Thursday, December 13, 2007

Priority Rules in Dispatching Jobs


There are four different sets of guidelines that a business will commonly use in determining the sequence of order completion. These rules are:
  • FCFS: First Come, First Served
  • SPT: Shortest Processing Time
  • EDD: Earliest Due Date
  • LPT: Longest Processing Time

  • These guidelines or rules can be followed by the service industry, manufacturing industry, and retail industry. Actually, they really can be applied in one way or another to practically any business.

    FCFS:
    First Come, First Served
    is the idea that the first job to come in, is the first job to be completed. This can be a costly procedure to follow for some businesses, such as those in the manufacturing industry, where efficiency in time and energy are of high importance. However, FCFS is more suited to a retail industry. Customers waiting in line do not like it when others get to jump ahead of them. Diners at a restaurant do not like to be ignored because their order is time consuming. Therefore, FCFS may sometimes be better suited to the retail industry since it appears fair to customers.(Keeping in mind that there are always exceptions).

    SPT:
    Shortest Processing Time
    may be the most efficient of all at completing the most jobs in the shortest period of time. This could be of an advantage to businesses and plants with few long term projects. However, if there are long term projects, watch out for missed deadlines. These projects may get bumped back to complete the shorter term projects.

    EDD:
    Earliest Due Date
    will minimize your average lateness. If there are fines or contractual penalties attached to project deadlines, this is the plan for you. This may not be the most efficient way for a firm to use its resources, but projects are more likely to come out on time this way.

    LPT:
    Longest Processing Time
    is a ridiculous way to run a business. However, it may come in handy to create a "worst case scenario" to plan against. LPT could be useful for that.

    These are 4 basic guidelines that businesses can follow. There are others to be aware of including the Critical Ratio and Johnson's Rule, but I will leave those for a future discussion. Knowing how to sequence jobs is an important short-term timeframe management tool. It ensures that a business will run more efficiently and hopefully be successful in meeting priority orders.

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