Dean of Springs
Do You Know Your Quality Numbers? By Dan Sebastian
What is your cost of quality return rate in dollars as a percentage of sales? What is your defect rate in PPM (parts per million)? Do you know the critical characteristics of the parts you are making? Do you use the statistical measures of the critical characteristics (standard deviation σ)? What is the process potential index (Cp) and what is the process performance index (Cpk)? commitment to the quality of our product. As we looked at our quality measurements, we saw that there was a complete lack of control. At first, I was confused by this issue, as we had some of the best setup people and operators in the business and they were measuring parts and adjusting for out of the center point of the characteristic being measured. We turned to the teachings of Shewhart, Deming and Juran (the Ford quality people pointed us in the right direction).
The Basics The journey to establish a consistent quality process that gave us the parts our customers required started with the basics. As we studied the problem, we realized we did not
0.400.35Probability Density
T
he early 1980s was a turbulent time for the auto industry. Chrysler was being bailed out by the government, while General Motors Corp. and Ford were losing a large share of market to the Japanese auto companies because of inadequate quality from U.S. manufacturers. The problem was deeply rooted and began after World War II. During the war, U.S. manufacturers were pressed into high volume manufacturing to support the war effort. The war boards set up by the Roosevelt administration established the Emergency Technical Committee for American War Standards. They went to W. Edward Deming and Joseph Juran to establish a quality program. Both Deming and Juran had worked with Walter Shewhart of Western Electric (also Bell Labs), who pioneered the use of statistical quality control methods. The programs were enormously successful. After the war, American companies began to be run by non-technical people, who turned to efficiency experts (modern-day lean managers) who saw the time used to perform quality checks as wasted time. In large measure, these quality checks were abandoned, which brought us to the quality crisis of the 1980s. I arrived at the Associated Spring valve spring operation on a cold snowy day in February 1982. My assignment was to “fix a few minor problems with inventory and production issues.” As I began to assess the problems, it was apparent that what we faced was a lot more than anyone anticipated. I went to my engineering roots and formed a Pareto diagram of the many problems we had to address. It started with an evaluation of the inventory issues. As in any good plan, I had to first deal with a significant distrust between managers and union employees. As we began the arduous process of rebuilding trust, we were hit by a notice from Ford that we were being decertified as a vendor. After a series of meetings with Ford quality and procurement people and a serious look at the inventory issue, it was apparent that the root cause was a complete absence of both an understanding and
0.30-
68.27%
0.250.20-
95.45%
0.150.10-
99.73%
0.050.00-
µ-3σ
µ-2σ
µ-σ
µ
µ+σ
µ+2σ
µ+3σ
Dan Sebastian is a former SMI president and currently serves as a technical consultant to the association. He holds a degree in metallurgical engineering from Lehigh University and his industry career spans more than four decades in various technical and management roles. He may be reached by contacting SMI at 630-495-8588.
SPRINGS / Fall 2020 / 17
