5.
Process Improvement
5.6. Case Studies 5.6.1. Eddy Current Probe Sensitivity Case Study


Model Provides Additional Insight 
Although deriving the fitted model was not the primary purpose
of the study, it does have two benefits in terms of additional
insight:


Global Prediction 
How does one predict the response at points other than those
used in the experiment? The prediction equation yields good
results at the eight combinations of coded 1 and +1 values for
the three factors:
Inserting these coded values into the fitted equation yields, as desired, a predicted value of


Global Determination of Best Settings  In order to determine the best settings for the factors, we can use a DOE contour plot. The DOE contour plot is generated for the two most significant factors and shows the value of the response variable at the vertices (i.e, the 1 and +1 settings for the factor variables) and indicates the direction that maximizes (or minimizes) the response variable. If you have more than two significant factors, you can generate a series of DOE contour plots with each one using two of the important factors.  
DOE Contour Plot 
The following is the DOE contour plot of the number of turns and the
winding distance.
The maximum value of the response variable (eddy current) corresponds to X1 (number of turns) equal to 1 and X2 (winding distance) equal to +1. The lower right corner of the contour plot corresponds to the direction that maximizes the response variable. This information can be used in planning the next phase of the experiment. 