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Ch 16 - Scheduling

  1. Introduction     (p719)
    1. Def - Scheduling - specifying when labor, material, equipment, and facilities are needed to produce a product.
    2. Scheduling for an intermittent process (job shop) is more difficult than for a repetitive or continuous process, because of the large variety of different products.
  2. Job Shop Scheduling      (p720)
    1. Typically performed by a production control department
    2. Primary Activities
      1. *Loading - assigning jobs to work centers
        1. Check availability of labor, material, and equipment
        2. Fine tune the MRP/CRP schedule.
      2. Sequencing - specifying the order in which jobs should be done at each work center.
      3. Monitoring - maintaining progress reports and determining corrective action when necessary.
  3. Sequencing (Jobs in Work Centers)       (p722)
    1. *Priority rules - do not give optimal solution   (For examples, see Example 16.2, p724)
      1. FCFS - First Come, First Served
      2. DDATE - Earliest Due Date
      3. SPT - Shortest Processing Time
      4. LPT - Longest Processing Time
      5. Smallest SLACK = (Due date - Today's date) - Work time remaining
      6. Smallest Critical Ratio = (Due date - Today's date) / Work time remaining
    2. *Johnson’s Rule    (p726)
      1. Optimization method to minimize total processing time for sequencing n jobs thru 2 work centers.
      2. Procedure
        1. Select job with shortest time
        2. If shortest time corresponds to work center 1
              then place corresponding job as early as possible
              else place corresponding job as late as possible.
        3. Eliminate that job and repeat steps a and b with remaining jobs.
      3. Example 16.3 - Job shop with five jobs that must be sanded first in work center 1 and painted in work center 2   (p727).
        Processing Time for Jobs (in hours)

        Job

        Work Center
        1 2
        A
        B
        C
        D
        E

         6
        11
         7
         9
         5

         8
         6
         3
         7
        10
        1. Optimal sequence is E, A, D, B, C. (See page 727 for graph of job flow.)
                       Job Sequence
    First  Second Third  Fourth  Fifth 
      -
      E
      E
      E
      E    		   -
      -
      A
      A
      A    		   -
      -
      -
      -
      D    		   -
      -
      -
      B
      B    		   C
      C
      C
      C
      C

                                      Do assigned HW - Problem 16-17.
                                                                     (This page was last edited on August 16, 2006 .)