DMAIC Measure Phase
The M in DMAIC is about understanding the current process, how the process is measured, and it’s baseline (historical or pre-Six Sigma) performance.
Flow Chart the process
Flow-charting the process helps in three areas –
1. Not all team members are familiar with the entire process at the start of the project. Developing a process flowchart in a group session gives all team members a full appreciation for the inputs, outputs, controls, and value-added operations.
2. A good flowchart helps structure the Analyze phase, as team members consider possible sources of variation. It’s easy to overlook major causes of variation, and a complete process flowchart will help minimize this risk.
3. During the Control phase the team must decide on process controls and mistake proofing measures for long term control. Having a flowchart makes this process easier, especially as the team tries to work as far “upstream” as possible when implementing process controls.
Validate the Measurement System
We’ve participated in several projects where measurement system variation accounted for most of the variation in the CTQ (critical-to-quality feature). One particular project actually ended at the measurement phase, because the sigma level for the process improved drastically after the measurement system was fixed.
For manufacturing processes, it’s important to run a full Gage Repeatability and Reproducibility (Gage R & R) study on the measurement system prior to validating baseline data and proceeding with the project. The GR&R contribution to variation should be no more than 20% of the CTQ tolerance.
For business metrics like customer satisfaction, the team should understand how the data is collected and converted into the CTQ metric. Discussion should also take place with key stakeholders in the business to ensure that the CTQ best reflects what is important to the customer.
Determine Baseline Sigma Level
Enough data should be collected to understand the current sigma-level (i.e. 2.8, 3.4) . In some cases historical data is readily available, and in some cases the team must set up a process for collecting baseline data. If historical data is not available, we recommend that the team proceed with the Analyze phase of the project while collecting the baseline data need to complete the Measurement phase.