why/when is taguchi method appropriate? friday, 18 th may 2001 tip #5 taguchi method appropriate...

Why/When is Taguchi Method Appropriate?

Friday, 18Friday, 18thth May 2001 May 2001

Tip #5Tip #5Taguchi Method

AppropriateAppropriate Signal-to-Noise RatioSignal-to-Noise Ratio for Quality Characteristics approaching IDEAL valueQuality Characteristics approaching IDEAL value

Taguchi Method Appropriate Signal-to-Noise Ratio

for Quality Characteristics

approaching IDEAL value (next 7 slides)

Friday, 18th May 2001

Tip #5Tip #5

Taguchi’s SN Ratio Quality Characteristics approaching IDEAL value

• Taguchi’s SN-Ratio for smaller-the-bettersmaller-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

• Taguchi’s SN-Ratio for LARGER-THE-BETTERLARGER-THE-BETTER

– quality characteristics is usually a desired output, for example

• Bond strength

• Critical Current

• Taguchi’s SN-Ratio for NOMINAL-the-bestNOMINAL-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..

• But what about quality characteristics that approach But what about quality characteristics that approach

an ideal value?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 108 A/cm2

• Which SN-Ratio is most suitable among the following ?Which SN-Ratio is most suitable among the following ?

– smaller-the-bettersmaller-the-better

– LARGER-THE-BETTERLARGER-THE-BETTER

– NOMINAL-the-BEST NOMINAL-the-BEST


• Taguchi’s SN-Ratio for smaller-the-bettersmaller-the-better

( quality characteristics is usually an undesired output, say Defects Defects )

– S/N Ratio = – 10 Log10 ( 1/n Yi2 )

• Taguchi’s SN-Ratio for LARGER-THE-BETTERLARGER-THE-BETTER

( quality characteristics is usually a desired output, say Current Current )

– S/N Ratio = – 10 Log10 ( 1/n 1/Yi2 )

• Taguchi’s SN-Ratio for NOMINAL-the-best

( quality characteristics is usually a nominal output, say Diameter Diameter )– S/N Ratio = 10 Log10 (

2 / 2 )


• 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 ?”Which SN-Ratio is most suitable among the following ?”– LARGER-THE-BETTER– smaller-the-better– Nominal-the-best


• Reword the SN-Ratio for smaller-the-better to indicate ‘the approach to IDEAL value’

by saying

““Smaller-Smaller-the-difference-from-IDEAL-the-difference-from-IDEAL-the-better”the-better”

• Taguchi’s SN-Ratio for smaller-the-bettersmaller-the-better is now modifiedmodified

( for quality characteristics approaching IDEAL output )

– S/N Ratio = – 10 Log10 [ 1/n (YIDEAL- Yi ) 2 ]


• If our nominal values are far away from IDEAL valueIDEAL 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 Log10 [ 1/n (YIDEAL- Yi ) 2 ]


• 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, TRY BOTH, Select one with less ANOVA error Select one with less ANOVA error



More Tips More Tips Links belowLinks below

16. Taguchi Method

1st Priority : VVaarriiaanncce e RReedduuccttiioonn

2nd Priority : Factor EffectsFactor Effects

15. “inner”“inner” L9 array with “outer”“outer” L4 and L9 NoIsE arrays

14. Taguchi Method

““inner”inner” L18 array with “outer”“outer” L4 and L9 NoIsE arrays

13. Taguchi Method

Why/When is Taguchi Method not not Appropriate?

Friday, 3rd Aug 2001

Friday, 27th July 2001



Tips 12, 11, 10 Tips 12, 11, 10


12. Taguchi Method

““inner”inner” L8 array with

“outer”“outer” L4 and L9 NoIsE arrays

11. Taguchi Method

Useful at ALL Life-stagesALL Life-stages of a Process or Product

10. Taguchi MethodPerforms Process “centering”“centering” or “fine tuning”“fine tuning”


Friday, 29th June 2001

Friday, 22nd June 2001

Tips 9, 8, 7 Tips 9, 8, 7


9. Taguchi Method

Identifies the “right” NNooIIssEE factor(s)

for Tolerance DesignTolerance Design

10. 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, 1st June 2001

Tips 6, 5, 4 Tips 6, 5, 4


6. Taguchi Method Using Orthogonal Arrays for Generating Balanced Combinations of NoIsE Factors

5. Taguchi Method Signal-to-Noise Ratio for Quality Characteristics

approaching IDEAL valueapproaching IDEAL value

4. Taguchi Method improves " quality “ at all the life stages

at the design stage itselfthe design stage itself




Tips 3, 2, 1 Tips 3, 2, 1


3. Taguchi Method Appropriate for Concurrent EngineeringConcurrent Engineering

2. Taguchi Method can study Interaction

between Noise Factors Noise Factors and Control Control FactorsFactors

1. Taguchi’s Signal-to-Noise RatiosSignal-to-Noise Ratios are in

Log formLog form


Friday, 27th April 2001

Friday, 6th April 2001

why/when is taguchi method appropriate? friday, 18 th may 2001 tip #5 taguchi method appropriate...

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