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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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