Original Date: 05/01/2000
Revision Date: 01/18/2007
Information : Statistical Process Control
Northrop Grumman Defensive Systems Division (DSD) has applied Statistical Process Control (SPC) to the evaluation and analysis of test result data. The measurement of key product characteristics is automated, and the data is treated as SPC data points. The data points are compared to historical control limits as well as specification limits to determine if any are considered out of control. Out-of-control data points are automatically identified and then addressed by Operations Engineering. Control limit updates are made based on changes in the process variability and when a significant amount of data has been collected. The SPC system provides a method for collecting real-time data and enables real-time assessment of product quality.
Past process control and variability reduction methods were managed using labor-intensive manual data collection and analysis methods. Northrop Grumman DSD’s introduction of a fully integrated SPC system into the main production floor was completed in 1994, and is currently being expanded to other shop operations areas. The SPC system can display control charts on-line with detailed drill-down information by assembly, serial, material, or lot number. These charts are displayed at the end of each batch. Users can add/edit comments to the individual control chart points to identify information relevant to the process. The system also can be set up to prevent further processing until corrective action is addressed. The chart advisor is an on-line data analysis graphical and report interface for performing data analysis calculations and displaying output (e.g., Pareto, histograms) from the SPC system.
Since implementing the SPC system, Northrop Grumman DSD has realized several benefits. Among these are reduced rework and repair time; facilitation of systematic process improvement initiatives; and decreased cycle time and costs attributed to timely identification of out-of-control processes.
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