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)

150

150

50

150

Conflitto tra B e Cin sett 8

previsto

effettivo

To production

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 andTime 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