VPA and New Indices for Quantifying Sheet Quality and Troubleshooting, PaperCon '09 Conference

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Sheet properties measured both on-line and off-line are often expressed in arrays of values that are called “profiles” in cross-machine direction (CD) and “trends” in machine direction (MD). Traditionally, standard statistical metrics and variance partition analysis (VPA) have been used to quantify the variability of sheet properties. With the computing power, memory capacity, and display technology available in today’s quality control and mill-wide systems, a new set of indices and two-dimensional analysis methods can be useful for better quantifying sheet quality and provide more insights for troubleshooting sheet-making processes. This paper summarizes the commonly used VPA calculation and introduces a new set of indices for analyzing two-dimensional sheet quality measurements.