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Theory of Constraints. Short-term Capacity Optimization. Theory of Constraints. Significance of bottlenecks Maximum speed of the process is the speed of the slowest operation Any improvements will be wasted unless the bottleneck is relieved

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Theory of constraints

Theory of Constraints

Short-term Capacity Optimization


Theory of constraints1
Theory of Constraints

  • Significance of bottlenecks

    • Maximum speed of the process is the speed of the slowest operation

    • Any improvements will be wasted unless the bottleneck is relieved

      • Bottlenecks must be identified and improved if the process is to be improved


Theory of constraints2
Theory of Constraints

  • Purpose is to identify bottlenecks or other constraints and exploit them to the extent possible

    • Identification of constraints allows management to take action to alleviate the constraint in the future

      • Reduce cycle time

        • Time from receipt of customer order to shipment

      • Improve manufacturing cycle efficiency (MCE)

        • Processing time / total cycle time


Theory of constraints3
Theory of Constraints

  • Assumes current constraints cannot be changed in the short-run

    • What should be produced now, with current resources, to maximize profits?

      • Question cannot be answered by traditional accounting methods


Theory of constraints4
Theory of Constraints

  • Management tool, not an accounting tool

    • Not used to determine inventory values

    • Not used to allocate overhead to inventory

    • Does not comply with GAAP

  • Does indicate how to use available resources most effectively


The need for toc
The Need for TOC

  • Standard costing

    • Can promote undesirable behavior

      • Work to keep people busy

        • Local optimization

        • Inventory is produced regardless of need

    • Does indicate what it should cost to produce a product


The need for toc1
The Need for TOC

  • Does not indicate which products will maximize profits given the constraints

    • Doesn’t take constraints into account

    • Does not consider the demands each item places on limited resources


The need for toc2
The Need for TOC

  • Absorption costing

    • Can promotes undesirable behavior

      • Production costs are assets until sold

        • Accumulation of inventory keeps costs off the income statement

        • Illusion of profitability

    • Does indicate what it costs to produce a product


The need for toc3
The Need for TOC

  • Does not indicate which products will maximize profits given the constraints

    • Doesn’t take constraints into account

    • Absorption cost does not consider the demands each item places on limited resources


The need for toc4
The Need for TOC

  • Variable (direct) costing

    • Identifies the incremental costs of producing a product

      • Identifies product that provides the greatest contribution margin, or contribution margin per unit of constrained resource

        • Cannot deal with more than one constraining resource at a time


The need for toc5
The Need for TOC

  • Traditional definition of variable cost doesn’t hold in the short-run

    • Labor, variable overhead aren’t really variable on a day-to-day basis

  • Some costs are truly variable in the short-run

    • Material, commissions, delivery costs, out-of-pocket selling costs, etc.

      • Each additional unit produced or sold causes more of the cost to be incurred


The need for toc6
The Need for TOC

  • Theory of Constraints

    • Uses linear programming to determine best use of limited resources

      • Indicates what should be produced and in what quantities


Theory of constraints5
Theory of Constraints

  • Constraining resource must be maximized

    • All other operations must be geared toward this goal

      • May require suboptimization in other areas

        • Upstream operations must provide only what the constraint can handle

        • Downstream operations will only receive what the constraint can put out


Theory of constraints6
Theory of Constraints

  • Constraint must be kept operating at its full capacity

    • If not, the entire process slows further

  • Focus is on maximizing throughput

    • Sales – totally variable costs

    • All other costs treated as fixed operational expenses

      • Cannot vary much in the short-run


  • Theory of constraints7
    Theory of Constraints

    • Based on the concepts of drum, buffer and ropes

      • Drum

        • Output of the constraint is the drumbeat

          • Sets the tempo for other operations

          • Tells upstream operations what to produce

          • Tells downstream operations what to expect


    Theory of constraints8
    Theory of Constraints

    • Buffer

      • Stockpile of work in process in front of constraint

        • Precaution to keep constraint running if upstream operations are interrupted

    • Rope

      • Sequence of processes prior to and including the constraint

        • Want to “pull” the rope at the maximum speed

          • Speed of the constraint


    Steps in the toc process

    Internal

    Process constraints

    Machine time, etc.

    Policy constraints

    No overtime, etc.

    External

    Material constraints

    Insufficient materials

    Market constraints

    Insufficient demand

    Steps in the TOC Process

    • Identify the system constraints

    • How is a constraint identified?


    Steps in the toc process1
    Steps in the TOC Process

    • Decide how to exploit the constraint

      • Produce the most profitable product mix

      • Want it working at 100%

        • How much of a buffer?

          • Holding costs

            • Including risk, quality costs

          • Stock-out costs


    Steps in the toc process2
    Steps in the TOC Process

    • Subordinate everything else to the preceding decision

      • Plan production to keep constraint working at 100%

      • May need to change performance measures to conform upstream activities to the “rope” speed




    Steps in the toc process5
    Steps in the TOC Process

    • Alleviate the constraint

      • Determine how to increase its capacity

    • Repeat the process

      • Always a new constraint


    Evaluation of toc
    Evaluation of TOC

    • Advantages

      • Improves capacity decisions in the short-run

      • Avoids build up of inventory

      • Aids in process understanding

      • Avoids local optimization

      • Improves communication between departments


    Evaluation of toc1
    Evaluation of TOC

    • Disadvantages

      • Negative impact on non-constrained areas

        • Diverts attention from other areas that may be the next constraint

        • Temptation to reduce capacity


    Evaluation of toc2
    Evaluation of TOC

    • Ignores long-run considerations

      • Introduction of new products

      • Continuous improvement in non-constrained areas

    • May lead organization away from strategy

    • Not a substitute for other accounting methods


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