ch01 - Chapter 1 Supplemental Text Material S-1.1 More...

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Chapter 1 Supplemental Text Material S-1.1 More About Planning Experiments Coleman and Montgomery (1993) present a discussion of methodology and some guide sheets useful in the pre-experimental planning phases of designing and conducting an industrial experiment. The guide sheets are particularly appropriate for complex, high- payoff or high-consequence experiments involving (possibly) many factors or other issues that need careful consideration and (possibly) many responses. They are most likely to be useful in the earliest stages of experimentation with a process or system. Coleman and Montgomery suggest that the guide sheets work most effectively when they are filled out by a team of experimenters, including engineers and scientists with specialized process knowledge, operators and technicians, managers and (if available) individuals with specialized training and experience in designing experiments. The sheets are intended to encourage discussion and resolution of technical and logistical issues before the experiment is actually conducted. Coleman and Montgomery give an example involving manufacturing impellers on a CNC-machine that are used in a jet turbine engine. To achieve the desired performance objectives, it is necessary to produce parts with blade profiles that closely match the engineering specifications. The objective of the experiment was to study the effect of different tool vendors and machine set-up parameters on the dimensional variability of the parts produced by the CNC-machines. The master guide sheet is shown in Table 1 below. It contains information useful in filling out the individual sheets for a particular experiment. Writing the objective of the experiment is usually harder than it appears. Objectives should be unbiased, specific, measurable and of practical consequence. To be unbiased, the experimenters must encourage participation by knowledgeable and interested people with diverse perspectives. It is all too easy to design a very narrow experiment to “prove” a pet theory. To be specific and measurable the objectives should be detailed enough and stated so that it is clear when they have been met. To be of practical consequence, there should be something that will be done differently as a result of the experiment, such as a new set of operating conditions for the process, a new material source, or perhaps a new experiment will be conducted. All interested parties should agree that the proper objectives have been set. The relevant background should contain information from previous experiments, if any, observational data that may have been collected routinely by process operating personnel, field quality or reliability data, knowledge based on physical laws or theories, and expert opinion. This information helps quantify what new knowledge could be gained by the present experiment and motivates discussion by all team members. Table 2 shows the beginning of the guide sheet for the CNC-machining experiment. Response variables come to mind easily for most experimenters.
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ch01 - Chapter 1 Supplemental Text Material S-1.1 More...

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