What is finite and infinite scheduling? How it is carried out? What is
to be done for each one? What are their significance?
Differences between planning and scheduling, finite and infinite
Finite Scheduling
Scheduling type within capacity planning that takes account of the capacity
loads which already exist. Finite scheduling calculates the start and finish
dates for operations in the order. It is a detailed scheduling strategy with
which you schedule orders and operations, taking into account the existing
resource load. A resource overload cannot occur.
Infinite Scheduling
A detailed scheduling strategy with which you schedule orders and operations,
without taking into account the existing resource load. It is therefore possible
for resource overloads to occur.
R/3 does planning without consideration for capacity situations. So if MRP
says you need 500 parts on 3/1/04, it schedules them all to be built at the same
time, even though you can only do 100 at a time. Assume you have a fixed lot
size of 100, you'll get 5 planned orders for 100 to start on the same day. This
is "Infinite Planning". APO would recognize that constraint, and instead
schedule out the 5 orders over time. The important part of that is that it also
will schedule out the deliveries of the components for 5 different days. This is
"Finite Planning".
Now, assume old fashion MRP. It schedules all 5 orders for the same day, and
the buyers go out an get all of the components for the same day. Then the
planner realizes he can't do all 5, and manually changes the schedule, and
manually spreads out the 5 orders. The buyers will recieve rescheduling
notifications, but not until the scheduler does the manual rescheduling.
You could call this "Infinite Scheduling", but that only means the same thing as
Infinite Planning.
But, SAP has "Capacity Leveling". What that means is you run another program
after MRP (CM27 and CM28), which can be run in batch mode overnight. (There is a
ton of configuration and thinking that will be required to do this!). The
capacity leveling program will recognize the constrant at the work center level,
and fill up the first day, then re-schedule the next
order to the next available capacity, then the next order searches for available
capacity, and so on. This is called "Finite Scheduling". The problem with this
is the opposite of Infinite Planning, which is it doesn't take Material
availablity into consideration! The system will re-schedule a production order
without thinking about whether the materials will be available
or not.
Finite Planning does Finite Scheduling at the same time. If there is no
capacity available on the desired date, the system looks for when capacity IS
available. Then it stops to see if Materials will also be available (usually
based on the lead-time for those components). If there is a material problem,
then the system figures out when the materials WILL be available, and then
checks to see if capacity is available on THAT day, and if so, it blocks off
capacity, and allocates the materials for that day.
