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Managing Capacity. © 2008 Pearson Prentice Hall --- Introduction to Operations and Supply Chain Management, 2/e --- Bozarth and Handfield, ISBN: 0131791036.

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Presentation on theme: "Managing Capacity. © 2008 Pearson Prentice Hall --- Introduction to Operations and Supply Chain Management, 2/e --- Bozarth and Handfield, ISBN: 0131791036."— Presentation transcript:

1 Managing Capacity

2 © 2008 Pearson Prentice Hall --- Introduction to Operations and Supply Chain Management, 2/e --- Bozarth and Handfield, ISBN: Chapter 8, Slide 2 Chapter Objectives Be able to:  Explain what capacity is, how firms measure capacity, and the difference between theoretical and rated capacity,  Describe the pros and cons associated with three different capacity strategies: lead, lag, and match.  Apply a wide variety of analytical tools to capacity decisions, including expected value and break-even analysis, decision trees, waiting line theory, and learning curves.

3 © 2008 Pearson Prentice Hall --- Introduction to Operations and Supply Chain Management, 2/e --- Bozarth and Handfield, ISBN: Chapter 8, Slide 3 Capacity Decisions Defining and measuring capacity Strategic versus tactical capacity Evaluating capacity alternatives Advanced perspectives –Theory of Constraints –Waiting lines –Learning curves

4 © 2008 Pearson Prentice Hall --- Introduction to Operations and Supply Chain Management, 2/e --- Bozarth and Handfield, ISBN: Chapter 8, Slide 4 Measure of an organization’s ability to provide goods or services Jiffy Lube  Oil changes per hour Law firm  Billable hours College  Student hours per semester Defining and Measuring Capacity

5 © 2008 Pearson Prentice Hall --- Introduction to Operations and Supply Chain Management, 2/e --- Bozarth and Handfield, ISBN: Chapter 8, Slide 5 Consider: Capacity for a PC Assembly Plant: (800 units/shift/line) × (% Good) × (# of lines) × (# of Shifts) 1 or 2 shifts? 2 or 3 lines? Employee training? Controllable Factors Uncontrollable Factors Supplier problems? 98% or 100% good? Late or on time?

6 © 2008 Pearson Prentice Hall --- Introduction to Operations and Supply Chain Management, 2/e --- Bozarth and Handfield, ISBN: Chapter 8, Slide 6 Strategic versus Tactical Capacity Strategic: –One or more years out –“Bricks & Mortar” –Future technologies Tactical: –One year or sooner –Workforce level, schedules, inventory, etc.

7 © 2008 Pearson Prentice Hall --- Introduction to Operations and Supply Chain Management, 2/e --- Bozarth and Handfield, ISBN: Chapter 8, Slide 7 Capacity Time Strategic Capacity Planning “Bricks & mortar” decisions High-level planning High risk Tactical Planning Workforce, inventory, subcontracting decisions Intermediate-level planning Moderate risk Planning & Control Limited ability to adjust capacity Detailed planning Lowest risk Days or weeks outMonths out Years out Capacity versus Time

8 © 2008 Pearson Prentice Hall --- Introduction to Operations and Supply Chain Management, 2/e --- Bozarth and Handfield, ISBN: Chapter 8, Slide 8 Capacity Strategies: When, How Much, and How? Leader Laggard Demand Lost Business Excess Capacity

9 © 2008 Pearson Prentice Hall --- Introduction to Operations and Supply Chain Management, 2/e --- Bozarth and Handfield, ISBN: Chapter 8, Slide 9 How? Make or Buy (e.g., subcontracting) One extreme: “Virtual” Business Walden Paddlers (Marketing) Hardigg Industries (Manufacturing) General Composites (Design) Independent Dealers (Direct Sales)

10 © 2008 Pearson Prentice Hall --- Introduction to Operations and Supply Chain Management, 2/e --- Bozarth and Handfield, ISBN: Chapter 8, Slide 10 Evaluating Capacity Alternatives Economies of scale (EOS) Expected value analysis (EVA) Decision Trees Break-even points (BEP)

11 © 2008 Pearson Prentice Hall --- Introduction to Operations and Supply Chain Management, 2/e --- Bozarth and Handfield, ISBN: Chapter 8, Slide 11 Economies of Scale Total Cost for Fictional Line: Fixed cost + (Variable unit cost)×(X) = $200,000 + $4X Cost per unit for X=1? X=10,000?

12 © 2008 Pearson Prentice Hall --- Introduction to Operations and Supply Chain Management, 2/e --- Bozarth and Handfield, ISBN: Chapter 8, Slide 12 Fixed & Unit Cost Scenarios

13 © 2008 Pearson Prentice Hall --- Introduction to Operations and Supply Chain Management, 2/e --- Bozarth and Handfield, ISBN: Chapter 8, Slide 13 Indifference Point Compares capacity alternatives — at what volume level do they cost the same? Suppose one option has zero fixed cost and $750 per unit cost; the other option has $5,000 fixed cost, but only $300 per unit cost. $0 + $750X = $5,000 + $300X What is the volume, X, at the indifference point?

14 Expected Value Analysis Forecasted demand or volume is uncertain, allows consideration of the variability in the data

15 © 2008 Pearson Prentice Hall --- Introduction to Operations and Supply Chain Management, 2/e --- Bozarth and Handfield, ISBN: Chapter 8, Slide 15 Data Requirements Capacity cost structure (alternatives?) Expected demand (multiple scenarios?) Product and service requirements (e.g. time standards) EVA

16 © 2008 Pearson Prentice Hall --- Introduction to Operations and Supply Chain Management, 2/e --- Bozarth and Handfield, ISBN: Chapter 8, Slide 16 Expected Value Analysis Pennington Cabinet Company 2000 jobs per year (20% likelihood) 5000 jobs per year (50%) 7000 jobs per year (30%) Each job = $1,200 revenue

17 © 2008 Pearson Prentice Hall --- Introduction to Operations and Supply Chain Management, 2/e --- Bozarth and Handfield, ISBN: Chapter 8, Slide 17 We Know: Average job requires: 2 hours of machine time 3-1/3 hours of assembly team time Machines and teams work 2000 hours per year Each machine and team has yearly fixed cost = $200K 3 different capacity scenarios (see next slide!)

18 © 2008 Pearson Prentice Hall --- Introduction to Operations and Supply Chain Management, 2/e --- Bozarth and Handfield, ISBN: Chapter 8, Slide 18 Effective Capacity What is the effective capacity of each capacity alternative? Number of Machines and Teams Number of Hours Available Each Year Maximum Jobs per Year MachinesTeamsMachinesTeamsMachinesTeams Current356,00010,0003,000 Expanded5910,00018,0005,0005,400 New Site71214,00024,0007,0007,200

19 © 2008 Pearson Prentice Hall --- Introduction to Operations and Supply Chain Management, 2/e --- Bozarth and Handfield, ISBN: Chapter 8, Slide 19 Alternate Demand Scenarios What is the expected contribution if demand = 5000 AND we decide to move to a new site? Why does revenue for current capacity max out at $3.6 million? Current LevelExpandedNew Site DemandRevenue Fixed ExpensesRevenue Fixed ExpensesRevenue Fixed Expenses 2,000$2,400,000$1,600,000$2,400,000$2,800,000$2,400,000$3,800,000 5,000$3,600,000$1,600,000$6,000,000$2,800,000$6,000,000$3,800,000 7,000$3,600,000$1,600,000$6,000,000$2,800,000$8,400,000$3,800,000

20 © 2008 Pearson Prentice Hall --- Introduction to Operations and Supply Chain Management, 2/e --- Bozarth and Handfield, ISBN: Chapter 8, Slide 20 Net Revenue Table DemandCurrentExpandedNew Site 3,000$800,000($400,000)($1,400,000) 5,000$2,000,000$3,200,000$2,200,000 7,000$2,000,000$3,200,000$4,600,000

21 © 2008 Pearson Prentice Hall --- Introduction to Operations and Supply Chain Management, 2/e --- Bozarth and Handfield, ISBN: Chapter 8, Slide 21 Expected Value of Each Capacity Alternative: Current capacity level (20%) × $800K +(50%) × $2000K +(30%) × $2000K =$1,760,000

22 © 2008 Pearson Prentice Hall --- Introduction to Operations and Supply Chain Management, 2/e --- Bozarth and Handfield, ISBN: Chapter 8, Slide 22 Expanded capacity level (20%) × – $400K +(50%) × $3200K + (30%) × $3200K =$2,480,000 Expected Value of Each Capacity Alternative:

23 © 2008 Pearson Prentice Hall --- Introduction to Operations and Supply Chain Management, 2/e --- Bozarth and Handfield, ISBN: Chapter 8, Slide 23 New Site capacity level (20%) × – $1400K +(50%) × $2200K +(30%) × $4600K =$2,200,000 Expected Value of Each Capacity Alternative:

24 © 2008 Pearson Prentice Hall --- Introduction to Operations and Supply Chain Management, 2/e --- Bozarth and Handfield, ISBN: Chapter 8, Slide 24 Conclusions for Pennington Which alternative would you choose if you wanted to minimize the worst possible outcome (Maximin)? Maximize the best possible outcome (Maximax)? Why is it important to know effective capacity? How could this help future capacity decisions?

25 Decision Trees Visual tool for evaluating choices using expected value analysis Allows use of different outcomes and different probabilities of success for each

26 © 2008 Pearson Prentice Hall --- Introduction to Operations and Supply Chain Management, 2/e --- Bozarth and Handfield, ISBN: Chapter 8, Slide 26 Decision Tree Requirements Decision points represented by –Choose the best input — the highest EVA, lowest cost, least risk, etc. Outcome points represented by –Summation of all inputs (outcomes) weighted by their respective probabilities. No choice can be made at these points Trees drawn from final decision to the outcomes affecting that decision, then on to lower level decisions that might affect the those outcomes, then the lower level outcomes affecting those lower level decisions, and so on

27 © 2008 Pearson Prentice Hall --- Introduction to Operations and Supply Chain Management, 2/e --- Bozarth and Handfield, ISBN: Chapter 8, Slide 27 Ellison Seafood Example Here the probabilities affecting the demand level are the same for the three options considered. But the decision tree does allow them to be different, can you think of situations where this might be true?

28 © 2008 Pearson Prentice Hall --- Introduction to Operations and Supply Chain Management, 2/e --- Bozarth and Handfield, ISBN: Chapter 8, Slide 28 Decision Tree Criteria Book example illustrates selecting highest revenue option. Other option choices can be on basis of: –Using total cost for outcomes (useful when selling price is not known) –Using estimated risk for outcomes –Outcomes reflecting a desired result (choose highest EVA) Can you think of an example? –Outcomes reflecting undesirable results (choose lowest EVA) Can you think of an example?

29 © 2008 Pearson Prentice Hall --- Introduction to Operations and Supply Chain Management, 2/e --- Bozarth and Handfield, ISBN: Chapter 8, Slide 29 Break-Even Point (BEP) Considers revenue and costs, at what volume level are they equal? Suppose each unit sells for $100, the fixed cost is $200,000 and the variable cost is $4 BEP  $100X = $200,000 + $4X What is the breakeven volume, X?

30 © 2008 Pearson Prentice Hall --- Introduction to Operations and Supply Chain Management, 2/e --- Bozarth and Handfield, ISBN: Chapter 8, Slide 30 Self Test EBB Industries must decide whether to invest in a new machine which has a yearly fixed cost of $40,000 and a variable cost of $50 per unit. What is the break even point (BEP) if each unit sells for $200? What is the expected value, given the following demand probabilities: 250 units (25%), 300 units (50%), 350 units (25%)

31 Advanced Perspectives Theory of Constraints Waiting lines Learning curves

32 Theory of Constraints Concept that the throughput of a supply chain is limited (constrained) by the process step with the lowest capacity. Sounds logical, but what does this mean for managing the other process steps?

33 © 2008 Pearson Prentice Hall --- Introduction to Operations and Supply Chain Management, 2/e --- Bozarth and Handfield, ISBN: Chapter 8, Slide 33 Theory of Constraints Pipeline analogy Which piece of the pipe is restricting the flow? Would making parts A or D bigger help?

34 © 2008 Pearson Prentice Hall --- Introduction to Operations and Supply Chain Management, 2/e --- Bozarth and Handfield, ISBN: Chapter 8, Slide 34 Dealing with a Constraint Identify the constraint Exploit the constraint  Keep it busy! Subordinate everything to the constraint  Make supporting it the overall priority Elevate the constraint  Try to increase its capacity — more hours, screen out defective parts from previous step, … Find the new constraint and repeat  As one step is removed as a constraint, a new one will emerge. Which piece of the pipe on the previous slide would be the new constraint if Part C was increased in diameter?

35 © 2008 Pearson Prentice Hall --- Introduction to Operations and Supply Chain Management, 2/e --- Bozarth and Handfield, ISBN: Chapter 8, Slide 35 Waiting Lines Waiting lines and services –Waiting and customer satisfaction –Factors affecting satisfaction Waiting Line Theory –Terminology and assumptions – Illustrative example

36 © 2008 Pearson Prentice Hall --- Introduction to Operations and Supply Chain Management, 2/e --- Bozarth and Handfield, ISBN: Chapter 8, Slide 36 Waiting at Outback Steakhouse... Waiting to get food... Waiting to pay bill... Leaving restaurant Waiting outside or in bar

37 © 2008 Pearson Prentice Hall --- Introduction to Operations and Supply Chain Management, 2/e --- Bozarth and Handfield, ISBN: Chapter 8, Slide 37 Key Points Waiting time DECREASES value-added experience On the other hand, adding serving capacity INCREASES costs Businesses must have a way to analyze the impact of capacity decisions in environments where waiting occurs

38 © 2008 Pearson Prentice Hall --- Introduction to Operations and Supply Chain Management, 2/e --- Bozarth and Handfield, ISBN: Chapter 8, Slide 38 Waiting and Customer Satisfaction Cost of waiting Cost of service COST Waiting time Lost customers

39 © 2008 Pearson Prentice Hall --- Introduction to Operations and Supply Chain Management, 2/e --- Bozarth and Handfield, ISBN: Chapter 8, Slide 39 Cost of Waiting = f(Satisfaction) Factors Affecting Satisfaction 1.Firm-related factors 2.Customer-related factors

40 © 2008 Pearson Prentice Hall --- Introduction to Operations and Supply Chain Management, 2/e --- Bozarth and Handfield, ISBN: Chapter 8, Slide 40 Firm-Related Factors “Unfair” versus “fair” waits Uncomfortable versus comfortable waits Initial versus subsequent waits Capacity decisions

41 © 2008 Pearson Prentice Hall --- Introduction to Operations and Supply Chain Management, 2/e --- Bozarth and Handfield, ISBN: Chapter 8, Slide 41 Waiting Line (Queuing) Theory Application of statistics to allow us to perform a detailed analysis of system –Utilization levels, line lengths, etc. Terminology and assumptions

42 © 2008 Pearson Prentice Hall --- Introduction to Operations and Supply Chain Management, 2/e --- Bozarth and Handfield, ISBN: Chapter 8, Slide 42 Terminology and Assumptions I

43 © 2008 Pearson Prentice Hall --- Introduction to Operations and Supply Chain Management, 2/e --- Bozarth and Handfield, ISBN: Chapter 8, Slide 43 Terminology and Assumptions II Single-Channel Single-Phase Multiple-Channel Single-Phase

44 © 2008 Pearson Prentice Hall --- Introduction to Operations and Supply Chain Management, 2/e --- Bozarth and Handfield, ISBN: Chapter 8, Slide 44 Terminology and Assumptions III Complex service environment... How would you describe this?

45 © 2008 Pearson Prentice Hall --- Introduction to Operations and Supply Chain Management, 2/e --- Bozarth and Handfield, ISBN: Chapter 8, Slide 45 Terminology and Assumptions IV Population: Infinite or Finite Arrival rates:Random or constant rate –Random rates typically defined by Poisson distribution for infinite population Service Rates: Random or constant –Random service rates typically described by exponential distribution Priority rules (aka “Queue Discipline”) Permissible queue length

46 © 2008 Pearson Prentice Hall --- Introduction to Operations and Supply Chain Management, 2/e --- Bozarth and Handfield, ISBN: Chapter 8, Slide 46 Example A single drive-in window for Bank Arrival rate –15 per hour, on average Service rate –20 per hour, on average How many channels? Phases? What kinds of questions might we have?

47 © 2008 Pearson Prentice Hall --- Introduction to Operations and Supply Chain Management, 2/e --- Bozarth and Handfield, ISBN: Chapter 8, Slide 47 Drive-In Bank = arrival rate = 15 cars per hour  = service rate =20 cars per hour Average utilization of the system:  =  = 0.75

48 © 2008 Pearson Prentice Hall --- Introduction to Operations and Supply Chain Management, 2/e --- Bozarth and Handfield, ISBN: Chapter 8, Slide 48 Drive-In Bank Probability of n arrivals during period T is: e.g., probability of only 4 arrivals during a 45-minute period is:

49 © 2008 Pearson Prentice Hall --- Introduction to Operations and Supply Chain Management, 2/e --- Bozarth and Handfield, ISBN: Chapter 8, Slide 49 Drive-In Bank Average number of cars in the system: (waiting plus being served)

50 © 2008 Pearson Prentice Hall --- Introduction to Operations and Supply Chain Management, 2/e --- Bozarth and Handfield, ISBN: Chapter 8, Slide 50 Drive-In Bank Average number of cars waiting:

51 © 2008 Pearson Prentice Hall --- Introduction to Operations and Supply Chain Management, 2/e --- Bozarth and Handfield, ISBN: Chapter 8, Slide 51 Drive-In Bank Average time spent in the system: (waiting plus being served) (How do we know the answer is in hours?)

52 © 2008 Pearson Prentice Hall --- Introduction to Operations and Supply Chain Management, 2/e --- Bozarth and Handfield, ISBN: Chapter 8, Slide 52 Drive-In Bank Average time spent in the line: (How do we know the answer is in hours?)

53 Question? What happens as the arrival rate approaches the service rate? Suppose is now 19 cars per hour

54 © 2008 Pearson Prentice Hall --- Introduction to Operations and Supply Chain Management, 2/e --- Bozarth and Handfield, ISBN: Chapter 8, Slide 54 One Answer: Average number of cars waiting: Implications? What are we assuming here?

55 © 2008 Pearson Prentice Hall --- Introduction to Operations and Supply Chain Management, 2/e --- Bozarth and Handfield, ISBN: Chapter 8, Slide 55 Other Types of Systems (Discussed in the supplement to Chapter 8) Single-channel, single-phase with constant service time –Example: Automatic car wash Multiple-channel, multiple-phase (hospital) –Usually best handled using simulation analysis

56 © 2008 Pearson Prentice Hall --- Introduction to Operations and Supply Chain Management, 2/e --- Bozarth and Handfield, ISBN: Chapter 8, Slide 56 Self Test I Look back at the drive-in window example. How can we have an average line length > 1 while the average number of cars being served is < 1? Similarly, what happens as the arrival rate approaches the service rate? Suppose the teller at the drive-in window is given training and can now handle 25 cars an hour (a 25% increase in service rate). What happens to the average length of the line?

57 © 2008 Pearson Prentice Hall --- Introduction to Operations and Supply Chain Management, 2/e --- Bozarth and Handfield, ISBN: Chapter 8, Slide 57 Self Test II Look back at the Outback Steakhouse example. What kind of queuing system is it?

58 Question? How can capacity change, even when we do not hire new people or put in new equipment?

59 © 2008 Pearson Prentice Hall --- Introduction to Operations and Supply Chain Management, 2/e --- Bozarth and Handfield, ISBN: Chapter 8, Slide 59 Learning Curves Recognize that people (and often equipment) become more productive over time due to learning. First observed in aircraft production during World War II Getting more emphasis as companies outsource more activities

60 © 2008 Pearson Prentice Hall --- Introduction to Operations and Supply Chain Management, 2/e --- Bozarth and Handfield, ISBN: Chapter 8, Slide 60 A Formal Definition For every doubling of cumulative output, there will be a set percentage improvement in time per unit or some other measure of input Output Time per unit 10 hrs. 8 hrs. 6.4 hrs hrs hrs. 80% learning curve - Where does the name come from?

61 © 2008 Pearson Prentice Hall --- Introduction to Operations and Supply Chain Management, 2/e --- Bozarth and Handfield, ISBN: Chapter 8, Slide 61 A Formal Definition (cont’d) Where:T n = time for the nth unit T 1 = time for the first unit b = ln(learning percent) / ln2

62 © 2008 Pearson Prentice Hall --- Introduction to Operations and Supply Chain Management, 2/e --- Bozarth and Handfield, ISBN: Chapter 8, Slide 62 Example Reservation clerk at Delta Airlines First call (while training) takes 8 minutes Second call takes 6 minutes What is the learning rate? How long would you expect the 4th call to take? The 16th? The 32nd?

63 © 2008 Pearson Prentice Hall --- Introduction to Operations and Supply Chain Management, 2/e --- Bozarth and Handfield, ISBN: Chapter 8, Slide 63 Key Points Quick improvements early on, followed by more and more gradual improvements The lower the percentage, the steeper the learning curve Practically speaking, there is a floor Estimates of effective capacity must consider learning effects!

64 Another Question... How could learning curves be used in long-term purchasing contracts?

65 © 2008 Pearson Prentice Hall --- Introduction to Operations and Supply Chain Management, 2/e --- Bozarth and Handfield, ISBN: Chapter 8, Slide 65 Johnston Controls I Johnston Controls won a contract to produce 2 prototype units for a new type of computer. First unit took 5,000 hrs. to produce and $250K of materials Second unit took 3,500 hrs. to produce and $200K of materials Labor costs are $30/hour

66 © 2008 Pearson Prentice Hall --- Introduction to Operations and Supply Chain Management, 2/e --- Bozarth and Handfield, ISBN: Chapter 8, Slide 66 Johnston Controls II The customer has asked Johnston Controls to prepare a bid for an additional 10 units. What are Johnston’s expected costs?

67 © 2008 Pearson Prentice Hall --- Introduction to Operations and Supply Chain Management, 2/e --- Bozarth and Handfield, ISBN: Chapter 8, Slide 67 Johnston Controls III Labor learning rate: 3500 hours / 5000 hours = 70% Materials learning rate: $200K / $250K = 80%

68 © 2008 Pearson Prentice Hall --- Introduction to Operations and Supply Chain Management, 2/e --- Bozarth and Handfield, ISBN: Chapter 8, Slide 68 Johnston Controls IV “Additional 10 units” means the third through twelfth units. Total labor for units 3 through 12: =5,000 hours × (5.501 – 1.7) = 19,005 hrs is sum of n b for 12 units 1.7 is the sum of n b for the first two units

69 © 2008 Pearson Prentice Hall --- Introduction to Operations and Supply Chain Management, 2/e --- Bozarth and Handfield, ISBN: Chapter 8, Slide 69 Johnston Controls V Total material for units 3 through 12: = $250,000 × (7.227 – 1.8) = $1,356,750

70 © 2008 Pearson Prentice Hall --- Introduction to Operations and Supply Chain Management, 2/e --- Bozarth and Handfield, ISBN: Chapter 8, Slide 70 Johnston Controls VI Total cost for “additional 10 units”: = $30 × (19,005 hours) + $1,356,750 = $1,926,900 What if there is a significant delay before the second contract?

71 © 2008 Pearson Prentice Hall --- Introduction to Operations and Supply Chain Management, 2/e --- Bozarth and Handfield, ISBN: Chapter 8, Slide 71 Self-Test Assume that there WILL BE a significant delay before Johnston Controls makes the next 10 units. Assuming that Johnston has to “start over” with regard to learning, estimate total cost for these additional 10 units.

72 Case Study in Managing Capacity Forster’s Market


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