Krajewski Om9 Ppt 14 [Compatibility Mode]

Operations PlanningOperations Planning14Operations Planning Operations Planning and Schedulingand Scheduling14 gg

ForFor Operations ManagementOperations Management 99ee

14 – 1Copyright © 2010 Pearson Education, Inc. Publishing as Prentice Hall.

For For Operations Management, Operations Management, 99eeby Krajewski/Ritzman/Malhotra by Krajewski/Ritzman/Malhotra © © 2010 2010 Pearson EducationPearson Education

PowerPoint Slides PowerPoint Slides by Jeff Heylby Jeff Heyl

Across the OrganizationAcross the Organization

Operations planning and scheduling isOperations planning and scheduling is the process of making sure that demand and supply plans are in balance at all levelsSales and operations planning and Sa es a d ope at o s p a g a dschedulingRequires managerial inputs from all of theRequires managerial inputs from all of the firm’s functionsEach function is affected by the planEach function is affected by the plan


Across the OrganizationAcross the Organization

TABLE 14.1 | TYPES OF PLANS WITH OPERATIONS PLANNING AND|| SCHEDULING

Term DefinitionSales and operations A time-phased plan of future aggregate resource levels pplan (S&OP)

p p gg gso that supply is in balance with demand throughout the organization

Aggregate plan Another term for the sales and operations plan

Production plan A manufacturing firm’s sales and operations plan that centers on production rates and inventory holdings

Staffing plan A sales and operations plan for a service firm, which g p p p ,centers on staffing and on other human resource-related factors

Resource plan An intermediate, more detailed, step in the planning process that lies between S&OP and schedulingprocess that lies between S&OP and scheduling

Schedule A detailed plan that allocates resources over shorter time horizons to accomplish specific tasks


Stages in Planning and SchedulingStages in Planning and Scheduling

Aggregationgg gProduct familiesWorkforceWorkforce Time

Th l ti hi f ti l dThe relationship of operations plans and schedules to other plans

A business plan An annual plan or financial plan Resource planningThe lowest planning level is scheduling


p g g

Stages in Planning and SchedulingStages in Planning and Scheduling

Business orl l

Operationst t

Figure 14.1 – The Relationship of Sales and Operations Plans and

annual plan strategySchedules to Other Plans

SalesPlan

OperationsPlan

Sales and Operations Plan

Forecasting Constraintmanagement

R Pl i ( f t i )R Pl i ( i )• Master production schedule• Material requirements planning

Resource Planning (manufacturing)• Workforce schedule• Materials and facility resources

Resource Planning (services)

• Employee and equipment schedules• Production order schedules

Scheduling• Employee schedules• Facility schedules

Scheduling


• Purchase order schedulesy

• Customer schedules

Managing DemandManaging Demand

Matching supply with demand becomes challenging when forecasts call for uneven d d ttdemand patternsDemand management, the process of changing demand patterns using one or more demand options


Managing DemandManaging Demand

TABLE 14.2 | DEMAND AND SUPPLY OPTIONS FOR|| OPERATIONS PLANNING AND SCHEDULING

Demand Options Supply OptionsComplementary Anticipation inventoryComplementaryproducts

Anticipation inventory

Promotional pricing Workforce adjustment (hiring or layoffs)Prescheduled Workforce utilization (overtime andPrescheduled appointments

Workforce utilization (overtime and undertime)

Reservations Part-time workers and subcontractorsRevenue management Vacation schedulesBacklogs Workforce schedulesBackorders Job and customer sequenceqStockouts Expediting


Sales and Operations PlansSales and Operations Plans

C rrent machine capacitiesOperations

C stomer needsDistribution and marketing

Current machine capacities Plans for future capacities Workforce capacities Current staffing level

Customer needs Demand forecasts Competition behavior

Materials Accounting and financeAggregate

planSupplier capabilities Storage capacity Materials availability

MaterialsCost data Financial condition of firm

Accounting and finance

Engineering Human resourcesNew products Product design changes Machine standards

EngineeringLabor-market conditions Training capacity

Human resources


Figure 14.2 – Managerial Inputs from Functional Areas to Sales and Operations Plans


Information inputsSupply options

Anticipation inventoryWorkforce adjustmentWorkforce utilizationPart-time workersSubcontractorsVacation schedules

Planning strategiesChase strategyLevel strategyMi d t t


Mixed strategy


Constraints and costsSix steps in the sales and operations planning process

TABLE 14.3 | TYPES OF COSTS WITH SALES AND OPERATIONS PLANNING

Cost DefinitionRegular time Regular-time wages plus benefits and pay for vacationsOvertime Wages paid for work beyond the normal workweek exclusive

of fringe benefitsof fringe benefitsHiring and layoff Cost of advertising jobs, interviews, training programs, scrap

caused by inexperienced employees, exit interviews, severance pay, and retraining

Inventory holding Capital, storage and warehousing, pilferage and obsolescence, insurance, and taxes

Backorder and stockout Costs to expedite past-due orders, potential cost of losing a customer




Figure 14.3 – Sales and Operations Plan for Make-to-Stock Product Family


Update S&OPDemandGather Update S&OP spreadsheets

3

Demand planning

2

Gather data

1

Finalize and

communicate

Executive S&OP

meetingConsensus

meeting46 5 4


Using SpreadsheetsUsing Spreadsheets


Figure 14.4 – Manufacturer’s Plan Using a Spreadsheet and Mixed Strategy

Using Chase and Level StrategiesUsing Chase and Level Strategies

EXAMPLE 14.1A large distribution center must develop a staffing plan that minimizes total costs using part-time stockpickersFirst level strategy that meets demand with the minimum use ofFirst level strategy that meets demand with the minimum use of undertime and not consider vacation schedulingEach part-time employee can work a maximum of 20 hours per week on regular timeInstead of paying undertime, each worker’s day is shortened during slack periods and overtime can be used during peakduring slack periods and overtime can be used during peak periods

1 2 3 4 5 6 Total

Forecasted demand 6 12 18 15 13 14 78



Currently, 10 part-time clerks are employed. They have not been subtracted from the forecasted demand shown. Constraints and cost information are as follows:a. The size of training facilities limits the number of new hiresa. The size of training facilities limits the number of new hires

in any period to no more than 10.b. No backorders are permitted.c. Overtime cannot exceed 20 percent of the regular-time

capacity in any period. The most that any part-time employee can work is 1.20(20) = 24 hours per week.

d. The following costs can be assigned:

Regular-time wage rate $2 000/time period at 20 hrs/weekRegular-time wage rate $2,000/time period at 20 hrs/weekOvertime wages 150% of the regular-time rateHires $1,000 per person


Layoffs $500 per person


SOLUTIONa. Chase StrategyThis strategy simply involves adjusting the workforce as needed to meet demand as shown in Figure 14 5 Rows in theneeded to meet demand, as shown in Figure 14.5. Rows in the spreadsheet that do not apply (such as inventory and vacations) are hidden. The workforce level row is identical to the forecasted demand row A large number of hirings andthe forecasted demand row. A large number of hirings and layoffs begin with laying off 4 part-time employees immediately because the current staff is 10 and the staff level required in period 1 is only 6 However many employees such as collegeperiod 1 is only 6. However, many employees, such as college students, prefer part-time work. The total cost is $173,500, and most of the cost increase comes from frequent hiring and layoffs, which add $17,500 to the cost of utilized regular-timelayoffs, which add $17,500 to the cost of utilized regular time costs.




Figure 14.5 – Spreadsheet for Chase Strategy


b. Level StrategyIn order to minimize undertime, the maximum use of overtime possible must occur in the peak period. For this particular level strategy (other workforce options are possible), the moststrategy (other workforce options are possible), the most overtime that the manager can use is 20 percent of the regular-time capacity, w, so

1.20w = 18 employees required in peak period (period 3)

w = = 15 employees18

A 15-employee staff size minimizes the amount of undertime

w 15 employees1.20

for this level strategy. Because the staff already includes 10 part-time employees, the manager should immediately hire 5 more. The complete plan is shown in Figure 14.6. The total

t i $164 000


cost is $164,000.



Figure 14.6 – Spreadsheet for Level Strategy

Application Application 1414..11

The Barberton Municipal Division of Road Maintenance is charged with road repair in the city of Barberton and surrounding area. Cindy Kramer, road maintenance director, must submit a staffing plan for the next year based on a set

h d l f i d th it b d t K ti tschedule for repairs and on the city budget. Kramer estimates that the labor hours required for the next four quarters are 6,000, 12,000, 19,000, and 9,000, respectively. Each of the 11 workers on the workforce can contribute 520 hours per quarterworkers on the workforce can contribute 520 hours per quarter. Overtime is limited to 20 percent of the regular-time capacity in any quarter. Subcontracting is not permitted.Payroll costs are $6,240 in wages per worker for regular time worked up to 520 hours, with an overtime pay rate of $18 for each overtime hour. Although unused overtime capacity has no

d l i i id $12 h Th fcost, unused regular time is paid at $12 per hour. The cost of hiring a worker is $3,000, and the cost of laying off a worker is $2,000.



Use a chase strategy for the Barberton Municipal Division that varies the workforce level without using overtime. Undertime should be minimized, except for the minimal amount mandated pbecause the quarterly requirements are not integer multiples of 520 hours. (Students complete highlighted sections)



Quarter1 2 3 4 Total

F t d 6 000 12 000 19 000 9 000 46 000Forecasted demand (hrs)

6,000 12,000 19,000 9,000 46,000

Workforce level (workers)

12 9137 1824(workers)Undertime (hours) 240 1,320Overtime (hours) 0 0

2400

3600

4800

Utilized time (hours)

6,000 46,000

Hires (workers) 1 26

19,000

13

9,000

0

12,000

12Hires (workers) 1 26Layoffs (workers) 0 19

130

019

120



What is the total cost of this plan?

Costs per Quarter1 2 3 4 Total

Utilized time $72,000 $552,000$144,000 $228,000 $108,000Undertime 2,880 15,840Overtime 0 0Hires 3 000 78 000

5,7600

36 000

2,8800

39 000

4,32000Hires 3,000 78,000

Layoffs 0 38,000Total Cost $683,840

36,0000

39,0000

038,000



Find a level plan for the Barberton Municipal Division that allows no delay in road repair and minimizes undertime. Overtime can be used to its limits in any quarter. Given that the d d k i t 3 tdemand peaks in quarter 3, we get:

1.20w = 36.54 employee-period equivalents19,000

520 =1.20w

w = 30.45 or 31 employees

36.54 employee period equivalents 520



Q tQuarter1 2 3 4 Total

Forecasted 6,000 12,000 19,000 9,000 46,000Forecasted demand (hrs)

6,000 12,000 19,000 9,000 46,000

Workforce level (workers)

31 31 31 31 124 (workers)Undertime (hours) 10,120Overtime (hours) 0

4,1200

02,880

7,1200

21,3602,880

Utilized time (hours)

6,000

Hires (workers) 20

12,000

0

16,120

0

9,000

0

43,120

20Hires (workers) 20Layoffs (workers) 0

00

00

00

200



What is the total cost of this level workforce plan?

Costs per Quarter

What is the total cost of this level workforce plan?

Costs per Quarter1 2 3 4 Total

Utilized time $72,000 $517,440$108,000$193,440$144,000Undertime 121,440 256,320Overtime 0 51,840

85,4400

051,840

49,4400

Hires 60,000 60,000Layoffs 0 0

Total Cost $885 600

00

00

00

Total Cost $885,600



A mixed strategy considers and implements a fuller range of reactive alternatives than any one “pure” strategy.Now propose a plan of your own for the Barberton MunicipalNow propose a plan of your own for the Barberton Municipal Division. Use the chase strategy as a base, but find a way to decrease the cost of hiring and layoffs by selectively using some overtime. (Students complete highlighted sections)( p g g )



Quarter1 2 3 4 Total

Forecasted demand 6,000 12,000 19,000 9,000 46,000W kf l l 12 8524 31 18Workforce level Undertime (hours)Overtime (hours)

12240

0

851,0802,880

24480

0

310

2,880

18360

0Overtime (hours)Utilized time (hours)Hires (workers)

06,000

1

2,88043,120

20

012,000

12

2,88016,120

7

09,000

0Layoffs (workers) 0 130 0 13

Several solutions are possible The key idea in creating this oneSeveral solutions are possible. The key idea in creating this one is hiring only 7 employees in quarter 3, while using overtime to its maximum limit and eliminating undertime for that quarter. Hiring fewer in quarter 3 allows the number of layoffs in quarter 4 to


fewer in quarter 3 allows the number of layoffs in quarter 4 to drop to only 13, down from 19.


What is the cost of your mixed strategy plan?

Costs per QuarterCosts per Quarter1 2 3 4 Total

Utilized time $72,000 $144,000 $193,440 $108,000 $517,440UndertimeOvertime

12,96051,840

2,8800

5,7600

051,840

4,3200

HiresLayoffs

Total Cost

60,00026,000

$668 240

3,0000

36,0000

21,0000

026,000

Total Cost $668,240


SchedulingScheduling

Takes operations and scheduling processTakes operations and scheduling process from planning to execution and requires gathering data from sources such as demand forecasts, resource availability from the sales and operations plan, and

ifi t i t f l dspecific constraints from employees and customers. Generates a work schedule for employees or sequences of jobs oremployees or sequences of jobs or customers at workstations.


Gantt ChartsGantt Charts

The job or activity progress chartThe job or activity progress chartThe workstation chart

C t d t

Job 4/20 4/22 4/23 4/24 4/25 4/264/214/17 4/18 4/19

Current date

Ford

Start activity

Finish activity

Nissan

Scheduled activity time

Actual progress

N d ti

Pontiac

Nonproductive time


Figure 14.7 – Gantt Progress Chart for an Auto Parts Company

Gantt ChartsGantt Charts

Time

Workstation 7am 12 pm8am 9am 10am 11am 1pm 2pm 3pm 4pm 5pm 6pm

Time

Operating Room A

Dr. Jon Adams Dr. Aubrey Brothers Dr. Alaina Bright

Operating Room B

Dr. Gary Case Dr. Jeff Dow Dr. Madeline Easton

Operating Room C

Dr. Dan GillespieDr. Jordanne FlowersRoom C

Figure 14.8 – Gantt Workstation Chart for Operating Rooms at a Hospital


Scheduling EmployeesScheduling Employees

Translate the staffing plan into specificTranslate the staffing plan into specific schedules of work for each employeeConstraintsConstraints

Technical constraintsL l d b h i l id tiLegal and behavioral considerationsPsychological needs of workers

Rotating scheduleFixed scheduleFixed schedule


Scheduling EmployeesScheduling Employees

Steps in developing a workforce scheduleSteps in developing a workforce scheduleStep 1: Find all the pairs of consecutive daysStep 2: If a tie occurs choose one of the tiedStep 2: If a tie occurs, choose one of the tied

pairs, consistent with the provisions written into the labor agreement

Step 3: Assign the employees for the selected pair of days off

Step 4: Repeat steps 1 – 3 until all of the requirements have been satisfied


Developing a Workforce ScheduleDeveloping a Workforce Schedule

EXAMPLE 14.2The Amalgamated Parcel Service is open seven days a week. The schedule of requirements is

Day M T W Th F S Su

Required number of employees 6 4 8 9 10 3 2Required number of employees 6 4 8 9 10 3 2

The manager needs a workforce schedule that provides twoThe manager needs a workforce schedule that provides two consecutive days off and minimizes the amount of total slack capacity. To break ties in the selection of off days, the scheduler gives preference to Saturday and Sunday if it isscheduler gives preference to Saturday and Sunday if it is one of the tied pairs. If not, she selects one of the tied pairs arbitrarily.



SOLUTIONFriday contains the maximum requirements, and the pair S – Su has the lowest total requirements. Therefore, Employee 1 is scheduled to work Monday through Friday.scheduled to work Monday through Friday.Note that Friday still has the maximum requirements and that the requirements for the S – Su pair are carried forward because these are Employee 1’s days off These updatedbecause these are Employee 1 s days off. These updated requirements are the ones the scheduler uses for the next employee.

ff fThe day-off assignments for the employees are shown in the following table.


Developing a Workforce ScheduleDeveloping a Workforce ScheduleScheduling Days Off

M T W Th F S Su Employee CommentsM T W Th F S Su Employee Comments

6 4 8 9 10 3 2 1 The S–Su pair has the lowest total requirements. Assign Employee 1 to a M-F schedule.

5 3 7 8 9 3 2 2 The S–Su pair has the lowest total requirements. Assign E l 2 t M F h d lEmployee 2 to a M-F schedule.


3 1 5 6 7 3 2 4 The M–T pair has the lowest total requirements. Assign E l 4 t W S h d lEmployee 4 to a W-Su schedule.


2 0 3 4 5 2 1 6 The M–T pair has the lowest total requirements. Assign Employee 6 to a W Su scheduleEmployee 6 to a W-Su schedule.


1 0 1 2 3 1 0 8 Four pairs have the minimum requirement and the lowest total Choose the S Su pair according to the tielowest total. Choose the S–Su pair according to the tie-breaking rule. Assign Employee 8 to a M-F schedule.

0 0 0 1 2 1 0 9 Arbitrarily choose the Su–M pair to break ties because the S–Su pair does not have the lowest total requirements. Assign Employee 9 to a T-S schedule.


0 0 0 0 1 0 0 10 Choose the S–Su pair according to the tie-breaking rule. Assign Employee 10 to a M-F schedule.

Developing a Workforce ScheduleDeveloping a Workforce ScheduleScheduling Days Off

M T W Th F S Su Employee CommentsM T W Th F S Su Employee Comments


5 3 7 8 9 3 2 2 The S–Su pair has the lowest total requirements. Assign E l 2 t M F h d l

The S–Su pair has the lowest total requirements. Assign Employee 1 to a M-F schedule.The S–Su pair has the lowest total requirements. Assign E l 2 t M F h d l

6 4 8 9 10 3 2 1

5 3 7 8 9 3 2 2Employee 2 to a M-F schedule.


3 1 5 6 7 3 2 4 The M–T pair has the lowest total requirements. Assign E l 4 t W S h d l

Employee 2 to a M-F schedule.The S–Su pair has the lowest total requirements. Assign Employee 3 to a M-F schedule.

4 2 6 7 8 3 2 3

3 1 5 6 7 3 2 4 The M–T pair has the lowest total requirements. Assign E l 4 t W S h d lEmployee 4 to a W-Su schedule.


2 0 3 4 5 2 1 6 The M–T pair has the lowest total requirements. Assign Employee 6 to a W Su schedule

Employee 4 to a W-Su schedule.3 1 4 5 6 2 1 5 The S–Su pair has the lowest total requirements. Assign

Employee 5 to a M-F schedule.2 0 3 4 5 2 1 6 The M–T pair has the lowest total requirements. Assign

Employee 6 to a W Su scheduleEmployee 6 to a W-Su schedule.2 0 2 3 4 1 0 7 The S–Su pair has the lowest total requirements. Assign

Employee 7 to a M-F schedule.1 0 1 2 3 1 0 8 Four pairs have the minimum requirement and the

lowest total Choose the S Su pair according to the tie

Employee 6 to a W-Su schedule.2 0 2 3 4 1 0 7 The S–Su pair has the lowest total requirements. Assign

Employee 7 to a M-F schedule.1 0 1 2 3 1 0 8 Four pairs have the minimum requirement and the

lowest total Choose the S Su pair according to the tielowest total. Choose the S–Su pair according to the tie-breaking rule. Assign Employee 8 to a M-F schedule.


lowest total. Choose the S–Su pair according to the tie-breaking rule. Assign Employee 8 to a M-F schedule.






In this example, Friday always has the maximum requirements and should be avoided as a day off The final schedule for the

Final Schedule

and should be avoided as a day off. The final schedule for the employees is shown in the following table.

Employee M T W Th F S Su Total

1 X X X X X off off

2 X X X X X off off

3 X X X X X off off

4 off off X X X X X

5 X X X X X off off

6 off off X X X X X

7 X X X X X off off

8 X X X X X off off

9 off X X X X X off9 off X X X X X off

10 X X X X X off off

Capacity, C 7 8 10 10 10 3 2 50

Requirements, R 6 4 8 9 10 3 2 42


Requirements, R 6 4 8 9 10 3 2 42

Slack, C – R 1 4 2 1 0 0 0 8

Sequencing Jobs at a WorkstationSequencing Jobs at a Workstation

Priority sequencing rulesPriority sequencing rulesFirst-come, first-served (FCFS)

Performance measuresEarliest due date (EDD)

Flow time

Past due (also referred to as tardiness)

Flow time = Finish time + Time since job arrived at workstation

Past due (also referred to as tardiness)


Using the FCFS RuleUsing the FCFS Rule

EXAMPLE 14.3Currently a consulting company has five jobs in its backlog. The time since the order was placed, processing time, and promised due dates are given in the following table. Determinepromised due dates are given in the following table. Determine the schedule by using the FCFS rule, and calculate the average days past due and flow time. How can the schedule be improved, if average flow time is the most critical?p , g

Customer Time Since Order Arrived (days ago)

Processing Time (days)

Due Date(days from now)

A 15 25 29

B 12 16 27

C 5 14 68

D 10 10 48

E 0 12 80


E 0 12 80


SOLUTIONa. The FCFS rule states that Customer A should be the first one

in the sequence, because that order arrived earliest—15 days ago. Customer E’s order arrived today, so it isdays ago. Customer E s order arrived today, so it is processed last. The sequence is shown in the following table, along with the days past due and flow times.

Customer Sequence

Start Time

(days)


Finish Time

(days)

Due Date

Days Past Due

Days Ago Since Order

Arrived

Flow Time

(days)

A

B

CC

D

E



SOLUTIONa. The FCFS rule states that Customer A should be the first one

in the sequence, because that order arrived earliest—15 days ago. Customer E’s order arrived today, so it isdays ago. Customer E s order arrived today, so it is processed last. The sequence is shown in the following table, along with the days past due and flow times.

Customer Sequence

Start Time

(days)


Finish Time

(days)

Due Date

Days Past Due


Arrived

Flow Time

(days)

27 14 12 53

41 + 10 = 51 48 3 10 61

15 40+ 25 = 25 29 00

25 + 16 = 41

A

B

C 41 + 10 51 48 3 10 61

51 + 14 = 65 68 0 5 70

65 + 12 = 77 80 0 0 77

C

D

E



The finish time for a job is its start time plus the processing time. Its finish time becomes the start time for the next job in the sequence, assuming that the next job is available for immediate processing. The days past due for a job is zero (0) if it d d t i l t d th fi i h ti Oth i itits due date is equal to or exceeds the finish time. Otherwise it equals the shortfall. The flow time for each job equals its finish time plus the number of days ago since the order first arrived at the workstation The days past due and average flow timethe workstation. The days past due and average flow time performance measures for the FCFS schedule are

Average days past due = = 3.4 days0 + 14 + 3 + 0 + 05

Average flow time = = 60.2 days40 + 53 + 61 + 70 + 775



b. The average flow time can be reduced. One possibility is the h i th f ll i t blsequence shown in the following table.

Customer Sequence

Start Time

(days)


Finish Time

(days)

Due Date

Days Past Due


Arrived

Flow Time

(days)(days) (days) Due Arrived (days)

D

E

C

B

A



b. The average flow time can be reduced. One possibility is the h i th f ll i t blsequence shown in the following table.

Customer Sequence

Start Time

(days)


Finish Time

(days)

Due Date

Days Past Due


Arrived

Flow Time

(days)

0 + 10 = 10

(days) (days) Due Arrived (days)

D

E

48 0 10 20

10 + 12 = 22 80 0 0 22

C

B

A

22 + 14 = 36 68 0 5 41

36 + 16 = 52 27 25 12 64

52 + 25 = 77 29 48 15 92


5

5 5 9 8 5 9

This schedule reduces the average flow time from to 60.2 to



47.8 days—a 21 percent improvement. However, the past due times for jobs A and B have increased.

Software SupportSoftware Support

Computerized scheduling systems areComputerized scheduling systems are available to cope with the complexity of workforce schedulingworkforce schedulingSoftware is also available for sequencing jobs at workstationsjobs at workstationsAdvance planning and scheduling (APS)

tsystems



Revisit Example 14.3, where the consulting company has five jobs in its backlog. Create a schedule using the EDD rule, calculating the average days past due and flow time. In this case, does EDD outperform the FCFS rule?

SOLUTION

Customer Sequence

Start Time

(days)


Finish Time

(days)

Due Date

Days Past Due


Arrived

Flow Time

(days)

B

A

D

0 + 16 = 16

41 + 10 = 51 48 3 10 61

27 0 12 28

16 + 25 = 41 29 12 15 56

D

C

E

41 10 51 48 3 10 61

51 + 14 = 65 68 0 5 70

65 + 12 = 77 80 0 0 77


Application Application 1414..44Customer Sequence

Start Time


Finish Time

Due Date

Days Past


Flow Time q

(days)( y )

(days) Due Arrived (days)

B

A

0 + 16 = 16 27 0 12 28

16 + 25 = 41 29 12 15 56A

D

C

41 + 10 = 51 48 3 10 61

51 + 14 = 65 68 0 5 70

16 + 25 = 41 29 12 15 56

E 65 + 12 = 77 80 0 0 77

The days past due and average flow time performance measures for the EDD schedule are


28 + 56 + 61 + 70 + 71

By both measures, EDD outperforms the FCFS. However, th l ti f d i t (b) f E l 14 3 till h th



the solution found in part (b) of Example 14.3 still has the best average flow time of only 47.8 days.

Solved Problem Solved Problem 11

The Cranston Telephone Company employs workers who lay telephone cables and perform various other construction tasks. The company prides itself on good service and strives to complete all service orders within the planning period in which th i dthey are received.Each worker puts in 600 hours of regular time per planning period and can work as many as an additional 100 hours of p yovertime. The operations department has estimated the following workforce requirements for such services over the next four planning periods:

Planning Period 1 2 3 4

Demand (hours) 21,000 18,000 30,000 12,000



Cranston pays regular-time wages of $6,000 per employee per period for any time worked up to 600 hours (including undertime). The overtime pay rate is $15 per hour over 600 hours. Hiring, training, and outfitting a new employee costs $8 000 L ff t $2 000 l C tl 40$8,000. Layoff costs are $2,000 per employee. Currently, 40 employees work for Cranston in this capacity. No delays in service, or backorders, are allowed. Use the spreadsheet approach to answer the following questions:approach to answer the following questions:

a. Prepare a chase strategy using only hiring and layoffs. What are the total numbers of employees hired and laid off?are the total numbers of employees hired and laid off?

b. Develop a workforce plan that uses the level strategy, relaying only on overtime and undertime. Maximize the use of o ertime d ring the peak period so as to minimi e theof overtime during the peak period so as to minimize the workforce level and amount of undertime.

c. Propose an effective mixed-strategy plan.


gyd. Compare the total costs of the three plans.


a. The chase strategy workforce is calculated by dividing the demand for each period by 600 hours, or the amount or regular-time work for one employee during one period. This strategy calls for a total of 20 workers to be hired and 40 to b l id ff d i th f i d l Fi 14 9 h thbe laid off during the four-period plan. Figure 14.9 shows the “chase strategy” solution that OM Explorer’s Sales and Operations Planning with Spreadsheets solver produces. We simply hide any unneeded columns and rows in this generalsimply hide any unneeded columns and rows in this general-purpose solver.




Figure 14.9 – Spreadsheet for Chase Strategy


b. The peak demand is 30,000 hours in period 3. As each employee can work 700 hours per period (600 on regular time and 100 on overtime), the workforce level of the level strategy that minimizes undertime is 30,000/700 = 42.86, or 43 l Thi t t ll f th l t b43 employees. This strategy calls for three employees to be hired in the first quarter and for none to be laid off. To convert the demand requirements into employee-period equivalents divide the demand in hours by 600 Forequivalents, divide the demand in hours by 600. For example, the demand of 21,000 hours in period 1 translates into 35 employee-period equivalents (21,000/600) and demand in period 3 translates into 50 employee perioddemand in period 3 translates into 50 employee-period equivalents (30,000/600). Figure 14.10 shows OM Explorer’s spreadsheet for this level strategy that minimizes undertime.




Figure 14.10 – Spreadsheet for Level Strategy


c. The mixed-strategy plan that we propose uses a combination of hires, layoffs, and overtime to reduce total costs. The workforce is reduced by 5 at the beginning of the first period, increased by 8 in the third period, and reduced b 13 i th f th i d Fi 14 11 h th ltby 13 in the fourth period. Figure 14.11 shows the results.




Figure 14.11 – Spreadsheet for Mixed Strategy


d Th t t l t f th h t t i $1 050 000d. The total cost of the chase strategy is $1,050,000. The level strategy results in a total cost of $1,119,000. The mixed-strategy plan was $ , , gy pdeveloped by trial and error and results in a total cost of $1,021,000. Further improvements are possiblepossible.



The Food Bin grocery store operates 24 hours per day, 7 days per week. Fred Bulger, the store manager, has been analyzing the efficiency and productivity of store operations recently. Bulger decided to observe the need for checkout clerks on the fi t hift f th i d At th d f th th hfirst shift for a one-month period. At the end of the month, he calculated the average number of checkout registers that should be open during the first shift each day. His results showed peak needs on Saturdays and Sundaysshowed peak needs on Saturdays and Sundays.

S SDay M T W Th F S Su

Number of Clerks Required 3 4 5 5 4 7 8



Bulger now has to come up with a workforce schedule that guarantees each checkout clerk two consecutive days off but still covers all requirements.a. Develop a workforce schedule that covers all requirementsa. Develop a workforce schedule that covers all requirements

while giving two consecutive days off to each clerk. How many clerks are needed? Assume that the clerks have no preference regarding which days they have off.p g g y y

b. Plans can be made to use the clerks for other duties if slack or idle time resulting from this schedule can be determined. How much idle time will result from this schedule and onHow much idle time will result from this schedule, and on what days?



SOLUTIONa. We use the method demonstrated in Example 14.2 to

determine the number of clerks needed. The minimum number of clerks is eight.number of clerks is eight.

DayM T W Th F S Su3 4 5 5 4 7 8

off off X X X X X3 4 4 4 3 6 7

M T W Th F S SuRequirementsClerk 1R i t 3 4 4 4 3 6 7

off off X X X X XRequirementsClerk 2Requirements 3 4 3 3 2 5 6Clerk 3RequirementsClerk 4

X X X off off X X2 3 2 3 2 4 5X X X off off X X



1 2 1 3 2 3 4

DayM T W Th F S Su

RequirementsX off off X X X X0 2 1 2 1 2 3

off off X X X X X

Clerk 5RequirementsClerk 6 off off X X X X X

0 2 0 1 0 1 2X X off off X X X0 1 0 1 0 0 1

Clerk 6RequirementsClerk 7R i t 0 1 0 1 0 0 1

X X X X off off X0 0 0 0 0 0 0

RequirementsClerk 8Requirements

The minimum number of clerks is eight.



Documents

Krajewski Om9 Ppt 14 [Compatibility Mode]