Bottleneck management

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Last update: March 27th, 2006
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Bottleneck (Reminder)

  • A bottleneck resource is a resource which average capacity is just equal to or below market needs. Conversely, resources having average capacities exceeding the market needs, are non-bottlenecks.

  • Rule nº2 of theory of constraints quotes: "Any time lost on a bottleneck is wasted for the whole system". In consequence, all attention must be paid to bottlenecks, deserving favored care.


    Managing bottleneck

    Such a precious resource like a bottleneck must have its activity maximized, because it determines directly the results for the whole process. This maximization can be achieved through:

    • Production scheduling, trying to reduce number of setups and changeovers, in the acceptable limits of customer requirements
    • Quick changeovers through SMED (Single Minute Exchange of Die) approach
    • Reliability and availability with preventive, planned and autonomous maintenance, all parts of TPM, Total Productive Maintenance

    TPM gives also a precious indicator for performance assessment, follow-up and improvement of this resource, namely OEE, Overall Equipment Effectiveness.


    Internal logistics

    The bottleneck is the key part of a process, which performance is directly related to the bottleneck's. Apart from bottleneck's performance itself, the links to up and down stream resources must be managed as well, because linked non-bottlenecks resourecs can affect the bottleneck.

    The ideal situation is to have the bottleneck always fed, protected from shortages with a buffer inventory in front of it.

     

     

    Upstream links

    The most embarassing situation would be a bottleneck stopped because of feeding shortage while upstream resources all have excess capacities.

      The ToC rules teach us the time wasted on a bottleneck can never be recovered, for the simple reason that if any spare time would remain, by overtime work or extra shifts, the bottleneck would not really be a bottleneck!

    Downstream link

    If prevention of feeding shortage is usually well done, the downstream link is sometimes neglected.

    In such a case, an other embarassing situation occurs; bottleneck is availlable and fed, but cannot work because blocked by saturation! This situation is even more embarassing that downstream process has excess capacity.

  • Read on HC online

    Batch size reduction
    ABC method for warehouse layout
    Scheduling is like playing Tetris !

     

    Author, Chris HOHMANN, is manager and consultant in an international consulting firm.

    His fields are industrial and logistics performance.

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    Such blocking situations related to downstream links can be found in automated conveyor links between machines, where safety devices stop the machines if unloading or transportation isn't possible.


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