A NEW QUALITY METHODOLOGY AND METRICS FOR SPRAY PATTERN ANALYSIS

Abstract

A new quality procedure and metrics for detecting quality problems in various applications, including medical device coating, spray drying, mass spectrometry, inhalation (drug delivery), heat transfer, and combustion, is presented. The novel spray characterization method facilitates the evaluation of data relating to spray surface area, spray density distribution, and/or mass distribution by visualizing deviations (spray errors) with respect to an ideal distribution in a two-dimensional plane. In this paper an optical patternation experiment was performed using a custom diagnostic system based on a 2D laser light sheet (Mie scattering) technique to control the quality of a series of air-assisted micronozzles for medical device coating. The novel spray error metrics were evaluated and compared to traditional quality measures such as the pattern index (P.I.). It was noted that the new spray error patternation methodology and error metrics SEt, SEo, and SEu provide a more informative indicator than conventional measures for detecting the spray quality. Besides the spray symmetry, the spray size and accurate location and type of spray density deviations are assessed. The results show that by obtaining quantitative information on spray density deviations, nozzle comparability is facilitated, and otherwise- "invisible" spray under-representation and/or over-representations are detected. A new insight into the spray characteristics of a series of micronozzles could be gained.