Chapter 6 Master Production Scheduling

Chapter 6
Master Production
Scheduling
Vollmann, Berry, Whybark, Jacobs
What is the MPS?
The MPS translates the Sales &
Operations Plan (SOP o PP) into a
plan for producing specific products in
the future.
 The MPS is the translation of the SOP
into producible products that make up
the output.

At the operational level . .
The MPS is developed to generate a
sustainable Materials Requirement
Planning (MRP) system and to
provide the information for
coordination with sales.
 The MPS is a statement of planned
future output.

As a statement of output, the
MPS

Forms the basic communication
between the market and
manufacturing.

Is stated in product specification terms
(part numbers) for which there are Bill
of Materials (BOM).
MPS can be stated in
terms of?

End-item product designations

Options or modules from which a
variety of end products could be
assembled.

Numbers of units of an “average” final
product
Conversion of MPS is

Controlled by a separate Final
Assembly Schedule (FAS) which is
defined at the very last moment.
For the Make-to-Stock firm

The items are produced in batches,
carrying finished goods inventories for
most, if not all, end-items.
For the Make-to-Order firm
In general, it carries no finished goods
inventory and builds each customer
order as needed.
 The MPS unit is defined as the
particular end-item composing a
customer order.
 Production often starts before a
complete product definition or BOM
has been determined.

For the Assembly-to-order
firm

The MPS unit is typified by an almost
limitless number of possible end-item
configurations all made from
combinations of basic components
and subassemblies. Probably will not
start final assembly until order arrives.
Linkages to other firm
activities
It receives information from the SOP
which in turn receives info from Demand
Management (Forecasting) and resource
planning.
 In addition it is linked to ERP (planning)
and rough-cut capacity (make sure we
can make it) planning.
 It generates information for MRP

MPS Techniques

Time phased record (cadenza temporale delle
previsioni per ogni item, con MPS livellato, di inseguimento
o a lotti)

Rolling through time (aggiornamento dell’MPS “lungo”
la cadenza temporale)

Order promising (ordini a consegna differita)

Available to promise (ATP) (quanti ordini differiti
posso accettare
Bill of Materials Structuring
for the MPS

It is an engineering document that
specifies the ingredients (or
subordinate components) required
physically to make each part number
or assembly.
Single-level BOM

Comprises only those subordinate
components that are immediately
required (not the components of the
components). Adatto per il MTS: make to stock,
dove il MPS è specificato in termini di prodotto finale.
Indented BOM

Is a list of components, from the end
item, down to the raw materials (it
does show components of the
components).
Other definitions
BOM files are those computer records
designed to provide desired output
formats.
 BOM Structure relates to the architecture
of the BOM files
 BOM Processor is a computer software
package that organizes and maintains
linkages in the BOM as dictated by the
BOM structure.

More definitions
Product Structure a company should have
one and only one set of BOM records.
 Low-Level Code number should be
designated for each part, component,
subassembly or finished item in the BOM.
These numbers indicate where in the
product structure a particular item is with
respect to the end item.

Modular BOM

When the combinations of end-item product are
many ad esempio in una fabbrica automobilistica che produce grande varietà
di prodotti finali, tenendo conto delle varie combinazioni di opzioni o moduli, it is
better to use the MPS at the option or module
level. The MPS is stated in the terms in which the
product is sold not built. cioè in termini di BOM dei vari moduli della
configurazione, ordinata dal cliente

The most widely used is called the super bill.(6.14)
: la configurazione costituisce un single-level BOM che serve principalmente per la
previsione di vendita (ma anche per montare il prodotto finale); nel super-bill ogni
opzione è pesata con la media della sua presenza nelle configurazioni prodotte (se
si vendono 1000 auto con 2 porte e 500 con 4 porte, la media è 8/3). Il SOP/PP e
l’MPS si fanno allora in termini di super bill. Le medie del super-bill sono valide nel
lungo periodo e vengono assorbite nel breve periodo da Safety Stock dei singoli
moduli. I livelli dei Safety S. sono mantenuti dall’MRP.
Final Assembly Schedule
(FAS) fig. 6.17-6.18-6.19

FAS job is to convert MPS records into FAS
records as we roll through time. (6.17)
La configurazione finale è gestita con il FAS secondo un principio pull: dall’ordine si
risale alla configurazione e si accetta l’ordine (eventualmente differito) se sono (o
saranno) disponibili i componenti; quindi parte l’ordine di eventuale loro finitura e
l’assemblaggio finale. In sostanza i componenti sono prodotti make-to-stock e il
finale assembly-to-order.
Tutto ciò va bene per produzioni ripetitive a numerosità medio-alta o al più media
(ricordare il diagramma). Quando la numerosità è più bassa ci può essere la
variante che componenti non disponibili, necessari ad accettare un ordine,
vengono inseriti, con una variante, nell’MPS di produzione dei componenti.
The Master Production
Scheduler

Its useful to think of the MPS as a set of
firm planned orders. The scheduler
needs to convert planned orders to firm
planned orders and to manage the
“timing” and amounts of the firm planned
orders.
The Job of the Master PS
Primary responsibility for making any
additions or changes to the MPS records.
 Has also has responsibility for
disaggregating the production plan to create
the MPS and that the sum of the detailed
MPS matches the Production Plan (SOP).

The Job of the Master PS
Responsible for launching the FAS.
 Making sure that there is only one unified
database for the MPS
 Measure actual performance against the
MPS and production plan (SOP)

effettivo
50
previsto
To production
Conflitto tra B e C
in sett 8
150
150
150
MPS Stability
A stable MPS translates into stable
component schedules, which means
improved performance in plant operations.
 Too many changes – lower productivity
 Too few changes – lower customer service
levels.

Increasing MPS stability

Stability is monitored and managed by:
Frozen time periods for the MPS and
 Time fencing to establish clear guidelines
for the kinds of changes that can be made.

Frozen Schedule

This means that for the more recent time
buckets it will be very difficult (but still
negotiable) to change the sequence in
which the orders will be processed.
Time Fencing
This is an extension of the freeze concept.
 Many companies set time fences that
specify periods in which various types of
change can be handled.
 In the Demand fence the forecast is
ignored in calculating the available
(difficult to change the MPS).
 The planning fence indicates the time at
which the scheduler should be planning
more MPS quantities. per consentire
“management trade-off to make changes”

Managing the MPS

Start by having a realistic MPS
Stability and proper buffering are
important to remove all the excuses for
not attaining the performance for which
the proper budget has been provided.
 6.24
