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

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

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

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

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 ]

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,2 + . . . 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,3 + . . . ]

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]

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} ]

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

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 

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 

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 

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 

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

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