design for six sigma

Six Sigma Process for Automotive Manufacturing

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There are slogans in the world that have become synonymous with a reliable, high quality product like “a diamond is forever” for diamond jewelry, “don’t leave home without it” for a reliable credit card and even “takes a licking and keeps on ticking” describing a durable watch. When you talk about automotive manufacturing the phrase ‘six sigma’ has become the standard way to express a quality manufacturing process.

The six sigma master minds

Six sigma did not always reflect the standard for automotive manufacturing quality. The six sigma mind set was started in the 1980s by several industry leaders including Bob Galvin, CEO of Motorola, Jack Welch, CEO of GE and Larry Bossidy CEO of Allied Signal which has since become Honeywell.   Galvin spearheaded the implementation of this process and challenged his two counterparts at Allied Signal and GE to follow suit. With this challenge each company began their six sigma initiatives that became the standard of high quality manufacturing. This standard then became the norm in all manufacturing sectors including automotive and was the only way to be competitive in the worldwide markets.

Understanding six sigma statistics

The concept of six sigma is based on the normal distribution curve in statistics which shows the variation in a product population and is graphed in a ‘bell curve’.   The area under the curve represents the product parameters and their distribution.

Figure 1  Normal distribution bell curve

Figure 1 Normal distribution bell curve

Once the production population has been charted the mean, or average of the population can be calculated. To calculate the mean of the population you add all the values in the population and divide by the total number of values. Once you have calculated the mean you can calculate the standard deviation. This calculation is slightly more complicated.  To begin you subtract the mean from each value in the population, then square the results and add all the values together. Finally, to get the standard deviation or ‘sigma’ value you divide the sum by the total population minus one.The result is the standard deviation or ‘sigma’ and is represented on the bell curve either above or below the population mean and encompasses a portion of the population. The six sigma population is plus three and minus three standard deviation from the population mean.

Automotive six sigma process

Understanding the distribution, mean and standard deviation of your process is great but how do you use this data to make your process better? The six sigma methodology starts with the idea that any part of the population that falls outside of the six sigma window requires some type of modification or correction to bring it back within the six sigma population. This is where the six sigma methodology comes in and begins to look at the opportunities within a process where things can go wrong and where you can make changes and improve the process.

DMAIC - foundation of six sigma

DMAIC – foundation of six sigma

The six sigma process follows these doctrines:

  • A manufacturing operation must strive to design a stable and predictable process that reduces sources of variation
  • Manufacturing process need to be monitored, kept in controlled and work towards continuous improvement
  • Quality improvement is the entire organization’s responsibility

The six sigma process is not just about making statistical calculations but instead is a culture within the automotive manufacturing industry and the key to designing a high quality process and continuously improving something that is key to being successful in the automotive industry.

Six sigma has been fully integrated into all aspects of the automotive manufacturing processes and is now recognized worldwide as the standard of quality that must be used to be recognized as a world-class level manufacturing process.

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