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A CAE simulation methodology was developed to predict the warpage and shape deviation from nominal in finished plastic sub-assemblies that are joined using Infra-Red (IR), hot-plate or vibration welding processes. An automotive glove box bin and door sub-assembly was used to develop the methodology. It was seen that part warpage from injection molding and welding causes warpage in final assembled product which results in gaps and the consequent loss in quality of appearance. The CAE simulation methodology included prediction of the part warpage with residual stress from the injection molding process, use the post-molded shape as an initial part condition for the welding process, and simulation of the welding process itself.

Injection molding tools are expensive and the fatigue failure during production would result in very costly rework on the tool and downtime. Currently, mold designs are mostly based on expert experience without a careful stress analysis and the mold tool life cycle relies largely on rough estimates. The industry state of the art applies averaged temperature change and peak pressure load on the mold tool. The static analysis is then performed. Mold temperature history and thermal shock are not considered in the durability analysis. In this paper, a transient thermal analysis of the tool is performed in conjunction with the injection molding process simulation. The spatial and temporal variation of temperature, pressure and clamping forces are exported from Moldflow simulation. These histories of temperature and pressure are converted to appropriate loading curves and mapped into Abaqus FEA model.