Design of Experiments (DOE) Using the Taguchi Approach
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Design of Experiments (DOE) Using the Taguchi Approach This document contains brief reviews of several topics in the technique. For summaries of the recommended steps in application, read the published article attached. (Available for free download and review.) TOPICS: • Subject Overview • References Taguchi Method Review • Application Procedure • Quality Characteristics Brainstorming • Factors and Levels • Interaction Between Factors Noise Factors and Outer Arrays • Scope and Size of Experiments • Order of Running Experiments Repetitions and Replications • Available Orthogonal Arrays • Triangular Table and Linear Graphs Upgrading Columns • Dummy Treatments • Results of Multiple Criteria S/N Ratios for Static and Dynamic Systems • Why Taguchi Approach and Taguchi vs. Classical DOE • Loss Function • General Notes and Comments Helpful Tips on Applications • Quality Digest Article • Experiment Design Solutions • Common Orthogonal Arrays Other References: 1. DOE Demystified.. : http://manufacturingcenter.com/tooling/archives/1202/1202qmdesign.asp 2. 16 Steps to Product... http://www.qualitydigest.com/june01/html/sixteen.html 3. Read an independent review of Qualitek-4: http://www.qualitydigest.com/jan99/html/body_software.html 4. A Strategy for Simultaneous Evaluation of Multiple Objectives, A journal of the Reliability Analysis Center, 2004, Second quarter, Pages 14 - 18. http://rac.alionscience.com/pdf/2Q2004.pdf 5. Design of Experiments Using the Taguchi Approach : 16 Steps to Product and Process Improvement by Ranjit K. Roy Hardcover - 600 pages Bk&Cd-Rom edition (January 2001) John Wiley & Sons; ISBN: 0471361011 6. Primer on the Taguchi Method - Ranjit Roy (ISBN:087263468X Originally published in 1989 by Van Nostrand Reinhold. Current publisher/source is Society of Manufacturing Engineers). The book is available directly from the publisher, Society of Manufacturing Engineers (SME ) P.O. Box 6028, Dearborn, Michigan 48121, USA.256 Pages. 50 Illustrations. Order code: 2436-2487. For open enrollment seminar on Taguchi DOE technique, visit http://Nutek-us.com/wp-s4d.html . www.Nutek-us.com Subject Overview (The Taguchi Approach) - How much money you can save the design Design Of Experiments (DOE) is a powerful statistical - How you can determine which factor is technique introduced by R. A. Fisher in England in causing most variations in the result the 1920's to study the effect of multiple variables - How you can set up your process such that it simultaneously. In his early applications, Fisher is insensitive to the uncontrollable factors wanted to find out how much rain, water, fertilizer, - Which factors have more influence on the sunshine, etc. are needed to produce the best crop. mean performance Since that time, much development of the technique What you need to do to reduce performance has taken place in the academic environment, but did - variation around the target help generate many applications in the production floor. - How your response varies proportional to signal factor (Dynamic response) As a researcher in Electronic Control Laboratory in - How to combine multiple criteria of Japan, Dr. Genechi Taguchi carried out significant evaluation into a single index research with DOE techniques in the late 1940's. He - How you can adjust factor for overall spent considerable effort to make this experimental satisfaction of criteria an adjust factors for a technique more user-friendly (easy to apply) and system whose of evaluations applied it to improve the quality of manufactured - How the uncontrollable factors affect the products. Dr. Taguchi's standardized version of DOE, performance popularly known as the Taguchi method or Taguchi etc., approach, was introduced in the USA in the early 1980's. Today it is one of the most effective quality building tools used by engineers in all types of Advantage of DOE Using Taguchi Approach manufacturing activities. The application of DOE requires careful planning, The DOE using Taguchi approach can economically prudent layout of the experiment, and expert analysis satisfy the needs of problem solving and of results. Based on years of research and product/process design optimization projects. By applications Dr. Genechi Taguchi has standardized learning and applying this technique, engineers, the methods for each of these DOE application steps scientists, and researchers can significantly reduce described below. Thus, DOE using theTaguchi the time required for experimental investigations. approach has become a much more attractive tool to practicing engineers and scientists. DOE can be highly effective when yow wish to: - Optimize product and process designs, study Experiment planning and problem formulation - the effects of multiple factors (i.e.- variables, Experiment planning guidelines are consistent with parameters, ingredients, etc.) on the modern work disciplines of working as teams. performance, and solve production problems Consensus decisions about experimental objectives by objectively laying out the investigative and factors make the projects more successful. experiments. (Overall application goals). - Study Influence of individual factors on the Experiment layout -High emphasis is put on cost and performance and determine which factor has size of experiments... Size of the experiment for a more influence, which ones have less. You given number of factors and levels is standardized... can also find out which factor should have Approach and priority for column assignments are tighter tolerance and which tolerance should established... Clear guidelines are available to deal be relaxed. The information from the with factors and interactions (interaction tables)... experiment will tell you how to allocate Uncontrollable factors are formally treated to reduce quality assurance resources based on the variation... Discrete prescriptions for setting up test objective data. It will indicate whether a conditions under uncontrollable factors are supplier's part causes problems or not described... Guidelines for carrying out the (ANOVA data), and how to combine different experiments and number of samples to be tested are factors in their proper settings to get the best defined results (Specific Objectives). Data analysis -Steps for analysis are standardized (main effect, NOVA and Optimum)... Standard Further, the experimental data will allow you practice for determination of the optimum is determine: recommended... Guidelines for test of significance - How to substitute a less expensive part to get the and pooling are defined... same performanceNutek, Inc. Bloomfieldimprovement Hills, MI.you USA. propose Tel: 1-248-540-4827 [email protected] www.Nutek-us.com 0607 Page 2 APPROACH: ROBUST DESIGN Interpretation of results - Clear guidelines about meaning of error term... Discrete indicator about - Reduce variation without actually removing the cause of variation. Achieve consistent confirmation of results (Confidence interval)... Ability to quantify improvements in terms of dollars (Loss performance by making product/process insensitive to the influence of uncontrollable factors. function) Overall advantage - DOE using Taguchi approach attempts to improve quality which is defined as the WHAT DOES IT DO? - Optimize design, solve consistency of performance. Consistency is achieved problems, build robust products, etc. when variation is reduced. This can be done by moving the mean performance to the target as well WHAT DOES IT DO? as by reducing variations around the target. The - Optimize design, solve problems, build robust prime motivation behind the Taguchi experiment products, etc. design technique is to achieve reduced variation (also known as ROBUST DESIGN). This technique, WHY DO IT? therefore, is focused to attain the desired quality - Save cost (Reduce warranty, rejection and objectives in all steps. The classical DOE does not cost of development). specifically address quality . AREAS OF APPLICATION: "The primary problem addressed in classical - Analytical simulation (in early stages of statistical experiment design is to model the design). response of a product or process as a function of - Development testing (in design and many factors called model factors. Factors, called development). nuisance factors, which are not included in the - Process development. model, can also influence the response... The - Manufacturing. primary problem addressed in Robust Design is how - Problem solving in all areas of manufacturing to reduce the variance of a product's function in the and production. customer's environment." -Madhav Phadke, Quality Engineering using Robust Design. WHAT'S NEW? 1. NEW PHILOSOPHY - Building quality in the product design. - Measuring quality by deviation from target (not by rejection). 2. NEW DISCIPLINE - Complete planning of experiments and evaluation criteria before conducting experiments. - Determining a factor's influence by running the complete experiment. 3. SIMPLER AND STANDARDIZED EXPERIMENT DESIGN FORMAT - Orthogonal arrays for experimental design. - Outer array design for robust product design. - More clear and easier methods for analysis of results. QUALITY: DEFINITION and OBJECTIVE http://nutek-us.com/wp-txt.html - Reduced variation around the target with least cost. Nutek, Inc. Bloomfield Hills, MI. USA. Tel: 1-248-540-4827 [email protected] www.Nutek-us.com 0607 Page 3 TAGUCHI METHOD REVIEW BRAINSTORMING SUGGESTED TOPICS OF DISCUSSIONS: APPLICATION STEPS The Taguchi method is used to improve the 1. OBJECTIVES AND EVALUATION CRITERIA quality