Six Sigma is a highly disciplined process that is used by companies who want to deliver near-perfect products and services. It does so by first focusing on systematically reducing process variation, after which it focuses on improving process capability.
Six Sigma (when used as a means to measure any particular process of a company) can be very effective at eliminating virtually every error. The normal practice is to measure only +/- 3 to 4 standard deviations from the mean, which can allow between 6,200 and 67,000 defects per million opportunities (DPMO). However, the process parameters used by those who employ Six Sigma are +/- 6 standard deviations (which generates only 3.4 DPMO) - almost perfect. This helps to ensure a consistent process, thereby delivering a consistent high-quality product.
That is the technical definition, but Six Sigma is much more. It is a means by which a company can attack all problems that it might encounter.
There are 2 major processes involved with a Six Sigma effort DMAIC and DMADV. Although these processes might seem similar at first, there are some major differences.
The DMAIC process (stands for Define, Measure, Analyze, Improve and Control) is an improvement system used for incrementally improving an existing product or process which falls below the specification limits (such as not meeting customer specification or inadequate performance). The steps involved in this process are:
1) DEFINE - Define the project goal and the customer needs (both
internal and external).
2) MEASURE - Measure the desired process to determine its current
performance.
3) ANALYZE - Analyze and determine the root cause(s) of any defects.
4) IMPROVE - Improve the process by eliminating the defects.
5) CONTROL - Control the future process performance.
On the other hand, the DMADV process (stands for Define, Measure, Analyze, Design and Verify) is an improvement system used to develop new products or processes at Six Sigma quality levels. These can be either new products that the company wants to develop, or an existing product or process that has already been optimized and still doesn't meet acceptable levels. The steps of this process are:
1) DEFINE - Define the project goal and the customer needs (both
internal and external).
2) MEASURE - Measure and determine customer needs and specifications.
3) ANALYZE - Analyze the process options to meet customer needs.
4) DESIGN - Design the process to meet customer needs.
5) VERIFY - Verify the design performance of the process and its ability
to meet customer needs.
One fairly recent Six Sigma effort that illustrates this process took place at EZ-Acres dairy farm (near Homer, New York). At this farm, an effort was launched to:
* Decrease variation in the diet given to the cattle (thought to be the variant involved with lower milk production).
* Reduce the cost of feed.
* Improve the safety factor levels used in the feed ration formulation.
By the use of this quality management program, its designers hoped to increase the long-term milk production of the farm's cattle. The steps EZ-Acres took was first to document the feeding system using a quality framework. Next, they used techniques (such as control charts) to identify sources of variation and determine which ones were potentially controllable. One controllable source found was that of purchased feed. Once this source was identified, it resulted in the creation of a preferred supplier list. After that, they determined the amount of variation in the feeds. One potential source identified was dry matter and composition. Finally, they took there collective data, and began developing a quality management program. An area that was identified here was the need to improve the feeders' technical skills. They discovered a need to train them in simple statistics, equipment maintenance and basic dairy nutrition.
This was a simple example of the effectiveness of quality processes, but Six Sigma can be used to improve any product, process or service in any field.
A company that is willing to make the effort to implement quality programs such as Six Sigma can expect to lower costs and increase profits - which is the bottom line.