Material Requirements Planning
As we develop from discrete
to repetitive, materials planning goes from job order based to
demand-pull, or rate based.MRP is an order launching system that
works well in a discrete environment with very vertical bills of
material with defined lead times.
Repetitive manufacturing does not work in discrete lots which
makes MRP more difficult to work with it. But, by using phantom
bills, we can explode our requirements through the product and use
MRP to help us plan our resources.
Capacity Requirements Planning
Most discrete manufacturing processes or job shops are very
conscious of the need to match capacities to capabilities and
create workable plans from this information. Because of variations
in routings, this is an area which requires both a combination of
infinite capacity planning to determine loads, and finite capacity
planning to create the actual plan.
Discrete manufacturing can take advantage of alternate routings
to help deal with capacity constraints and possible bottlenecks.
Capacity can be increased with overtime and more shifts.
In repetitive manufacturing, the routings cannot be changed, only
taken off-line. Rate and mix of demand have a major impact on
capacities with major changes not easily accomplished due to
equipment dedicated to pre-set levels of production.
Production Activity Control
There are two major systems for controlling the shop floor: job
orders and signals. How we manufacture is going to determine which
system will work best in our environment.
Where volume is small and variety high, such as in a job shop, a
job order fits best for controlling production. Priorities become a
major factor, since the various work orders compete for work center
capacity. Using work orders can be thought of as a way of reserving
the capacity needed at the work centers. In addition, we report back
to the system the completion of operations to allow updates and
Due to the flow nature of repetitive manufacturing, we work better
by responding to a signal of need from work center to work center.
We need not reserve capacity, nor need we report the completion of
individual operations. Instead, we report the completion of an item
which can then backflush through the process to charge material and
In a mixed mode environment, both types of control will be found.
The ability to produce to work orders and report against them, along
with the ability to produce to signals and backflush after the fact,
becomes a necessity. A KANBAN signal system for manufacturing can be
used while still producing to work orders in anticipation of
customer orders for final assembly.
As we evolve into focused factories and our processes become more
sophisticated, planning systems have to be compatible with methods
Manufacturing planning software needs to be acquired with the
ability to accomplish all that we demand from it. The software firm
has to be able to advise and train us as to how we can best
implement and use it, and then be available for continued support.
For mixed mode manufacturing to be successful, there has to be a
change from centralized to a more decentralized planning
organization. This is where people empowerment becomes necessary
since any attempt to control every aspect of the process over a mix
of processes becomes an impossible task.
One method is to empower the workers to build on their knowledge
of the product and what it takes to build it. This is done through
education and trust that workers have intelligence and know their
job better than anyone else.
This is a revolutionary change in thinking that is occurring out
of absolute necessity. When you embrace mixed mode, the environment
is so dynamic that decentralization may be the only way to
accomplish your goals. The days of the central planning organization
are giving way to a centralized management that creates the
business plan or strategy and then empowers the executors of the
plan to make it happen.
Getting There and Staying There
Most companies will adopt whatever manufacturing strategies are
necessary to meet their goals and needs. Whether mixed mode is in a
company's future depends on its market niche, market share, or what
is needed internally to manufacture the product. It can be an
evolutionary process of change, or be fully embraced and become a
revolution. In the long run, the benefits of mixed mode
manufacturing are substantial.
The first step is to recognize what you have, then what you need.
Make any necessary changes and use them for your continuing success.
The concepts discussed can adjust to increases or decreases in
either variety or volume over the life of a product. This
recognition is the key to success.
For balance of this article, click on the below link:
Lean Manufacturing Articles and go to Series 02