why taguchi method tip 5

8/10/2019 Why Taguchi Method Tip 5

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Why/When is Taguchi Method Appropriate?

Friday, 18th May 2001

Tip #5Taguchi Method

Appropriate Signal-to-Noise Ratio for

Quality Characteristics approaching IDEAL value



Taguchi MethodAppropriate Signal-to-Noise Ratio

forQuality Characteristics

approaching IDEAL value

(next 7 sl ides)


Tip #5



Taguchi’s SN Ratio Quality Characteristics approaching IDEAL value

• Taguchi’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

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

– quality characteristics is usually a desired output, for example

• Bond strength

• Critical Current

• Taguchi’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..



• But 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 108 A/cm2

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

– smaller-the-better

– LARGER-THE-BETTER

– NOMINAL-the-BEST




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

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

– S/N Ratio = – 10 Log10 ( 1/n Yi2 )

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

( quality characteristics is usually a desired output, say 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 )

– S/N Ratio = 10 Log10 ( 2 / 2

)




• Reword the SN-Ratio for smaller-the-better to

indicate „the approach to IDEAL value‟

by saying

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

• Taguchi’s SN-Ratio for smaller-the-better is now modified( 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 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, Select one with less ANOVA error


Friday, 18th

May 2001



More Tips Links below

16. Taguchi Method

1st Priority : Va r iance R eduction

2nd Priority : Factor Effects

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

14. Taguchi Method

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

13. Taguchi Method

Why/When is Taguchi Method not Appropriate?

Friday, 3rd Aug 2001

Friday, 27th July 2001



Tips 12, 11, 10

http://www.ee.iitb.ac.in/~apte/Why/WhyTaguchiMethodTip16.ppt


























12. Taguchi Method

“inner” L8 array with

“outer” L4 and L9 NoIsE arrays

11. Taguchi Method

Useful at ALL Life-stages of a Process or

Product

10. Taguchi Method

Performs Process “centering” or “fine tuning”


Friday, 29th June 2001

Friday, 22nd June 2001

Tips 9, 8, 7

























9. Taguchi Method

Identifies the “right” NoIsE factor(s)for Tolerance Design

8. Taguchi Method

F inds best settings to optimize

TWO quali ty character isticsSimultaneously

7. Taguchi MethodWhen to select a „Larger‟ OA to perform

“Factorial Experiments”



Friday, 1st June 2001

Tips 6, 5, 4

























6. Taguchi Method Using Orthog onal Arrays fo r Generat ing

Balanced Com binat ions o f NoIsE Factors

5. Taguchi Method Signal-to-Noise Rat io for Qual i ty

Character ist ics

approaching IDEAL value

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

at the design stage itself




Tips 3, 2, 1

























3. Taguchi Method Appropriate for Concurrent Engineering

2. Taguchi Method can study Interaction

between Noise Factors and Control

Factors

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

Log form


Friday, 27th April 2001

Friday, 6th

April 2001
























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why taguchi method tip 5

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