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Chapter 13: Aggregate Planning |
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Cornwell Glass
Cornwell Glass produces replacement automobile glass for all makes of cars. Cornwell has a sophisticated forecasting system that uses data from past years to find seasonal factors and long-term trends. The system uses data from past weeks to find recent trends. The following table presents the forecasted demands for the coming year on a weekly basis.
Week |
|
Demand |
Week |
|
Demand |
April |
15 |
1,829 |
November |
4 |
1,864 |
|
22 |
1,820 |
|
11 |
1,989 |
|
29 |
1,887 |
|
18 |
2,098 |
May |
6 |
1,958 |
|
25 |
2,244 |
|
13 |
2,011 |
December |
2 |
2,357 |
|
20 |
2,063 |
|
9 |
2,368 |
|
27 |
2,104 |
|
16 |
2,387 |
June |
3 |
2,161 |
|
23 |
2,402 |
|
10 |
2,258 |
|
30 |
2,418 |
|
17 |
2,307 |
January |
6 |
2,417 |
|
24 |
2,389 |
|
13 |
2,324 |
July |
1 |
2,434 |
|
20 |
2,204 |
|
8 |
2,402 |
|
27 |
2,188 |
|
15 |
2,385 |
February |
3 |
2,168 |
|
22 |
2,330 |
|
10 |
2,086 |
|
29 |
2,323 |
|
17 |
1,954 |
August |
5 |
2,317 |
|
24 |
1,877 |
|
12 |
2,222 |
March |
3 |
1,822 |
|
19 |
2,134 |
|
10 |
1,803 |
|
26 |
2,065 |
|
17 |
1,777 |
September |
2 |
1,973 |
|
24 |
1,799 |
|
9 |
1,912 |
|
31 |
1,803 |
|
16 |
1,854 |
April |
7 |
1,805 |
|
23 |
1,763 |
|
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|
|
30 |
1,699 |
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October |
7 |
1,620 |
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|
14 |
1,689 |
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|
21 |
1,754 |
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|
28 |
1,800 |
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Cornwell uses these forecasts for its production planning. It manufactures several types of glass, and demand is aggregated across products and measured in pounds.
Cornwell must consider the costs of hiring or firing workers; using overtime; subcontracting; and holding inventory or running out of the product. The holding cost for glass is $.12 per pound per week. The company estimates that the cost of a late order is $20 per pound per week late.
Cornwell currently costs out each hire at $5.63 per pound (based on training costs and production rates per worker). It costs out each fire at $15.73 per pound (based on unemployment compensation and loss of good will). The company currently has the capacity to manufacture 1,900 pounds of glass per week. This capacity cannot be exceeded under any plan. At most, 2,000 pounds can be subcontracted in a given week, and overtime is limited to 250 pounds per week. Glass that is manufactured during overtime costs $8 per pound more than glass manufactured during regular time. Glass that is subcontracted costs $2 more per pound than glass that is produced during overtime.
The current inventory is 73 units, and currently production is working at full capacity, 1,900 units. Cornwell has not been able to determine whether demands not met in the current month can be met later or whether these orders are lost.
DISCUSSION QUESTIONS
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