If the capacity Planning and the Master
Schedule expressed the reality, then prioritizing the production orders would
be meanless, since everything would be done in time.
In real life thing things are different. There
will be many cases where several production orders must be executed in a period
that the capacity is not enough. MRP will not catch this problem, as it always
assumes infinite capacity.
I’ve heard of many approaches basically applied
on large ERPs such as SAP or SAGE but in my case, there was no way of
prioritizing.
After giving the issue some thought, I decided
that all that was really needed was a priority FLAG. The user could just see
the flag and manually give priority to some orders against some others. The
idea came back from my days in the army. We had four priority levels on every
military document that signified the level of urgency. Check on Wikipedia to
see what I mean (http://en.wikipedia.org/wiki/Message_precedence).
In my case, three priority levels were only
necessary and this is what I’ve done:
·
Immediate
(I) : High-Priority
When Stock-Reserved <0
·
Urgent
(U):
Medium-Priority
If not “I” and Stock-Safety
Stock-Reserved
<= 0
·
Routine
(R): Low Priority
When it is not either “I” nor “U”
The “I”
flag signifies that a SKU has a stock level which is lower than the pending
orders, that will due in the current time bucket. If you don’t react
immediately then you will just increase your backlog and receive complaints.
The “U”
flag signifies that your current stock is enough for fulfilling the pending
orders but after fulfilling them, it will be dropped below the safety stock
levels. This is a sign of alertness. Safety stock is supposed to be carried
from period to period in order to absorb any failure of the system, to fulfill the
demand. It is a wise idea to release a production order while the SKU is
still on a “U” state.
Finally, the “R” flag signifies no special alertness. Your pending orders can be fulfilled
by your stock and even after fulfilling them your safety stock will be enough
to absorb any other shocks. There is no hurry on producing this SKU but it
should be produced as the MRP is committed to the MPS.
What you see above is an IF…Clauses statement,
that can be very easily calculated even “on the fly” from an SQL query. A sorted
report can be generated and the user can easily choose to release first, the
production orders with the highest priority level.
