Measurement System Analysis More Than a Line on a PPAP Submission
For those of us in the manufacturing world, measurements on products and processes are all important to ensure the products will meet customer requirements, perform correctly, safely, and for a reasonable lifespan. We place our faith in the measurements to accept or reject product—or to adjust the manufacturing process. But are the measurements correct—and how would we know? There is nothing to be gained by using a measurement process or gage that gives five different results when the same characteristic is measured five times!
In his book, “Economic Control of Quality of Manufactured Product,” published in 1931, Dr. W. A. Shewhart opens chapter 23 with these words, “In any program of control, we must start with observed data; yet the data may be either good, bad, or indifferent. Of what value is the theory of control if the observed data going into the theory are bad?” Dr. Shewhart recognized that poor data can lead to poor decisions. In the world of inspection, poor measurements can lead to poor decisions or results—products that do not conform to specifications or processes adjusted incorrectly, or that unintentionally escape to the end customer.