After the long summer holidays M4E is back! I hope you had a really good summer. To get back on track with our issue #55, today we are going to introduce one methodology that originated in Motorola in the 1980s and has since helped many quality and production departmens around the world in order to reduce process variability and decrease defects, aiming for no more than 3.4 defects per million opportunities. We are talking about Six Sigma. Find more about it in the next video from Simplilearn and welcome back!
Time for Insights
The name "Six Sigma" comes from the statistical concept of standard deviation, where each sigma level represents a degree of process performance. The goal is to achieve a Six Sigma level, which means an extremely high level of quality with very few defects.
In Six Sigma, the sigma levels represent the quality and control of a process. At Sigma Level 1 (σ1), processes are poorly controlled, resulting in approximately 691,462 defects per million opportunities (DPMO). Sigma Level 2 (σ2) still has a high defect rate, around 308,537 DPMO. Sigma Level 3 (σ3) shows improvement but has room for enhancement at roughly 66,807 DPMO. Sigma Level 4 (σ4) represents reasonable quality with about 6,210 DPMO defects. Sigma Level 5 (σ5) indicates good process control, yielding about 233 DPMO defects. The ultimate goal, Sigma Level 6 (σ6), known as Six Sigma, signifies an exceptionally high level of quality with fewer than 3.4 defects per million opportunities (DPMO), demonstrating a commitment to top-tier performance and customer satisfaction.
To calculate DPMO (Defects Per Million Opportunities), you need to know the following information:
The total number of defects found in a process.
The total number of opportunities for defects to occur in that process. This involves analysing the process to identify all the potential points or opportunities where a defect could occur.
The formula for calculating DPMO is as follows:
We’ll discuss more about this concepts in later posts!
Good subject…. I was at Motorola in the 1980s and was in a corporate meeting when SIX SIGMA was first mentioned, and did a lot with it within my division at the time as the department head for manufacturing engineering...
A key point is that Motorola did not launch it to reduce process variability we already had SPC tools to do that… and they are now a part of what is now six sigma.
The real motivation for Six Sigma was to take the DFM journey we as manufacturing engineers had been on with the product designers to the next level. So almost ALL of the six sigma projects involved how to make new products and the associated processes more compatible and better.
So, I caution anyone trying to implement this tool on only the process as the real power is when you can also adjust the design specification goal posts with DFM tools linked into the project.
The other point is that you need to identify the waste using LEAN tools first so you don’t optimise waste when the goal should be to remove it. This is how I teach six sigma.