Dimensional Quality Control of Repeated Molded Polymer Battery Cell Housings in Automotive Energy Systems

摘要

Current manufacture of alternative energy sources for automobiles, such as fuel cells and lithium-ion batteries, uses repeating energy modules to achieve targeted balances of power and weight for varying types of vehicles. Specifically for lithium-ion batteries, tens to hundreds of identical plastic parts are assembled in a repeating fashion; this assembly of parts requires complex dimensional planning and high degrees of quality control. This paper will address the aspects of dimensional quality for repeated, injection molded thermoplastic battery components and will include the following: First, dimensional variation associated with thermoplastic components is considered. Sources of variation include the injection molding process, tooling or mold, lot-to-lot material differences, and varying types of environmental exposure. Second, mold tuning and cavity matching between molds for multi-cavity production will be analyzed. The application of 3D scanning technology for mold duplication and tuning will be described. Finally, unique aspects of assembly variation modeling of assembled components from multiple cavities will be addressed. Parts with multiple mating features from multi-cavity molds require special statistical modeling to accurately evaluate assembly combinations and their potential to exceed specified tolerances. Quality monitoring also requires care to evaluate streams of variation inherent in multiple-cavity molds.