Applications of profile filtering in the dimensional metrology of fuel cell plates

Abstract

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.

Evaluation of a multi-sensor horizontal dual arm Coordinate Measuring Machine for automotive dimensional inspection

“…It has been stated that CMM mounted laser scanners are at least one order of magnitude less accurate than touch trigger probe [6]. Although, more recent studies have found an improvement is laser scanner accuracy [3,5], which this study has also found. Considering measurements against a known diameter, the touch trigger probe measurement results deviated by at worst 16.7 μm compared to 27.1 μm when the sphere diameter was measured with the laser scanner.…”

“…To do this, the vector crossproduct was calculated using the x-axis vector and a vector formed by the line between the two rear datum plates, (2). The vector cross-product between the xand z-axes was then used to form the y-axis, (3). The x-, yand z-axes unit vectors were then combined to form the transformation matrix R, (4).…”

“…Accurate measurements are important in being able to monitor production processes and ensure conformity to design specifications [1]. In the automotive industry, inspection of key dimensional and geometrical tolerances is typically done using a coordinate measuring machine (CMM) [2,3]. Traditionally, a touch trigger probe has been employed as the CMM sensing mechanism because of well-established calibration processes and knowledge of measurement uncertainties [4,5].…”