Steps for conducting a Taguchi designed experiment

Before you start using Minitab, you need to choose control factors for the inner array and noise factors for the outer array. Control factors are factors you can control to optimize the process. Noise factors are factors that can affect the performance of a system but are not in control during the intended use of the product.

While you cannot control noise factors during the process or product use, you need to be able to control noise factors for experimentation purposes.

Engineering knowledge should guide the selection of control factors and responses. You should also scale control factors and responses so that interactions are unlikely. When interactions between control factors are likely or not well understood, you should choose a design that is capable of estimating those interactions. Minitab can help you design a Taguchi experiment that does not confound interactions of interest with each other or with main effects.

Noise factors for the outer array should also be carefully selected and might require preliminary experimentation. The noise levels selected should represent the range of conditions under which the response variable should remain robust.

Conducting a Taguchi designed experiment can have the following steps:

  1. Choose Stat > DOE > Taguchi > Create Taguchi Design to generate a Taguchi design (orthogonal array). Each column in the orthogonal array represents a specific factor with two or more levels. Each row represents a run; the cell values identify the factor settings for the run. By default, Minitab's orthogonal array designs use the integers 1, 2, 3, to represent factor levels. If you enter factor levels, the integers 1, 2, 3, will be the coded levels for the design. You can also use Stat > DOE > Taguchi > Define Custom Taguchi Design to create a design from data that you already have in the worksheet. Define Custom Taguchi Design lets you specify which columns are your factors and signal factors. You can then easily analyze the design and generate plots.
  2. After you create the design, you can display or modify the design:
    • Choose Stat > DOE > Display Design to change the units (coded or uncoded) in which Minitab expresses the factors in the worksheet.
    • Choose Stat > DOE > Modify Design to rename the factors, change the factor levels, add a signal factor to a static design, ignore an existing signal factor (treat the design as static), and add new levels to an existing signal factor.
  3. Conduct the experiment and collect the response data. The experiment is done by running the complete set of noise factor settings at each combination of control factor settings (at each run). The response data from each run of the noise factors in the outer array are usually aligned in a row, beside the factor settings for that run of the control factors in the inner array.
  4. Choose Stat > DOE > Taguchi > Analyze Taguchi Design to analyze the experimental data.

    You should analyze each response variable separately with Taguchi designs. Although Taguchi analysis accepts multiple response columns, these responses should be the same variable measured under different noise factor conditions.

  5. Choose Stat > DOE > Taguchi > Predict Taguchi Results to predict signal to noise ratios and response characteristics for selected new factor settings.
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