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

5.6.1.3.

Interaction Effects

Check for Interaction Effects: DOE Interaction Plot

In addition to the main effects, it is also important to check for interaction effects, especially two-factor interaction effects. The DOE interaction effects plot is an effective tool for this. The effects on the plot represent the change in sensitivity from low to high levels of the factors.

Conclusions from the DOE Interaction Effects Plot

We can make the following conclusions from the DOE interaction effects plot.

1. Important Factors: Looking for the plots that have the steepest lines (that is, largest effects), we note that:
   • X1 (number of turns) is the most important effect: estimated effect = -3.1025;
   • X2 (winding distance) is next most important: estimated effect = -0.8675;
   • X3 (wire gauge) is relatively unimportant;
   • All three two-factor interactions are relatively unimporant.

2. Best Settings: As with the main effects plot, the best settings to maximize the sensitivity are
   (X1,X2,X3) = (+1,-1,+1)

   but with the X3 setting of +1 mattering little.