As in any engineering component, manufacturing a bipolar fuel cell plate for a polymer electrolyte membrane (PEM) hydrogen fuel cell power stack to within its stated design tolerances is critical in achieving the intended function. In a bipolar fuel cell plate, the dimensional features of interest include channel width, channel height, channel parallelism, side wall taper, straightness of the bottom or side walls, plate parallelism, etc. Such measurements can be performed on coordinate measuring machines (CMMs) with micro-probes that can access the narrow channels. While CMM measurements provide high accuracy (less than 1 μm), they are often very slow (taking several hours to measure a single plate) and unsuitable for the manufacturing environment. In this context, we describe a system for rapid dimensional measurement of bipolar fuel cell plates using two laser spot triangulation probes that can achieve comparable accuracies to those of a touch probe CMM, while offering manufacturers the possibility for 100% part inspection. We discuss the design of the system, present our approach to calibrating system parameters, present validation data, compare bipolar fuel cell plate measurement results with those obtained using a Mitutoyo UMAP (see footnote 1) fiber probe CMM, and finally describe the uncertainty in channel height and width measurements.
We describe the application of several surface profile filters as an enabling tool in the dimensional measurements of an engineering artifact, namely, a fuel cell plate. We recently reported work on the development of a non-contact system for dimensional metrology of bipolar fuel cell plates. That system is comprised of two laser spot triangulation probes that acquire profile data across a plate. While the non-contact system provides rapid measurements (measurement speed of 100 mm/s to 500 mm/s), the data are noisy and cannot be used directly to obtain features of interest such as channel depth and width. In this paper, we show how different surface profile filters such as the spline, morphological, and robust filters, can be employed to identify and suppress outliers and to produce a mean line that serves as a substitute geometry from which we can determine features of interest. Further, we compare the non-contact probe data against contact probe measurements made using a coordinate measuring machine (CMM). Surface profile filters are again useful in correcting the reference data for tip size and also in removing any free form deformation in both data sets prior to parameter evaluation and comparison.
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