2. Why/When is Taguchi Method Appropriate? Friday, 18 th May 2001 Tip #5 Taguchi Method Appropriate Signal-to-Noise Ratio Appropriate Signal-to-Noise Ratio for Quality Characteristics approaching IDEAL value

3. Taguchi Method Appropriate Signal-to-Noise Ratio for Quality Characteristics approaching IDEAL value (next 7 slides) Friday, 18 th May 2001 Tip #5

4. Taguchi’s SN Ratio Quality Characteristics approaching IDEAL value smaller-the-betterTaguchi’s SN-Ratio for smaller-the-better –quality characteristics is usually an undesired output, for example Defects like pin holes, particulates in deposition processes Unwanted by-product or side effect LARGER-THE-BETTERTaguchi’s SN-Ratio for LARGER-THE-BETTER –quality characteristics is usually a desired output, for example Bond strength Critical Current NOMINAL-the-bestTaguchi’s SN-Ratio for NOMINAL-the-best –quality characteristics is usually a nominal output, for example most parts in mechanical fittings have nominal dimensions Ratios of chemicals or mixtures are nominally the best type. Thickness should be uniform in deposition /growth /plating /etching..

5. But what about quality characteristics that approachBut what about quality characteristics that approach an ideal value? –Examples are Efficiency : all efficiencies approach the ideal value of 100% Weld strength : approaches the ideal strength of the material Critical temperature or Critical current density for High Temperature superconductors (YBCO) : These approach ideal values, say 92K and 10 8 A/cm 2 Which SN-Ratio is most suitable among the following ?Which SN-Ratio is most suitable among the following ? –smaller-the-better –LARGER-THE-BETTER –NOMINAL-the-BEST Taguchi’s SN Ratio Quality Characteristics approaching IDEAL value

6. smaller-the-betterTaguchi’s SN-Ratio for smaller-the-better Defects ( quality characteristics is usually an undesired output, say Defects ) –S/N Ratio  = – 10 Log 10 ( 1/n  Y i 2 ) LARGER-THE-BETTERTaguchi’s SN-Ratio for LARGER-THE-BETTER Current ( quality characteristics is usually a desired output, say Current ) –S/N Ratio  = – 10 Log 10 ( 1/n  1/ Y i 2 ) Taguchi’s SN-Ratio for NOMINAL-the-best Diameter ( quality characteristics is usually a nominal output, say Diameter ) –S/N Ratio  = 10 Log 10 (  2 /  2 ) Taguchi’s SN Ratio Quality Characteristics approaching IDEAL value

7. Generally, we would state that this value should be “LARGER-THE-BETTER” However, there exists an IDEAL value!!! QUESTION still IS “Which SN-Ratio is most suitable among the following ?” –LARGER-THE-BETTER –smaller-the-better –Nominal-the-best Taguchi’s SN Ratio Quality Characteristics approaching IDEAL value

8. Reword the SN-Ratio for smaller-the-better to indicate ‘the approach to IDEAL value’ by saying “Smaller-the-difference-from-IDEAL-the-better” smaller-the-bettermodifiedTaguchi’s SN-Ratio for smaller-the-better is now modified ( for quality characteristics approaching IDEAL output ) –S/N Ratio  = – 10 Log 10 [ 1/n  (Y IDEAL - Y i ) 2 ] Taguchi’s SN Ratio Quality Characteristics approaching IDEAL value

9. IDEAL valueIf our nominal values are far away from IDEAL value –SN-Ratio for LARGER-THE-BETTER will give good additivity (prediction and results will match well) If our nominal values are already close to IDEAL value –SN-Ratio for smaller-the-better (the modified form) will give good additivity (prediction and results will match well)  = – 10 Log 10 [ 1/n  (Y IDEAL - Y i ) 2 ] Taguchi’s SN Ratio Quality Characteristics approaching IDEAL value

10. SN-Ratio for LARGER-THE-BETTER tends to predict optimistic (LARGER) values –Sometimes the value exceeds maximum possible value !? SN-Ratio for smaller-the-better (the modified form) always predicts values pessimistically (LESS than ideal value) TRY BOTH, Select one with less ANOVA error TRY BOTH, Select one with less ANOVA error Taguchi’s SN Ratio Quality Characteristics approaching IDEAL value Friday, 18 th May 2001

11. More Tips Links below 16.Taguchi Method V a r i a n c e R e d u c t i o n Factor Effects 1 st Priority : V a r i a n c e R e d u c t i o n 2 nd Priority : Factor Effects “inner” “outer” 15. “inner” L9 array with “outer” L4 and L9 NoIsE arrays 14.Taguchi Method “inner” “outer” “inner” L18 array with “outer” L4 and L9 NoIsE arrays not 13.Taguchi Method Why/When is Taguchi Method not Appropriate? Friday, 3rd Aug 2001 Friday, 27 th July 2001 Friday, 20 th July 2001 Friday, 13 th July 2001 Tips 12, 11, 10 

12. More Tips Links below 12.Taguchi Method “inner” “outer” “inner” L8 array with “outer” L4 and L9 NoIsE arrays 11.Taguchi Method ALL Life-stages Useful at ALL Life-stages of a Process or Product 10.Taguchi Method “centering”“fine tuning” Performs Process “centering” or “fine tuning” Friday, 6 th July 2001 Friday, 29 th June 2001 Friday, 22 nd June 2001 Tips 9, 8, 7 

13. More Tips Links below NoIsE Tolerance Design 9.Taguchi Method Identifies the “right” NoIsE factor(s) for Tolerance Design 8.Taguchi Method Finds best settings to optimize TWO quality characteristics Simultaneously 7. Taguchi Method When to select a ‘Larger’ OA to perform “Factorial Experiments” Friday, 15 th June 2001 Friday, 8 th June 2001 Friday, 1 st June 2001 Tips 6, 5, 4 

14. More Tips Links below 6.Taguchi Method Using Orthogonal Arrays for Generating Balanced Combinations of NoIsE Factors approaching IDEAL value 5.Taguchi Method Signal-to-Noise Ratio for Quality Characteristics approaching IDEAL value 4. Taguchi Method improves " quality “ at all the life stages the design stage itself at the design stage itself Friday, 25 th May 2001 Friday, 18 th May 2001 Friday, 11 th May 2001 Tips 3, 2, 1 

15. More Tips Links below Concurrent Engineering 3.Taguchi Method Appropriate for Concurrent Engineering 2.Taguchi Method can study Interaction Noise Factors Control Factors between Noise Factors and Control Factors Signal-to-Noise Ratios Log form 1.Taguchi’s Signal-to-Noise Ratios are in Log form Friday, 4 th May 2001 Friday, 27 th April 2001 Friday, 6 th April 2001

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