A case study in application of robust design methods to waterjet processes in overhaul and repair of jet engine components

Abstract

The North Berwick Engine Services (NBES) Business Unit at the Pratt & Whitney (PW) facility in North Berwick, Maine has identified the need to develop new for cleaning/stripping parts in the overhaul and repair cycle of jet engine components. I investigate the issues that must be answered for the introduction of a new cleaning technique. The new method uses a waterjet in place of a wet abrasive blast using a novaculite slurry solution. The process used to develop high-pressure waterjet cleaning procedures was based on Robust Design methodology. Robust Design uses orthogonal arrays which allow a large number of variables to be studied with a small number of experiments. This requires selection of key input factors that affect the output characteristics of the product. A set of experiments with seven control factors were run in order to determine the response to two quality characteristics: material erosion and increase in surface roughness. Optimum settings for each one of these seven control factors were established. A verification experiment was run in order to validate predictions made based on the optimum settings. It is estimated that this new cleaning method will yield $1,730,000 of savings over the next five years, eliminate four hours of labor per part, and increase production capacity by two additional person-­years.