Six Sigma DMAIC – Measure Stage
One of the most important elements of Six Sigma is that unlike many other quality management methodologies, it verifies improvement in terms of numbers. The use of measurement and statistics is a fundamental requirement of the process methodology.
In this second stage of DMAIC, a detailed process level map is developed for the current state of the process – the as-is process. This map works down on the elements defined in the high level map by adding decision points and showing options at each choice box of the process.
A process is a series of tasks that is repeated time and again. It has a set order to it, and the people who do it on a daily basis are best placed to tell you about it. Their view may differ from their supervisors. They may have created their own working customization’s to the process. It is often the case that the described process has some anomalies or differences in the practical real-world action.
In order to get a comprehensive and detailed process flow map, the personnel who do the daily process should be enlisted in creating it. It’s worth noting that human engagement within a process over time is likely to create the most variation within that process. The slight differences in output may be the result of differing personnel and their variety of customization. You will need to capture all these variations within the process flow.
Cause and effect diagrams are often referred to as Fishbone diagrams because of the nature of their shape. They are graphical representations of brainstorming and think-tank periods when looking at all the potential causes of underlying process factors investigated during the Analyze stage, or they generate potential failures to be addressed later on.
Begin by brainstorming all potential relationships. Next, state the outcomes in terms of problems or issues. Choose significant branches to form the main bones of examination. Follow the path along the bone to agree or dismiss potential causes – remembering that these are potentials and not known until validated.
Process analysis tools
- Analyze processes by developing and using value stream maps, process maps, flowcharts, procedures, work instructions, spaghetti diagrams, circle diagrams, etc.
Value stream maps show the “value stream” of a process and allow project teams to visualize processes. Value stream mapping is used to identify major sources of non value-added time in a value stream, envision a less wasteful future state, and develop an implementation plan for future activities. Flowcharts show the steps in a process from start to finish. Procedures are documents (instructions) that specify how a process is to be carried out. They may also indicate standard operating procedures.
Work instructions specify the steps that need to occur for tasks in a process. Spaghetti diagrams identify potential improvements to a physical layout to remove unnecessary movement or bottlenecks. Spaghetti diagrams are primarily used for Lean manufacturing in production facilities.
The equation y = f (x) in quality terms explains all of the following:
- The input x which results in the output y
- The framework for Ishikawa diagrams
- Process failure causes
- The sigma level