Problems 639 - Yolaadrielcollazo.yolasite.com/resources/MPS_Ejercicios.pdfProblems considerations...

Problems

considerations for master production sched-uling?

PROBLEMS

Review Problems

1. Complete the MPS record in Fig. 15.12 for asingle item. At present there are 35 units ofthe item in inventory. Each order is for 60units.

2. Complete the MPS record shown in Fig.15.13 for a single item. There are currently75 units of the item in inventory. Each orderis for 100 units.

3. The following data apply to an end item.

• The forecasts for the next 10 weeks are 30,20, 35, 50, 25, 25, 0, 40, 0, and 50 units.

• The current on-hand inventory is 70 units.• The order policy is to produce in lots of

75.

639

• The booked customer orders for the item,starting with week 1, are 22, 30, 15, 9, 0,0, 5, 3, 7, and 0 units.

• At present, there are no MPS quantitiesfor this item.

a. Develop a prospective MPS and calculatethe available-to-promise inventory quan-tities.

b. A customer needs 100 units of this item.What is the earliest shipping date for theentire order that you could give the cus-tomer?

4. You have the following information for a par-ticular end item.

• The forecasts for the next 10 weeks are 50,100, 100, 75, 75, 0, 0, 50, 50, and 75 units.

• The current on-hand inventory is 25 units.• The order policy is to produce in lots

of 100 units. There is an MPS quantityof 100 units scheduled for completion inweek 1.

FIGURE 15.12

Quantity on Hand: 35

Forecast

Customer orders (booked)

Projected on-hand inventory

MPS quantity

Week

1

17

15

2

15

16

3

25

5

4

25

11

5

20

9

6

27

0

7

30

5

8

35

0

FIGURE 15.13


Forecast



MPS quantity

January

1

75

40

2

65

10

3

50

55

4

45

0

February

5

65

35

6

65

70

7

75

0

8

75

0

640 CHAPTER 15 I Master Production Scheduling

• The booked customer orders, startingwith week 1, are 60, 45, 20, 15, 0, 0, 0, 0,0, and 0 units.

a. Develop a prospective MPS and calculatethe available-to-promise inventory quan-tities.Three customer orders have arrived inb.the following sequence.

Order123

Quantity507030

Week Desired234

Which of the orders would you accept?(Assume that you must commit to themin sequence and that you cannot changethe desired shipping dates or the MPS.)What would the updated MPS look like?

5. Complete the MPS record in Fig. 15.14 for asingle item. At present, there are 50 units ofthe item in inventory. Each order is for 125units.

6. You have the partially completed MPS re-cord for orange peelers in Fig. 15.15.a. Develop the MPS and calculate the ATP

inventory quantities if the current quan-tity on hand is 400 peelers and the policyis to order 500 each time.

b. Four customer orders arrived in the fol-lowing sequence.

Order1234

Quantity500100300350

Week Desired4517

Assuming you must commit to the orders inthe sequence of arrival and you cannotchange the desired shipping dates or yourMPS, which orders would you accept?

7. Morrison Electronics has forecasted the fol-lowing demand for one of its products for thenext eight weeks: 70, 70, 65, 60, 55, 85, 75,and 85. The booked customer orders for thisproduct, starting in week 1, are 50, 60, 55,40, 35, 0, 0, and 0 units. The current on-hand inventory is 100 units, and the orderquantity is 150 units.a. Develop a prospective MPS (including

ATP quantities) for this product.b. The marketing department at Morrison

has revised its forecasts. Starting withweek 1, the new forecasts are 70, 70, 75,70, 70, 100, 100, and 110 units. Prepare arevised MPS record, assuming that theprospective MPS you developed in part(a) doesn't change. Comment on the sit-uation that Morrison now faces.

8. a. Complete the MPS in Fig. 15.16 for a sin-gle end item. Currently 500 units are ininventory; Each order is for 800 units.

FIGURE 15.14


Forecast



MPS quantity

Available-to-promise (ATP)inventory

Week

1

10

12

2

15

9

3

20

11

4

30

5

5

40

2

6

60

0

7

80

4

8

120

0

9

120

0

10

120

0

Problems 641

FIGURE 15.15


Forecast



MRS quantity


Week

1

550

300

2

300

350

3

400

250

4

450

250

5

300

200

6

350

150

7

200

100

8

300

100

9

450

100

10

400

100

b. Three customer orders have arrived inthe following sequence.

Order123

Quantity600400425

Week Desired645

Assuming that you must commit to theorders in sequence, which orders wouldyou accept (rather than attempt to re-schedule)?Suppose that management wishes to ful-fill all the customer orders by the desiredshipping dates. Revise the MPS to ac-complish this task. What other factorsmust you consider when making this re-vision?

9. The Conestoga Wagon Company produces asingle product, a motorized child-sizedversion of the original Conestoga wagon.The following prospective MPS has beenproposed.

WeekUnits

150

250

340

430

530

650

There is one critical work station in theshop: the frame-building station. Eachwagon requires three direct labor hours atthis critical work station. The total direct la-bor requirement per unit is 18 hours,a. Using the method of overall factors, de-

termine the direct labor requirements atthe frame-building work station.

FIGURE 15.16


Forecast



MPS quantity


Week

1

300

150

2

100

3

400

225

4

600

200

5

600

300

6

800

7

600

8

800

275

9

500

10

600


b. Assume that the MPS was designed tomeet exactly forecasted requirementseach period and that there are no avail-able on-hand inventories. Suppose thatthe available labor hours at the frame-building work station are 150 hours perweek for weeks 1 and 2, and 120 hoursper week for weeks 3-6. Revise the MPSto ensure that no stockouts occur, capac-ity constraints are satisfied, and inventoryis minimized.

10. Marshall Fans produces a lightweight desk-top fan. A prospective MPS for the fan hasbeen proposed.

Month Jan Feb Mar Apr May JunUnits 300 400 200 400 500 750

Two critical work stations are involved in theproduction of the fan: 401A and 401B. His-torically, 401A has had 80 percent and 401Bhas had 20 percent of the total critical workstation hours.

The direct labor hours per unit are as fol-lows: critical work stations, 2.0; noncriticalwork stations, 3.0; and total, 5. Using themethod of overall factors, determine the di-rect labor requirements for each individualcritical work station and for the entire plant.

11. The Karry Kart Company produces twoproducts, a deluxe kart (DK) and a standardkart (SK). The following prospective MPShas been proposed for the two products.

Week

Item 1 2 3 4 5 6 TotalDK 50 50 30 30 30 30 220SK 60 — 60 — 60 — 180

The direct labor hours per unit are

ItemDKSK

Critical WorkStations (hr)

11.06.0

Noncritical Work TotalStations (hr) (hr)

4.0 15.04.0 10.0

There are three critical work stations: Z101,Z105, and Z107. Historically, Z101, Z105,and Z107 have accounted for 40 percent, 30

percent, and 30 percent of the direct laborhours, respectively.a. Create a load profile based on the pro-

spective MPS, using the method of over-all factors.

b. Suppose that the production plan speci-fied a total of 1100 direct labor hours ofwhich 750 hours are at the critical workstations. Do you see any potential prob-lems with the prospective schedule? If so,propose a better MPS.

Advanced ProblemsA computer package is recommended for Prob-lems 12, 15, 16, and 17.

12. The marketing department of NEVEDHome-help Products has forecasted the fol-lowing for the company's two products.

Month

ProductHome energy

controller (HEC)Home personal

robot (HPR)

Mar Apr May

1000 1200 600

200 160 180

The company has 450 units of HEC and 150units of HPR on hand. The company ordersHEC in lots of 400 units and HPR in lots of80 units. One lot of HEC is scheduled to bereceived in the second week of March. Thecompany has received the following orders.

Shipping Dates

Mar Apr

1 2 3 4 5 6 7 8HEC 150 160 150 145 100HPR 50 40 20 50

Management likes to have the MPS ex-pressed in weekly time periods and typicallyallocates monthly forecasts evenly over theweeks of the month. (Assume 4 weeks permonth.)a. Develop a prospective MPS for each

product.b. A potential customer is interested in buy-

ing 900 units of HEC and 150 units of

Problems 643

FIGURE 15.17


Production requirements



MPS quantity


Week

1

40

60

75

2

40

45

75

3

40

30

4

40

35

5

30

10

6

30

5

7

50

5

8

50

0

HPR. What is the earliest realistic datefor which marketing can promise deliveryof the HEC units? The HPR units?

c. The customer has decided to take deliv-ery of the two products at the same time.What is the earliest date on which mar-keting could deliver 900 units of HECand 150 units of HPR to the customer?

13. Complete the MPS record in Fig. 15.17.This partial record shows the production re-quirements for a single end item. There arecurrently 10 units on hand, and the orderpolicy is to produce in lots of 75. Lotsare scheduled for completion in weeks 1and 2.

14. The production requirements for an electricscrewdriver for the next six weeks are 20, 30,15, 20, 50, and 60 units. Marketing hasbooked orders totaling 25 units in the first(current) week and 10 units in the thirdweek. Currently, 50 screwdrivers are onhand. The policy is to order the exact quan-tity required to meet production require-ments each week.a. Develop the MPS record for the screw-

driver.b. A distributor of the screwdriver places an

order for 45 units. What is the appropriateshipping date for the entire order?

15. Production of 240 units in January, 320 unitsin February, and 240 units in March hasbeen approved for the seismic-sensory prod-

uct family manufactured at the Hilliard facil-ity of Sloan Automated, Inc. There are threeproducts in this family. The product mix ra-tio for products A, B, and C for the past twoyears has been 35 percent, 40 percent, and25 percent, respectively. There are 60 unitsof product C on hand. The company ordersproduct C in lots of 40 units and has ac-cepted orders of 25, 12, 8, 10, 2, and 3 ofproduct C in weeks 1-6, respectively. Pre-pare a prospective MPS for product C andcalculate the available-to-promise inven-tory quantities. Management wishes to allo-cate the monthly production requirementsevenly over the month. Assume that eachmonth has 4 weeks.

16. The master production scheduler at yourcompany has developed the prospectiveMPS shown in Fig. 15.18 for the three itemsyour company produces. There are two crit-ical work stations in the shop: WSA, which

Item

ABC

Month

Jan

3050-

Feb

70-70

Mar

3090-

Apr

75-

50

May

4050-

Jun

110-70

TotalUnits

355190190

FIGURE 15.18


has recorded 30 percent of the hours at thecritical work stations, and WSB, which hasrecorded the rest. Your production plan has aconstant work force size that yields 900hours per month, of which 300 hours totalare at the critical work stations. Work stationWSA has been allocated 90 hours per month,and WSB has been allocated 210 hours. Di-rect labor hours per unit are

ItemABC

CriticalWork

Stations213

NoncriticalWork

Stations465

Total678

a. Prepare a load profile for the prospectiveMPS using the method of overall factors.Comment on the feasibility of this sched-ule.

b. Prepare an alternative MPS to the one pro-posed by the master production scheduler

SELECTED REFERENCES

Bahl, H.C., and L.P. Ritzman. "An Empirical Investigationof Different Strategies for Material Requirements Plan-ning." Journal of Operations Management, vol. 3, no. 2(1983), pp. 67-77.

Berry, W.L., T.G. Schmitt, and T.E. Vollmann. "Capacity-Planning Techniques for Manufacturing Control Systems:Information Requirements and Operational Features."Journal of Operations Management, vol. 3, no. 1 (November1982), pp. 13-25.

Berry, W.L., T.E. Vollmann, and D.C. Whybark. Master Pro-duction Scheduling: Principles and Practices. Falls Church, Va.:American Production and Inventory Control Society, Inc.,1979.

Bitran, G.R., and A.C. Hax. "On the Design of HierarchicalProduction Planning Systems." Decision Sciences, vol. 8,no. 1 (January 1977), pp. 28-55.

Bruggeman, J.J., and S. Haythornthwaite. "The MasterSchedule." APICS—The Performance Advantage (October1991), pp. 44-46.

Chung, C.H., and L. Krajewski. "Planning Horizons for Mas-ter Production Scheduling." Journal of Operations Manage-ment, vol. 4, no. 4 (August 1984).

Everdell, R., and W. Chamberlain. "Master Scheduling in aMul t i -Plant Environment." Proceedings of the 23rd AnnualAmerican Production and Inventory Control Society Conference.Los Angeles (October 14-17, 1980), pp. 421^129.

that satisfies the labor budget specified inthe production plan. Assume that themaster production scheduler adhered tothe following guidelines.

Cumulative ProductionRequired by End

of Month

MonthJanFebMarAprMayJun

A0

100100210210355

B5050140140190190

C07070130130190

For example, you need no units of A inJanuary, but you do need 100 by the end ofFebruary. Also, you need no units of A inMarch, but by the end of April the cumula-tive production of A most be 210 units be-cause you need 110 units in April.

Hax, A.C., and H.C. Meal. "Hierarchical Integration of Pro-duction Planning and Scheduling." In M. A. Geisler, ed.,Studies in Management Sciences, vol. 1, Logistics. New York:North Holland-American Elsevier, 1975, pp. 53-69.

Ling R. "Master Scheduling in a Make-to-Order Environ-ment." Inventories and Production, vol. 1, no. 3 (July-August 1981), pp. 17-21.

Mangiameli , P., and L. Krajewski. "The Effects of Work-force Strategies on Manufacturing Operations." Journal: ofOperations Management, vol. 3, no. 4 (August 1983), pp.183-196.

Newson, E.P. "Multi-I tem Lot Size Scheduling by Heuristic,Part I: With Fixed Resources; Part II: With Variable Re-sources." Management Science, vol. 21, no. 10 (June 1975),pp. 1186-1203.

Orlicky, J. Material Requirements Planning. New York: Mc-Graw-Hill , 1975.

Proud, J.F. "Controlling the Master Schedule." Productionand Inventory Management, vol. 22, no. 2 (Second Quarter1981), pp. 78-90.

Vollmann, T.E., W.L. Berry, and D.C. Whybark. Manufactur-ing Planning and Control Systems. Homewood, 111.: Irwin,1992.

Wight, O. Production and Inventory Management in the ComputerAge. Boston: Cahners Books, 1974.

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