6.2. Framing the Problem

In June 2008, a Six Sigma project team is assembled and charged with improving the yield of the anodizing process. Sean Cargill, a black belt for Components Inc., is assigned the task of leading the Six Sigma project.

Sean brings the team together and initiates the Define phase of the project. In conjunction with the project sponsor and the assembled team, Sean develops the initial project charter, shown in Exhibit 6.2. Note that the team identifies process yield as the Key Performance Indicator (KPI). The team realizes that if this process measure improves, so will delivery performance.

Figure 6.2. Project Charter

Sean and the team begin working on the project by constructing a process map for the anodizing process. To do this, they enlist the help of manufacturing personnel, which the team agrees is critical to success. Their map, shown in Exhibit 6.3, contains the basic process steps as well as key inputs (the boxes below each step) and outputs (the boxes above each arrow connecting the steps) at each step.

Figure 6.3. Process Map of the Anodizing Process

Sean then works with the team to define critical to quality (CTQ) output variables. The key measures of quality are the thickness of the anodize coating and the color of the parts. The anodize thickness is measured in thousandths of an inch using a backscatter radiation gauge. The color is qualitatively assessed by inspectors and measured quantitatively with a spectrophotometer. The spectrophotometer provides a color assessment based on the three-axis coordinate color scheme also known as the CIELAB (Commission Internationale de l'Eclairage) color space. Every color can be uniquely defined in a three-dimensional space using the attributes L*, a*, and b*. L* is a measure of lightness of the color (the range is 0–100 with lower values indicating darker color), a* is a measure of red/green (positive values indicate redness and negative values indicate greenness), and b* is a measure of yellow/blue (positive values indicate yellowness and negative values indicate blueness). Measurements are given in CIELAB units.

Thus, there are four continuous CTQs for the anodizing process: anodize coating thickness and the three color coordinates. Although the project charter identifies yield as the KPI, Sean and the team believe that these four continuous Y measurements determine yield. They realize that these measures will prove much more informative in the team's work than would the attribute-based percent yield measurement.