You are the SQE (Supplier Quality Engineer) at Turko Car Corp. You outsource som

Question

You are the SQE (Supplier Quality Engineer) at Turko Car Corp. You outsource some components and parts used in the production of cars at Turko. One of those parts is a rubber strip used to seal the doors of the cars. It has a specification on width of 20±4 mm. There are three suppliers of this rubber strip. As an ambitious engineer as you are, you run a quality survey on the strips and obtained the following results:

Field experience shows that when the width of the weather strip is 5 mm below the target, the seal begins to leak and about 50 percent of the customers will complain and they insist on replacing the seals. Replacement cost is $60 per car. When the strip width exceeds 25 mm, it becomes very difficult to close the doors, and again customers will ask to have the weather strip replaced. Over the past 2 years, the three suppliers had the following number of parts out of spec in deliveries of 250,000 parts:

OzL: 0.27%; EbU: 0.135%; MaS: 0.135%.

a) Compare the three suppliers on the basis of loss function.
b) Compare the three suppliers on the basis of cost of defective units.

Supplier Mean Width Variance s2 CPK OzL 20.0 1.778 1.0 EbU 18.0 0.444 1.0 MaS 17.2 0.160 1.0

Explanation / Answer

Using Taguchi loss function

Loss in dollars = Constant (K) (actual value – target value)2

And

Avg Taguchi loss per item = K [sd2 + (process mean – target)2]

First for all the three suppliers find out K

For Ozl supplier

$60 = K (20 -20)2 = indeterminate

For Ebu Supplier

$60 = K (18 -20)2

Then K = 15

For Mas Supplier

$60 = K (17.2 – 20)2

K = 10.71

Ozl                                          Indeterminate

Ebu    Avg TLF = K {2 + (mean – target)2} = 15 (0.444 + 4) = 66.66

Mas = 10.71( 0.16 + 5.6) = 61.69

Ozl                                                          EbU                        MaS

% defective                        0.27%                                                    0.135%                  0.135%

Defective in Nos               0.27x250000= 67500                        33750                    33750

Cost($)                                                 60 X 67500 = 4,050,000                   2,025,000             2,025,000

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