Case Study: CPK

Industry: Manufacturing

Background: This company provided engineering and manufacturing development of Nacelles (housing for jet engines) for commercial aircraft. During the development phase of the product lifecycle, troves of inspection data were captured in some pretty elaborate excel workbooks by the internal quality group. Envision a workbook that has 50-100 pages, each with  5-10 images (usually 3d CAD screenshots) along with unique numbers pointing to the individual features to be measured. There were over one hundred workbooks spread across various folders that documented the quality for each nacelle that was assembled over the previous 5 years. When someone needed to find any quality information on a specific unit, at a specific stage of the build– normally opening one of the workbooks could answer the question. However, it was frustratingly difficult to look at the same features over time and answer questions such as: Is our quality in that area getting better or worse- if a feature is out of tolerance is it always to the high side or low side –  are there certain areas or sections of the Nacelle that have poor quality where maybe the cause is with a specific supplier part. And these were the questions that everyone was wondering…

Tool: Excel, VBA, Power Query, Power Pivot

• • • Using VBA linked into the hundreds of archive workbooks, and created a usable database of each inspection point, date/unit measured, etc.
    • Created new inspection template and guidelines so future workbooks could be downloaded into power query without VBA.
    • Created an Analysis tool where the user could select any inspection point or group of points then it would 
      • calculate Process Capability (cPK)  along with a normal distribution visual.
      • Display a time series showing the target value, Upper Spec Limit (USL), Lower Spec Limit (LSL), and actual measurements.

Results

• The tool was used to solve multiple “chronic” quality problems prior to full rate production.
• The tool was demoed to our customer Airbus and implemented as a company development standard going forward.