurring during the industrial process. Curing temperature (T) and curing time (D) were found to be the significant machine parameters. Response surface methodology shows a nonuniform distribution of the solutions across the whole experimental space. A linear model of the output variables appears to be sufficient to achieve an optimization since linear coefficients are prevalent over quadratic or interaction coefficients. A proposed empirical model enables the determination of a set of curing parameters corresponding to specific required properties. The model also shows that, for a polychloroprene rubber mix, the variability of the mechanical properties can be reduced by increasing the curing parameters (T and D) used during current molding procedures. Finally, the numerical results helped getting a better understanding of how manufacturing parameters can influence the optimization process of elastomeric product properties. Improved production parameters and control standards can be established from this case study.