Load - capacity Balancing check
Checking the balance between workload and
resource capacity means to verify if a task, project or production of a
batch is feasible of not. Therefore, it is necessary to compare resource
capacity required vs avaible resources capacities in the
considered
time span.
Load - capacity Balancing check
can also mean the decision process which will discard all or part of the job
exceeding available capacity, or conversely, decide to increase the actual
capacity to fit the requirement.
Work Load:
job volume x necessary time to process it (+ eventually setup time if
resource cannot be used meanwhile)
Capacity: available time to process job x
number of similar resources
LET's play !
Load - capacity Balancing check
Assume a resource whith a capacity = 25 units, figured by the 5X5 grid on the left.
(imagine five days a week with five time period each)
Load - capacity Balancing check is to
verify that the whole workload, beeing the sum of 6 production orders, is less or
at least equal to 25 units.
The workload,
is figured with 6 production order (shapes1 to 6).
Your assignement: check load - capacity, can we process the
whole batch with actual resource?
Answer
Scheduling
Scheduling is to find an arrangement allowing
sequential task processing, so that the entire project or production is achieved
on time.
With the same example as above, find a
scheduling (placement of orders 1 to 6) so that production can be done within 25
available time units of our grid.
Several solutions exist.
Click here for proposed solution .
Constraint scheduling
It happens scheduling (arrangements) are limited
by constraints, for example the batch figured by the
blue part
n°2 cannot be set just before or just after
red batch (part n°1).
In such a case,
previous solution
doesn't fit anymore. Find a new scheduling
fitting the double constraint:
Click here for proposed solution 2 .
CONCLUSION
Checking the balance between load and capacity by comparing the sum of required
and available time is too coarse. It can be misleading as scheduling constraints
are not taken into account.
Last example
 Here
is an example where available capacity (grid square surface) is 25. The set of
parts 1 to 6 should, consistently with balance check, fit. Yet this assumption
finds no scheduling.
If you find one,
contact me!
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Other related
topics
PIC-PDP-ordonnancement
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Author, Chris HOHMANN
is consultant in
industrial performance
and lean manufacturing.
Contact author
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The balance between workload and capacity
assumes the different series can be processed without setup nor dwell time
(parts can be set one touching another).
In reality, some resources need setup operations:
-
drain and clean chemical reactors,
-
emptying and adjusting assembly line,
-
drain and clean paint spray guns and cabins
in paintshops,
-
...
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Scheduling under constraints
A constraint as proposed is frequently met in
paintshops or printing process, where colors must be used from light to dark. |
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Load calculation principles
-
«infinite capacity»: pile up the
workload, regardless to capacity
-
«finite capacity»: arrange batches so
that overlaods will be leveled up
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