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Aggregat planning stevenson
 

Aggregat planning stevenson

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    Aggregat planning stevenson Aggregat planning stevenson Presentation Transcript

    • William J. Stevenson Operations Management 8 th edition
    • CHAPTER 12 Aggregate Planning McGraw-Hill/Irwin Operations Management, Eighth Edition, by William J. Stevenson Copyright © 2005 by The McGraw-Hill Companies, Inc. All rights reserved.
    • Planning Horizon
      • Aggregate planning : Intermediate-range capacity planning, usually covering 2 to 12 months.
      Short range Intermediate range Long range Now 2 months 1 Year
      • Short-range plans (Detailed plans)
        • Machine loading
        • Job assignments
      • Intermediate plans (General levels)
        • Employment
        • Output
      • Long-range plans
        • Long term capacity
        • Location / layout
      Overview of Planning Levels
    • Planning Sequence Figure 12.1 Business Plan Establishes operations and capacity strategies Aggregate plan Establishes operations capacity Master schedule Establishes schedules for specific products Corporate strategies and policies Economic, competitive, and political conditions Aggregate demand forecasts
      • Resources
        • Workforce
        • Facilities
      • Demand forecast
      • Policies
        • Subcontracting
        • Overtime
        • Inventory levels
        • Back orders
      • Costs
        • Inventory carrying
        • Back orders
        • Hiring/firing
        • Overtime
        • Inventory changes
        • subcontracting
      Aggregate Planning Inputs
      • Total cost of a plan
      • Projected levels of inventory
        • Inventory
        • Output
        • Employment
        • Subcontracting
        • Backordering
      Aggregate Planning Outputs
    • Aggregate Planning Strategies
      • Proactive
        • Alter demand to match capacity
      • Reactive
        • Alter capacity to match demand
      • Mixed
        • Some of each
      • Pricing
      • Promotion
      • Back orders
      • New demand
      Demand Options
      • Hire and layoff workers
      • Overtime/slack time
      • Part-time workers
      • Inventories
      • Subcontracting
      Capacity Options
    • Aggregate Planning Strategies
      • Maintain a level workforce
      • Maintain a steady output rate
      • Match demand period by period
      • Use a combination of decision variables
    • Basic Strategies
      • Level capacity strategy:
        • Maintaining a steady rate of regular-time output while meeting variations in demand by a combination of options.
      • Chase demand strategy:
        • Matching capacity to demand; the planned output for a period is set at the expected demand for that period.
    • Chase Approach
      • Advantages
        • Investment in inventory is low
        • Labor utilization in high
      • Disadvantages
        • The cost of adjusting output rates and/or workforce levels
    • Level Approach
      • Advantages
        • Stable output rates and workforce
      • Disadvantages
        • Greater inventory costs
        • Increased overtime and idle time
        • Resource utilizations vary over time
      • Determine demand for each period
      • Determine capacities for each period
      • Identify policies that are pertinent
      • Determine units costs
      • Develop alternative plans and costs
      • Select the best plan that satisfies objectives. Otherwise return to step 5.
      Techniques for Aggregate Planning
    • Cumulative Graph Figure 12.3 1 2 3 4 5 6 7 8 9 10 Cumulative production Cumulative demand Cumulative output/demand
    • Average Inventory Average inventory Beginning Inventory + Ending Inventory 2 =
    • Mathematical Techniques
      • Linear programming : Methods for obtaining optimal solutions to problems involving allocation of scarce resources in terms of cost minimization.
      • Linear decision rule : Optimizing technique that seeks to minimize combined costs, using a set of cost-approximating functions to obtain a single quadratic equation.
    • Summary of Planning Techniques Table 12.7
      • Services occur when they are rendered
      • Demand for service can be difficult to predict
      • Capacity availability can be difficult to predict
      • Labor flexibility can be an advantage in services
      Aggregate Planning in Services
    • Aggregate Plan to Master Schedule Figure 12.4 Aggregate Planning Disaggregation Master Schedule
      • Master schedule : The result of disaggregating an aggregate plan; shows quantity and timing of specific end items for a scheduled horizon.
      • Rough-cut capacity planning : Approximate balancing of capacity and demand to test the feasibility of a master schedule.
      Disaggregating the Aggregate Plan
    • Master Scheduling
      • Master schedule
        • Determines quantities needed to meet demand
        • Interfaces with
          • Marketing
          • Capacity planning
          • Production planning
          • Distribution planning
    • Master Scheduler
      • Evaluates impact of new orders
      • Provides delivery dates for orders
      • Deals with problems
        • Production delays
        • Revising master schedule
        • Insufficient capacity
    • Master Scheduling Process Figure 12.6 Master Scheduling Beginning inventory Forecast Customer orders Inputs Outputs Projected inventory Master production schedule Uncommitted inventory
    • Projected On-hand Inventory Projected on-hand inventory Inventory from previous week Current week’s requirements - =
    • Projected On-hand Inventory Figure 12.8 Beginning Inventory Customer orders are larger than forecast in week 1 Forecast is larger than Customer orders in week 2 Forecast is larger than Customer orders in week 3
    • Time Fences in MPS Period “ frozen” (firm or fixed) “ slushy” somewhat firm “ liquid” (open) Figure 12.12 9 8 7 6 5 4 3 2 1
    • Solved Problems: Problem 1