Let's turn our attention to the connected flow manufacturing
environment. This environment is characterized by the operation
time (set-up, run, tear-down) consuming 80% or more of the total
throughput time. Work cells, short material transportation
distances, small queues, point-of-use material storage, and
Kanbans are commonly found in this environment, and often times,
work orders are not issued to production.
The choice of capacity planning techniques in
this environment depends primarily upon two factors—product mix
and variation in volume. If the product mix scheduled through a
resource does not vary much, or if all products consume
approximately the same amount of that resource per unit, capacity
planning can be done by merely increasing or decreasing future
available capacity in proportion to the total product volume
Figure 5 is a typical short term capacity plan
for a connected flow environment for similar products. Note that
capacity is planned in product units rather than hours, since each
product consumes approximately the same amount of resources, and
the schedule is arranged to level the load on the plant in terms
of product output. Mid to long term plans would show capacity
requirements in terms of product output that would be similar to—if
not identical to—the Master Schedule.
It is this situation that has led to the notion
that JIT plants don't need to do any capacity planning, they just
use the Master Schedule. It is merely semantics. They still do
plan capacity, just in different terms. If the Master Schedule
indicates an anticipated increase in output, then an increase in
capacity must be arranged in advance. That is the essence of
If the capacity requirements vary noticeably with changes in
product mix, or if volume changes are irregular, then a more
detailed capacity planning and scheduling technique is necessary.
In this case, the CRP technique as described above for the
disconnected flow environment may be used, but the process itself
might be somewhat simplified by using abbreviated routings (often
one step), fewer work centers (cells), and no released shop orders
(scheduled receipts, in MRP terms). In fact, some flow
environments use only RCCP as the capacity planning technique if
the limitations of that process noted above are not an issue.
except that the resources consumed per unit
vary by product. In this situation, the capacity planning process
is essentially the same as CRP. The scheduled quantity is
multiplied by the resource required per unit and a total capacity
required is aggregated from all of the product scheduled for the
period (in this case, daily.) Note that the load on the plant has
been leveled in hours now rather than in product units.
In the connected flow environment, input is
inseparably linked to output. Thus, the need for classic
Input/Output Control is eliminated. However, output against plan
is monitored very closely in such environments, so I suppose one
could say that Output Control is being used. Again, it is
Regardless of the environment—MRP II or JIT,
disconnected flow or connected flow, fabrication or process—every
manufacturing company needs to plan capacities. The further
forward that a company can look to reveal potential imbalances
available capacity and required capacity, llic
better they will \><-. able to correct the situation
and avoid the rush arid chaos -.<, prevalent in many
companies. The process for doing this is fundamentally the same in
1. Run the Master Schedule up against a set of data that will
predict the capacity required to do it by time period.
1. Compare the results of step 1 to the capacity that is
expected to be available in each period.
3. Initiate action to correct imbalances identified in step
What differs is the level of detail that is
employed to do the job. That varies with the environment.
Examine your situation carefully. Don't reject a technique or
process because someone said it didn't apply, you don't
understand it, or you tried it once (probably incorrectly) and
it didn't work. Employing the proper techniques properly (the
redundancy is intentional) is the key to winning the global
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