Why/When is Taguchi Method Appropriate?

1
Why/When is Taguchi Method Appropriate?

• A new tip Every Friday

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

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 )
• Desirable Qualities
• 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
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
Taguchi Method Finds best settings to optimize
TWO quality characteristics Simultaneously

• Example Telecom Connectivity
• Calls connected per hour on XMas 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

• 7. Taguchi Method
• When to select a Larger OA to perform
  Factorial Experiments
• Taguchi Method Using Orthogonal Arrays for
  Generating Balanced Combinations of NoIsE Factors
• 5. Taguchi Method Signal-to-Noise Ratio for
  Quality Characteristics approaching IDEAL value

• Friday, 1st June 2001
• Friday, 25th May 2001
• Friday, 18th May 2001

Tips 4,3,2,1 ?
11
Earlier Tips Links below

• Friday, 11th May 2001
• Friday, 4th May 2001
• Friday, 27th April 2001
• Friday, 6th April 2001

• 4. Taguchi Method improves " quality at all
  the life stages
• at the design stage itself
• 3. Taguchi Method Appropriate for Concurrent
  Engineering
• 2. Taguchi Method can study Interaction
• between Noise Factors and Control
  Factors
• 1. Taguchis Signal-to-Noise Ratios are in Log
  form

12
More Tips Links below

• Friday, 3rd Aug 2001
• Friday, 27th July 2001
• Friday, 20th July 2001
• Friday, 13th July 2001

• Taguchi Method
• 1st Priority Variance Reduction 2nd Priority
  Factor Effects
• 15. inner L9 array with outer L4 and L9
  NoIsE arrays
• Taguchi Method
• inner L18 array with outer L4 and L9 NoIsE
  arrays
• Taguchi Method Why/When is Taguchi Method not
  Appropriate?

Tips 12, 11, 10 ?
13
More 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
• Taguchi Method
• Useful at ALL Life-stages of a Process or
  Product
• Taguchi Method
• Performs Process centering or fine tuning

Tips 9, 8, 7 ?
14
More 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 ?
15
More 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 ?
16
More 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. Taguchis Signal-to-Noise Ratios are in Log
  form

17
end