Original Date: 04/01/1993
Revision Date: 01/19/2007
Information : SPC Applications in Assembly Hole Drilling
Prior to 1989, McDonnell Douglas Aerospace (MDA) was experiencing problems and subsequent rework of various fastener holes in assemblies in the commercial and Titan IV missile applications. To determine where the problem was occurring and ascertain the root cause of the problem, MDA instituted an SPC procedure.
The initial investigation by quality engineers revealed that improper hole preparation by the personnel appeared to be the cause of the problem. Consequently, a training plan was developed and all personnel involved in hole drilling and preparation were given 24-40 hours of training in SPC processes. The strategy employed was to define and standardize the hole drilling process, conduct a measurement system analysis, establish a data collection system, and ultimately achieve process control.
Personnel involved in the process soon discovered that each had a different method and technique for drilling and inspecting the holes. Data was collected that revealed the variability of the process. When the employees saw this variability, they developed a standardized drilling process that reduced some of the variability due to operator technique. The next step was to purchase a data collection system that was easy to use on the shop floor and would automatically record and display various statistical charts to the personnel. MDA purchased a Genesis QA 3000 computer manufactured by Quality Measurement Systems. The measurement device was also changed from a Mahr hole gauge to an electronic digital indicator, a remote transducer and Dimentron Plug Gages that could be coupled to the Genesis system. Data gathered from the use of these systems revealed further variability in the hole sizes. Corrective action was taken to standardize the drilling tools and equipment. This standardization further reduced variability.
The benefits derived from this SPC approach have helped MDA to baseline, improve, and standardize hole drilling procedures. It has developed and implemented tool kits for the shop floor, baselined and standardized gaging processes, and developed and implemented SPC data collection systems. The net result of this effort was a 42% reduction of hole drilling non-conformance in aircraft and a 65% reduction of hole drilling non-conformance in Titan IV.
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