Material Requirements Planning

Material
Requirements
Planning
Chapter 7
Vollmann, Berry, Whybark,
Jacobs
What is MRP (Material
Requirements Planning)

Is a basic tool for performing the detailed
material planning function in the
manufacture of component parts and their
assembly into finished items.
Objective of MRP

To provide the right parts at the right time
to meet the schedules for completed
products.
MRP and MPC
Requires MPS
 Requires Bill of Materials
 Requires Inventory Status data
 Routing file
 Figure 7.1scan

The Basic MRP Record (7.2)scan
(per ciascun oggetto, sia esso materia prima, componente o prodotto finito) pp. 225-227




Anticipated usage of demand for each period
(GROSS REQUIREMENTS richiesta complessiva)
Existing replenishment orders ordini di rifornimento at the
beginning of period (SCHEDULED RECEIPTS)
The current and projected inventory status at the
end of period (PROJECTED AVAILABLE
BALANCE)
Planned dallo scheduler, si aggiungono ai receipts replenishment
orders for the beginning of each period
(PLANNED ORDER RELEASES)
Product Structure Diagram (7.3, 7.4)

It is a technique used to describe the
relationship between the components of a
product and the way these components
and parts are put together in order to
make a complete unit.

Pegging record: Tutti I componenti a tutti I livelli dell BOM possono essere marcati,
oltre che con il proprio part number, anche con quello del componente di livello
superiore a cui appartengono. I prodotti finali anche con il numero d’ordine del
cliente.
Gross to Net Explosion esplosione dal
complessivo all’ordito netto, cioè tenendo conto del disponibile, ovvero
Inventory+Scheduled
Explosion is the process of translating
product requirements into component part
requirements taking existing inventories
and scheduled receipts into account.
 As the explosion takes place only the
components, net of any inventory+Scheduled are
considered. This way only the necessary
requirements are linked thru the system.
 7.5scan

Lead Time Offsetting fig. 7.6/7/8/9 scan
Gross to net explosion tells us how many
of each component are needed for a
finished product.
 The WHEN they are needed is the Lead
Time Offset

Planning Horizon fig. 7.8/9

It should be estimated by calculating the
cumulative lead time for the products
made in the system.
Allocation
and Availability Checking (fig. 7.8; pp. 241-242; picking tickets)
Prior to order launching, an availability
check should be done for the necessary
components.
 If not all available a partial order could be
evaluated in conjunction with marketing.
 After this a picking ticket should be issued
so that items are removed from their
physical location.

Actions of the MRP Planner

Release orders to shop or vendors. Closing that orders occurs
when scheduled receipt are received into stockrooms. Then a transaction
must be processed to increase the on-hand inventory and eliminate the
scheduled receipt.






Reschedule due dates pp. 242-243
Analyze and update system planning factors for
the part numbers under her control
Reconcile errors and inconsistencies
Find key problem areas
Use the system to solve critical material
shortages
Indicate where enhancements would make job
easier.
System Dynamics
It is essential that the MRP system mirrors
actual shop conditions, that is the
information system should have to cope
with scrap, incorrect counts, changes in
customer needs, incorrect BOM,
engineering design changes, etc.
 Figures 7.10, 11 and 12

pp. 244-247 cioè, se un ordine viene cancellato
bisogna propagere la cancellazione a tutti I livelli inferiori della BOM altrimenti viene inutilmente impegnata la
capacità produttiva!
Complex transaction processing
The situations that are faced by the MRP
planner tend to be more complex than
described in the book.
 An example is Fig. 7.13

pp. 247-259
Poi ripresentare da V.Nicolò:
MRP pp. 85=>96
La pianificazione della capacità pp. 97=>100
PAC - Production Activity Control pp. 102-103
Articolazione della pianificazione della produzione
La misura delle prestazioni
Il modello di riferimento dell’attività produttiva
Tipi di processi operativi
Supply Chain