It is hypothesised that the self-balancing nature inherent in the BB methodology will allow
management to find an ‘appropriate’ economic balance between machine coverage and
mechanic utilisation. Therefore, two general approaches will be undertaken in the
postulation of the MBS rule-based structure. One approach will be to assign the highest
skilled mechanic in the highest mechanic category to a machine requiring service, or
replace another, lower skilled, mechanic that is servicing a machine. This should increase
the utilisation of the highest paid employees, with the goal of increasing the overall
efficiency and cost of the corrective maintenance operation by potentially removing lower
paid employees from the system. This policy is related to the BB rule that gives preemptive
rights to the faster, downstream operators. It should be noted that the approach
of assigning and replacing with respect to the lowest feasible category of mechanic is a
concept left for future investigation.
We hypothesise that while the overall efficiency of the corrective maintenance system
may not be as high as in the aforementioned approach, the system could maintain the most
capable mechanics available and therefore, possibly provide greater assurance of machine
coverage which can be a critical consideration to the appeal of this methodology in
industry. This is left as an area for future investigation. The three dynamic work allocation
rules and the one pre-emption rule that constitute the MBS are provided below after their
respective premises are discussed and rationalised.
When a machine goes down, what mechanic category (that is capable of servicing that
machine) should be assigned?
Assigning the highest mechanic category first may lead to the maximisation of the
utilisation of the highest paid personnel. On the other hand, assigning the lowest mechanic
category to service a machine may allow the system to increase the probability of machine
coverage by sparing the higher (and more capable) mechanic categories to service the
machines that may fail next. This increment in machine coverage may promote the
maximisation of machine availability by having a capable mechanic available to service a
particular machine type albeit at the expense of mechanic utilisation.
Rule 1. When a machine breaks down, first assign the highest mechanic category.
We opt for assigning the highest mechanic category first with the assumption that this
category contains the costliest personnel. In addition, the assignment of available
mechanics from the chosen mechanic category is another key design issue that can directly
influence mechanic utilisation. For instance, assigning the best available mechanic in the
chosen category could increase the utilisation of the mechanics by keeping the best
mechanics busy within a mechanic category. This will permit management in a
quantitative manner to determine the utilisation of lower ranked mechanics in a mechanic
category, and if such utilisation is low, then this can be an indicator that the system may
not need that many mechanics in that category, and thus a reduction in the manpower
levels may be feasible.
In the case that there are no unassigned mechanics in the most appropriate category as per
Rule 1, should the best available mechanic of the next higher or next lower mechanic category
be chosen?
Assigning the next lower, most appropriate and available mechanic category may
contribute to the maximisation of the highest paid personnel. On the other hand, assigning
the next higher available mechanic category may maximise, as in Rule 1, the availability of
machines by assigning the lowest mechanic categories available, which results in sparing
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