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Date Submitted: 12/06/2012 07:20 PM
Chapter 11
MRP and JIT
(Material Resources Planning and Just In Time)
11.1. MRP
Even if MRP can be applied among several production environments, it has been
chosen here as a preferential tool for the management of diversified production called job
shop production.
This method is based on master production planning (forecasts and confirmed orders)
which is transposed in the operational objectives of this plan which are the Purchase orders
for the components or raw materials and the work orders for the resources (men and
machines).
To compute this method, a lot of basic data is required:
- the detailed bill of material of every product;
- the furnisher’s delay and production lead time for every product;
- the routes (resource requirements).
Time has been spent before reaching the sufficient computing capacities required to
optimise a system with such a philosophy.
The result is a noticeable improvement in productivity as the right component arrives
at the right time on the right machine operated by the right human resources. Workshop
managers do not have anymore to run and look after missing parts and purchasers don not
have to follow and pay for urgent orders. Everybody can do his or her own job without stress
and with real added value.
MRP is a closed loop system. The scheduling (list of jobs and operations achieved
within a time limit) is effectively applied after a test of availability.
MRP I = first generation = availability of components
MRP II = 2nd generation = availability of components and resources.
The input of the system is the master production planning which is based on the
forecasts which are transformed in successive steps of production which is called the master
production schedule.
This transformation is different either if the system only works on confirmed orders or
for stock (order anticipation) or a mixed system.
In the first case, starting from confirmed orders, usually a few months’ horizon is
taken into...