Page 275 - Orlicky's Material Requirements Planning

254 PART 3 Managing with the MRP System

The instrument of priority control is a dispatch list or departmental schedule, typi-
cally generated daily or weekly (the latter is of lower effectiveness), that may be in the
form of a printed report, cards, or individual work-sequence messages or conveyed
through a visual-display device. In any of these cases, the essence of the dispatch list is a
ranking, by relative priority, of jobs (material that an operation is to be performed on)
physically present in a manufacturing department and sometimes of jobs about to arrive
in the department. A sample dispatch list is shown in Figure 13-2.
The sequence of work established by the dispatch list is based on operation priori-
ties, which, in turn, are derived from order priorities. As order due dates are being
revised via the MRP system, operation priorities must be reestablished accordingly. They
may be expressed by means of operation start dates (as in the Figure 13-2 example) or
operation finish dates, and if so, the affected orders first must be rescheduled by the oper-
ations scheduling system. Alternatively, the priorities can be expressed by means of one
of a variety of priority ratios that are geared to order due dates.
A priority control system (i.e., dispatching or job sequencing) and its related instru-
ments exist in every manufacturing plant in some form. Without input from an MRP sys-
tem, however, a priority control system cannot function very effectively because the
information tends to be out of date, invalid, and untrue. Shop personnel do not and can-
not rely on this information, and so the system must be supplemented by expediting of
shortage lists. The shortage lists, incomplete as they usually are, then reflect the true pri-
orities.

FIGURE 13-2
Daily dispatch list.

Dispatch List
Department: No. 12 Turret lathes Date: March 15
Jobs in department
Order # Part # Quantity Operation # Start Date Std. Hours Remarks
5987 B-3344 50 30 3/7 3.2 Tooling in repair
5968 B-4567 100 25 3/12 6.6 Eng. hold
5988 F-8978 30 42 3/14 4.8
5696 12-1133 300 20 3/15 14.5
5866 A-4675 60 20 3/15 7.0
5996 A-9845 200 30 3/16 6.2
5876 F-4089 25 40 4/10 5.4

Jobs scheduled to arrive this date
6078 A-3855 160 30 3/14 6.5 In dept. 15
6001 D-8000 300 65 3/16 9.8 In dept. 08