## Case Studies

#### A Balancing Act: Optimizing a Product's Properties

G.C. Derringer provides an easy-to-read explanation of the commonly used optimization function called desirability. When used as the final step in DOE, this function allows simultaneous optimization of multiple responses, resulting in the discovery of a group of optimal factor settings.

#### Optimizing Formulation Performance with Desirability Functions

Formulators often must make tradeoffs between conflicting performance measures. This paper illustrates how multiple response measures can be combined into one objective function, called "desirability", which can then be optimized by univariate techniques. The methodology consists of several basic steps: - Develop predictive models for each response - Transform each response to a desirability scale - Mathematically combine the individual desirability measures in to one overall index - Use numerical optimization methods to find the formulation that produces maximum overall desirability. By way of a case study on material used to make pipe, the paper shows how to generate models from statistically designed mixture experiments. Then by application of desirability functions, the optimum combinations of ingredients become apparent. Two and three dimensional surface maps, generated from commercially available personal computer software, will be illustrated.

#### Applying DOE to Microwave Popcorn

Process Industries (PI) Quality.

#### Optimizing Plasma Sprayed Alumina-Titania Coatings Using Statistical Methods

A statistical design of experiment study of the plasma spraying of alumina-titania powder is presented. In this study, the coating design has been optimized starting with classical experiments, progressing through fractional and full-factorial experiments, and concluding with response surface methodologies. The alumina-titania powder system in this study is being used in the fabrication of heater tubes that emulate nuclear fuel tubes for use in thermal-hydraulic testing. A substantial range of plasma processing conditions and their effect on the resultant coating are presented. The coatings were characterized by hardness tests, electrical tests, and optical metallography (i.e., image analysis). Coating qualities are discussed with respect to dielectric strength, hardness, porosity, surface roughness, deposition efficiency, and microstructure. Attributes of the coatings are correlated with the changes in operating parameters. An optimized coating design is presented for this specific application.

#### Analyzing Two-Level Factorials Having Missing Data

Analyzing Two-Level Factorials Having Missing Data, an abstract of a paper given at the 37th Annual Fall Technical Conference

#### A Simple Comparative Experiment with Paper Clips

Stat-Ease, Inc. uses millions of paper clips per year. The vice-president in charge of office supplies believes that big clips, although initially more costly, would save money over the long run due to their strength.

#### The Role of Pure Error on Normal Probability Plots

A look at augmenting the usual probability plot effects with points representing pure error.

#### DOE It Yourself

Fun science projects.

#### Experiments Uncover Source of Valve Failures

Company engineers at Fluoroware Ind. chose to use Design-Expert software to troubleshoot customer complaints that their plastic components were failing prematurely. In the past, doing this sort of test could be very complicated; however, using DOE to test multiple factors at once significantly simplified the process.

#### How to Document Process Monitoring and Control Systems

Maximize plant capability and efficiency by developing specifications for all aspects of a process.