Taguchi Method

Taguchi Method

Taguchi methods are statistical methods, sometimes called robust design methods, developed by Genichi Taguchi to improve the quality of manufactured goods, and more recently also applied to engineering,biotechnology,marketing and advertising. The Taguchi method is an alternative method to review loss due to poor quality.
The Taguchi method of quality control is an approach to engineering that emphasizes the roles of research and development (R&D), product design and development in reducing the occurrence of defects and failures in manufactured goods.

Taguchi defines Quality as “The loss imparted by the product to society from the time the product is shipped.” 

LOSS = Cost to operate, Failure to function, maintenance and repair cost, customer satisfaction, poor design. 

Taguchi’s Vs Traditional Approach

Taguchi’s
Traditional
When a product moves from its Target will cause the loss even if the product lies or not within Limits.
There is Good or Bad Products only as per Limits.

Taguchi’s Quadratic Quality Loss Function

1. Quality Loss Occurs when a product’s deviates from target or nominal value.
2. Deviation Grows, then Loss increases.
3. Taguchi’s U-shaped loss Function Curve.


Formula to find Taguchi’s Loss Function 

Taguchi uses Quadratic Equation to determine loss Curve

L (x) = k (x-N)² 

Where L (x) = Loss Function, 
k = C/d² = Constant of proportionality
where C – Loss associated with specification limit 
d - Deviation of specification from target value 
x = Quality Features of selected product
N = Nominal Value of the product
(x-N) = Tolerance

Problem 1- A part dimension on a power tool is specified as 32.25±0.25.Company records show±0.25 exceeded & 75% of the returned fo replacement. Cost of replacement is Rs.12,500.Determine k & QLF.

Solution : Expected Cost of repair C = 0.75(12500) = Rs 9,375 
k = C/d²= 9375/(90.25)² = Rs 1,50,000 
QLF =L (x) 1,50,00(x-N)


Problem-2 If the specifications are 10±2 for a particular quality characteristic and the average repair cost is Rs. 200, determine the loss function.

Solution-

We know Taguchi quality loss function
L (x) = K (x-N)2
Where K = C/d²
C = Loss associated with the specification limit = 200
d = Deviation of the specification from the target values = 2 units
K = 200/(2)²  = 50
Loss Function L (x) = K (x-N)2  = 50 (11 – 10)2 = Rs. 50 Ans.

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