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) 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 be compatible with the 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.

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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

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Options or modules from which a variety of end products could be assembled.

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Numbers of units of an “average” final product

Conversion of MPS is

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Controlled by a separate Final Assembly Schedule (FAS) which is defined at the very last moment.

For the Make-to-Stock firm

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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

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Rolling through time

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Order promising  Available

to promise (ATP)

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).

Indented BOM

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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, 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.  The most widely used is called the super bill.(6.14) 

Final Assembly Schedule (FAS) 

FAS job is to convert MPS records into FAS records as we roll through time. (6.17)

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) 

Examples Ethan Allen 6.21, 6.22  Jet Spray 6.23 

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 

Strike a balance where stability is monitored and managed by:  Use

firm planned order treatment for the MPS quantities  Frozen time periods for the MPS and  Time fencing to establish clear guidelines for the kinds of changes that can be made.  6.24

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 

Managing the MPS 

Start by having a realistic MPS

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Stability and proper buffering are important to remove all the excuses for not attaining the performance for which the proper budget has been provided.

The Overstated MPS The overstated MPS erodes belief in the formal system.  Always force the sum of the MPS to equal the production plan.  Mfg & Mkt should work diligently to respond to product mix changes but within the budget. 

MPS Measures Measure MPS in concrete terms that reflect the firm’s fundamental goals.  Measure customer service (hit promised dates, Quality, etc.).  Compare production vs. plan  Keep records of backorder supply time to improve them. 