1. Why/When is Taguchi Method Appropriate?
A new tip Every Friday
Friday, 8th June 2001

2. Tip #8
Taguchi Method Finds best settings to optimize TWO quality characteristics Simultaneously (next 7 slides)
Friday, 8th June 2001

3. Taguchi Method : Finds best settings to optimize TWO quality characteristics Simultaneously
A process has “several” quality characteristics
Desirable Qualities
e.g. Larger-the-Better (strength, throughput etc)
or Nominal-the-Best (specified dimensions, uniformity)
Undesirable properties
e.g. Smaller-the-better (defects, resources - material/time, cost)
Objective of Taguchi Method is to determine the best settings of Control Factors such that
Desirable qualities are enhanced
.and.
Undesirable properties are minimized/eliminated
Process becomes ROBUST i.e. insensitive to NoIsE

4. Taguchi Method : Finds best settings to optimize TWO quality characteristics Simultaneously
Taguchi Method is most effective when there is at least one quality characteristic that is sensitive to variations or NoIsE
Desirable Qualities
e.g. “Nominal-the-Best” type are sensitive to NoIsE
S/N Ratio  = 10 Log10 ( mean2 / Variance )
Undesirable properties
e.g. “Smaller-the-better ” type are also sensitive to NoIsE
S/N Ratio  = – 10 Log10 ( 1/n  Yi2 )
 – 10 Log10 (Variance) if ideal value = zero

5. Taguchi Method : Finds best settings to optimize TWO quality characteristics Simultaneously
Let us use the “quality Loss” function for quality characteristics
Desirable Qualities
e.g. “Nominal-the-Best”
Quality Loss, Qa = (Variance / mean2 ) = ( 2 / 2 )
e.g. “Larger-the-Better”
Quality Loss, Qa = [ 1/n  (1/Yi2 ) ]
Undesirable properties
e.g. “Smaller-the-better ”
Quality Loss, Qa = [ 1/n  Yi2 ]

6. Taguchi Method : Finds best settings to optimize TWO quality characteristics Simultaneously
We can “minimize” the “Total quality Loss” function for TWO or more quality characteristics
Total Quality Loss, Qa,total = Qa,1 + Qa,
To obtain SN Ratio, take the Log-form of the “Total quality Loss” function
SN Ratio = -10 Log [ Qa,total ]
= -10 Log [ Qa,1 + Qa,2 + Qa, ]

7. Taguchi Method : Finds best settings to optimize TWO quality characteristics Simultaneously
We can “add” the “quality Loss” functions for TWO quality characteristics, as given below
Desirable Qualities
e.g. TWO quality characteristics of “Nominal-the-Best” type
Combined Quality Loss, Qa = ( 12 / 12 ) + ( 22 / 22 )
e.g. TWO quality characteristics of “Larger-the-Better” type
Combined Quality Loss, Qa = [1/m (1/Y1j ) 2] + [1/n (1/Y2j ) 2]
Undesirable properties
e.g. TWO quality characteristics of “smaller-the-better” type
Combined Quality Loss, Qa = [1/m (Y1j ) 2] + [1/n (Y2j ) 2]

8. Example : Computer Benchmarking
Taguchi Method : Finds best settings to optimize TWO quality characteristics Simultaneously
Example : Computer Benchmarking
Time required for obtaining the time and date  T1
Time required for opening and closing a file  T2
Desired quality characteristics :
time T1 and T2 both  “smaller-the-better”
Total Quality Loss, Qa,total = [1/m (T1j ) 2] + [1/n (T2j ) 2]
To obtain SN Ratio, take the Log-form of the “Total quality Loss”
SN Ratio = -10 Log [ {1/m (T1j ) 2} + {1/n (T2j ) 2} ]

9. Example : Telecom Connectivity
Taguchi Method : Finds best settings to optimize TWO quality characteristics Simultaneously
Example : Telecom Connectivity
Calls connected per hour on X’Mas day  C1
Calls connected per hour on Monday morning  C2
Desired quality characteristics :
calls C1 and C2 both  “Larger-the-Better”
Total Quality Loss, Qa,total = [1/m (1/C1j ) 2] + [1/n (1/C2j ) 2]
To obtain SN Ratio, take the Log-form of the “Total quality Loss”
SN Ratio = -10 Log [ {1/m (1/C1j ) 2} + {1/n (1/C2j ) 2} ]
Friday, 8th June 2001

10. Earlier Tips Links below
Friday, 27th July 2001
Friday, 20th July 2001
Friday, 13th July 2001
Taguchi Method
“inner” L9 array with “outer” L4 and L9 NoIsE arrays
“inner” L18 array with “outer” L4 and L9 NoIsE arrays
Taguchi Method Why/When is Taguchi Method not Appropriate?
Tips 12, 11, 10 

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

12. Earlier Tips Links below
Taguchi Method Identifies the “right” NoIsE factor(s) for Tolerance Design
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, 15th June 2001
Friday, 8th June 2001
Friday, 1st June 2001
Tips 6, 5, 4 

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

14. Earlier Tips Links below
Friday, 4th May 2001
Friday, 27th April 2001
Friday, 6th April 2001
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

15. end