Quality Engineering
Consider the following quality data for three different manufacturers of automobile weatherstrips:
Weatherstrip Bulb Dimension
Specification y=20 +or 4mm
supplier

mean

variance

Cp

Cpk

%Defects

$Defects

Warranty Cost ($)

I

20.0

(4/3)2

1.0

1.0

0.270



II

18.0

(2/3)2

2.0

1.0

0.135



III

17.2

(2/5)2

3.33

1.0

0.135



Assume a customer loss per defective unit of $1450; cost of the weatherstrip is $150, and a customer specified functional tolerance of ?0 = ± 5mm. Assume the annual production rate is 200,000 units.
1. Confirm the entries in the %Defects column.
2. Calculate the $Defects for each supplier, and fill in the table.
3. Using a quadratic loss function of the form:
Average Loss = k [ s2 + ( mean  target )2 ]
calculate the $ loss due to variation, and fill in the table.
4. What is the sigma level for each supplier?
5. What is the value of manufacturing specifications to customers?
6. Select the best supplier, and explain your choice.