With all the talk of advanced manufacturing techniques,
there is a risk that we forget about the basics, which is
the foundation upon which manufacturing excellence
is built. The purpose of this talk is to discuss a perspective
about one of those basic practices that helps a manufacturing
company convert plans to actions—the Master
Production Schedule (MPS).
EVOLUTION OF THE MPS
Our knowledge of how to properly manage the MPS
function has gone through a significant evolution of
change and improvement. In the beginning (1960s),
when MRP (Material Requirements Planning) was a new
subject as part of the development of today's demand-driven
global economy, we did not give much thought
to the proper use of a "master schedule" to truly schedule,
and more importantly, reschedule. The market "forecast"
was simply exploded through bills of material,
creating factory and supplier
schedules at whatever levels the market demanded, regardless of the company's
We then began to recognize that in order to manage
within the short-term constraints of our factories and
our suppliers (capacity), we could not simply assume
"infinite capability." Additionally, we began to recognize
the need to reschedule as things indeed changed in
the marketplace, in the factory, and with suppliers. To not change
the MPS would invalidate all priorities, degrading the integrity of the entire system.
All this gave rise to a defined and disciplined Master Production
Scheduling process, whose overall objective
was to bring balance to supply and demand. The MPS
became the center of the planning system—creating
rough-cut balance between our finite capability and the
needs of the marketplace. It then drove the detail of
material and capacity planning. We then began extending
the MPS horizon beyond the Critical Time Fence
so that we could see detailed
resource needs in a
timeframe that would enable appropriate decisions
about acquiring capacities to
satisfy customer's needs.
The computer and its ability to store and display large
amounts of data made it possible to "manage" this process far into
the future, and we did just that—often to a full year. Software
suppliers began to develop ways to
automate and make this extended practice more efficient.
This got us into such detail that we sometimes got lost in
the woods, not seeing the big picture. It also
became an administrative burden
to maintain it.