11.2 Uses of DoE
Experimental design can be used at the point of greatest leverage to reduce design costs by speeding up the design process, reducing late engineering design changes, and reducing product material and labor complexity. Designed Experiments are also powerful tools to achieve manufacturing cost savings by minimizing process variation and reducing rework, scrap, and the need for inspection.7
Designed experiments have many potential uses in improving processes and products, including:
Comparing Alternatives. In the case of our cake-baking example, we might want to compare the results from two different types of flour. If it turned out that the flour from different vendors was not significant, we could select the lowest-cost vendor. If flour were significant, then we would select the best flour. The experiment(s) should allow us to make an informed decision that evaluates both quality and cost.
Identifying the Significant Inputs (Factors) Affecting an Output (Response) - separating the vital few from the trivial many. We might ask a question: “What are the significant factors beyond flour, eggs, sugar and baking?”
Achieving an Optimal Process Output (Response). "What are the necessary factors, and what are the levels of those factors, to achieve the exact taste and consistency of Mom’s chocolate cake?
Reducing Variability. “Can the recipe be changed so it is more likely to always come out the same?”
Minimizing, Maximizing, or Targeting an Output (Response). “How can the cake be made as moist as possible without disintegrating?”
Improving process or product “Robustness” - fitness for use under varying conditions. “Can the factors and their levels (recipe) be modified so the cake will come out nearly the same no matter what type of oven is used?”
Balancing Tradeoffs when there are multiple Critical to Quality Characteristics that require optimization. “How do you produce the best tasting cake with the simplest recipe (least number of ingredients) and shortest baking time?”
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