Six Sigma Manufacturing Example
Businesses who are not very active in quality management most of the time have a process quality from 2 or 3 sigma. This means a failure of about 66.700 products per million opportunities. At first sight, this looks really nice.
But let's look at a product that is built in 10 production steps. In every phase the amount of good products decreases:
- After 2 production phases: 870.862.
- After 4 production phases: 758.401.
- After 10 production phases, there are only 500.895 good products left. Surely this is normally unacceptable...
If you can achieve a sigma of 5, after the 10 production phases the amount of good products would still be 997.702.
The rejected products went down from 49,9% to 0,23% per one million opportunities. This example shows that such businesses should aim at a sigma from 5 or six... And also that the more production steps you have, the more this demands from your sigma level.