Capability Analysis in a Six Sigma Project

My team and I at Six SigmaSix Sigma Definition: Six Sigma is a set of techniques and t... Development Solutions, Inc. are engaged in LeanLEAN Definition LEAN is a production method aimed primarily ... and Six Sigma project work about 60% of the time. We encounter many different opportunities from a variety of disciplines. We are often called in to act as added capacity to an organization that has a continuos improvement system in place. When engaged with the teams at these organizations, I am often witness to a team “jumping into the deep weeds” of root cause analysis without understanding if the processConsists of input, value-add, and output. Learn More... is working as was originally engineered to work. If not, where is the delta.

I have an analogy that I like to use in class when teaching the concept of capability analysis. The analogy is called “Closing Open Windows” and is as follows: I drive up to my house open July day when it is 105 degrees Fahrenheit outside. I can hear my condenser (my A/C’s external unit) humming. I have an A/C unit that is rated for a house much larger than mine because I am not fond of the heat. When I enter my house, it is 98 degrees inside. Something is wrong. I check my thermostat and it reads 74 degrees. I check to make sure cold air is I being pushed out through my vents. The cold air is effectively being diffused throughout the house. What is the next thing that you would investigate? Most would answer that you would check for open doors and windows. That is the obvious answer, but I see “trained” practitioners first knocking holes in the walls to see if they are missing insulation. They are jumping into a deep root cause analysis without understanding the current state capability of the Inputs.

The reason that Six Sigma practitioners spend time meticulously defining the inputs into the process, in part is to understand what we can measure. Those inputs with variable measurements potentially have tolerances. Those tolerances once understood to be the true voice of the customer, will then help us to understand the capability of the current state of the process inputs. Once we understand both the Stability and Capability (through Capability Analysis) of each of the applicable inputs, this will help us to focus on those inputs with less capability. These inputs will potentially help us to understand the nature of the problem. All of this first depends on a trustworthy measurement system.

The principle of “Occam’s Razor” says that often the simplest answer is the right one. Understand how the process was engineered to operate. Find manuals, SOP’s, FMEA’s and/or any other documentation. Call the Manufacturer of the machine or cell. Understand what the measurable inputs are in the process and understand their current state capability. Look for “Open Windows” first.

Have you witnessed a team diving into a deep root cause analysis in a Six Sigma project without first looking for “open windows”?