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Ch42-I044963.fm Page 205 Tuesday, August 1, 2006 3:57 PM
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equipment according to the priority.
STEP5 Termination of reallocation process: The reallocation process is terminated, just before the load of the
selected machining equipment crosses the average balanced load (ABL).
After STEP 1 to STEP 5, some of the machining features are loaded to the selected machining equipment. The
machining equipment, which carries out these machining features, is fixed. On the other hand, the remaining
machining features shall be loaded to the machining equipment except the selected one. The procedures in the
next section are applied for selecting the suitable machining equipment for the remaining machining features.

Selection of suitable machining equipment

Figure 2 shows an example of the status of the alternative machining equipment of the machining features of the
job holon i, after the reallocation process is completed. In this case, the machining equipment ME2 is reallocated
and balanced, therefore, the machining feature MFn is fixed to ME2, and the other alternative machining
equipment for MFn are deleted. As regards to other machining features, if they have ME2 as the alternative
machining equipment, ME2 is deleted from the alternative.

° °
P i 1 2 °° ° ° N
Ma c h i n i n g fe a t u re s M F ij
MF 1j
° ° ° ° ° °
MF 11 MF 12
ME 1 ME 1 ME 1 ME 1 ME 1
ME 2 ME 2 ME 2 ME 2 ME 2
ME 3 ME 3 ME 3 ME 3
ME 4 ME 4 M a c h in in g eq u ip m e n t s ME
ME 5 a

Figure 2 : Modified process plans with alternative machine equipment

Following this, all the job holons regenerate new sequences of the machining equipment under the constraints
determined in the load balancing process.

CASE STUDY

The algorithm has been constructed based on the load balancing method and the dynamic programming method
and a prototype of the process planning and scheduling system has been implemented using C++ language. One
of the case result is summarized in Figures. 3 and 4, which show that the make span has been reduced from
28561.5 sec. before load balancing to 19335.7 sec. after load balancing. Balancing of the machining equipment is
carried out in the sequence of most busy machining equipment to the least busy machining equipment, and the
balancing sequence of the machining equipment is MT12, MT3, MT6, MT17, MT14, MT9 and finally MT15, in
this case.