The aim of the presented study is to analyze the causes of a leakage type failure occurring in a servo drive plastic housing and to identify the design and process factors that contribute to its formation. Based on a Design FMEA, which classified the housing leakage as a critical failure mode with a high Risk Priority Number (RPN = 196), a numerical simulation of the injection molding process was performed using the NX EasyFill Analysis environment. The simulation included filling, packing, and cooling analyses, while key parameters such as temperature fields, pressure distribution, weld line formation, air traps, Frozen Layer Ratio, and volumetric shrinkage were evaluated. The results showed that the leakage is caused by a synergistic combination of several phenomena, particularly cold weld lines near functional surfaces, non-uniform solidification of the material, significant thermal inhomogeneity, locally increased shrinkage, and insufficient pressure coverage in remote areas of the cavity. Based on these findings, specific design and process measures were proposed, focusing on optimizing wall thickness, rib geometry, gate location, venting, mold cooling, and adjusting injection molding parameters. The results confirm that numerical simulation combined with the FMEA methodology represents an effective tool for reducing the risk of failures already in the design phase and significantly contributes to improving the reliability and service life of servo drives.
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