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Transcript of L10_MPS
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MANUFACTURING PLANNING
AND CONTROL SYSTEMS
[WEEK 10]
IML425E 2015-2016 Fall
Assistant Professor Dr. Erkan Gunpinar
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Motivation Three major determinants of the market share and
profitability of any organization are:
1. Cost of manufacturing products
2. Quality
3. Lead time
Achieve goals of:
1. Minimum cost
2. High quality3. Minimum lead time
Manufacturing Planning and Control Systems
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Manufacturing Planning and Control Systems
MPCS
Objective: Desired products are manufactured:- at the right time,
- in the right quantities,
- meeting quality specifications
- and at minimum cost.
Benefits:
- Reduced labor/overtime costs
- Shorter manufacturing lead times
- Reduced inventories
- Etc.
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MPCS Driving force behind any manufacturing activity is the
demand for the products.
Determining end item demand Translating end itemdemand into feasible production
plan
What are processes?
- Define how we do things!
(Step 1 Step 2 Step 3 etc)
What is the role of MPCS?
- Plans the resources that processes use (i.e. people,equipment, material).
- Plans for what processes will be used in the future.
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MPCS
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Resource
Planning
Sales and operations
planning
Demand
management
Master production
scheduling
Detailed capacity
planning
Detailed material
planning
Shop-floor
systems
Supplier
systems
EnterpriseRe
sourcePlanning(ERP)System
Front End
Engine
Back end
MaterialRequirements
Plans (MRP)
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Major elements of MPCS
Demand management
Aggregate production planning
Master production schedule
Rough-cut capacity planning Material requirements planning
Capacity planning
Order release
Shop-floor scheduling and control
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Basic framework for MPCS
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Demand management
Prime mover of any production activity.
Encompasses activities such as:
- Demand forecasting- Order transactions entry
- Customer contact-related activities
- Etc.
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Demand forecasting Estimating future demand
1. Qualitative approach relies on the opinions of experts topredict certain events of interest.
- Surveys, questionnaires.
- Based on experience and intuition.
- Good for long range planning2. Explanatory approach is based on causal relationships.
- Econometric models and system dynamics models.
(growth in economy increases employment increases
buying power of people increases the demand for variousproducts)
3. Descriptive approach is based on statistical models
- Extension of the past performance into the near future.
(Moving average and exponential smoothingapproaches)
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Moving average approach
An average of number of past observations are used to
compute the next day forecast.
+
(=+
)
where +=next forecast for future periods
=demand observations through period
( 1,2, ,)
=average of the most recent observations
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Example
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Exponential smoothing approach
Weight is attached to the moving average approach.
Weight decreases with the age of data.
+ (1)
where += forecast for future periods
=actual demand for period
=smoothed statistic for period
=averaging the demand of the first ( 1)
periods
=smoothing constant
(lie between 0.1 and 0.3)
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Example
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Aggregate production planning
Aggregate the information being processed.- a large variety of products
- time varying demand
- fixed available sources
- a planning horizon
Planning horizon is the time span for which plans are made.
(varies from 6 to 18 months)
Product demand is expressed in production hours or plant
hours.
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Cont.
Production planning is concerned with determining
optimal production, inventory, work force levels to meetdemand fluctuations.
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Cont.
Production Strategy: The goal of this strategy is tocontinuously produce an amount equal to the average
demand.
(accumulating inventories)
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fulfill
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Illustration17
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Master production schedule
It is usually linked to manufacturing where the plan indicates
when and how much of each product will be demanded.
Output of an aggregate production plan does not indicate
individual products.
MPS: Disaggregation into individual products
Output: Master Production Schedule (MPS)
MPS executable?
- No, further analysis is needed for the material and capacity
requirements.
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MPS - Illustration
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Rough-cut capacity planning Objective: ensure the feasibility of master production
schedule.Average amount of work for each product family can be
computed using item`s bill of materials.
Resource profile = amount of work by resource
(Available Resources >= Resource Requirements) If available resources are less than required overtime,
subcontracting, hiring.
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Illustration
Early involve in potential capacity issues and try to find
any solutions to fix them before they happen!
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Material Requirements Planning (MRP)
Information system consisting of logical procedures formanaging inventories of component assemblies, sub-assemblies, parts and raw materials in a manufacturingenvironment.
Key concepts:
1. Product structure and Bill of Materials (BOM)
2. Independent versus dependent demand
3. Parts explosion
4. Gross requirements
5. Common-use items
6. Etc.
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Product structure and BOMA product may be made from one or more assemblies, sub-
assemblies and components.
BOM is an engineering document that specifies the
components and sub-assemblies required to make a product.
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parent
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Gunpinar et al. 2008
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Gunpinar et al. 2008
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Gunpinar et al. 2008
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MRP key concepts
Independent demand: demand for the end items originatesfrom customer orders and forecasts.
Dependent demand: demand by a parent item for itscomponents.
Parts explosion: requirements for the subassemblies,components and raw materials for a given number of end-items.
(explosion of parents into their components)
Gross requirements: determine the amounts of eachcomponent item required to obtain one parent item.
(BOM possesses this information)
(Demand of Comp.x= Demand of product * No. of comp.x)
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Example
If the demand for end product E1 in period 7 is 50 units for
the previous BOM in page 20, determine the dependent
demand (gross requirements) for subassemblies and
components.
- Demand of S1 = 50 x demand of E1 = 50 units
- Demand of S2 = 50 x demand of E1 = 100 units
- Demand of C1 = 50 x demand of S1 = 50 units
- Demand of C2 = 50 x demand of S1 = 100 units
- Demand of C3 = 50 x demand of S2 = 200 units
- Demand of C4 = 50 x demand of S2 = 300 units
- Demand of C5 = 50 x demand of S2 = 100 units
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MRP key concepts
Common-use items: many raw materials and componentsmay be used in several subassemblies of an end item and
several end items.
(components C2 and C4 are common to both E1 and E2)
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Cont.
On-hand inventory: initial inventory for some of thecomponent items are available from previous productionruns.
Scheduled receipts: the orders placed now are delivered into
some future periods. Net requirements = gross requirements on-hand
requirements
Planned order releases: process of releasing componentitems for production or purchase.
Lead time: time it takes to produce or purchase a part.
Lead time offsetting: manufacture or purchase of componentsmust be offset by at least their lead times to ensureavailability of these items for assembly into their parent items.
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Example
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Offset three weeks
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Capacity planning
Planned order releases are tentative because of the
capacity limitation of work centers
Check feasibility of production plans develop an
executable manufacturing plan
A number of decisions should be made:
1. Exploring overtime/subcontracting options
2. Developing alternative process plans for effective
resource utilization
3. Inventory options
4. Determining sources such as machine tools
5. Etc.
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Order release
Directive to work Orders are released to the shop floor once production plans
are executable.
Documents accompanying the order:
1. material inventories allocated to the order2. routing sheets (operation sequences, machines)
3. appropriate shop records (job cards, parts lists)
Important activities:
1. scheduling of job orders on the work centers2. allocation of jigs and fixtures
3. loading work centers considering optimal loading conditions
4. coordination of material handling, storage
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Example of a routing sheet
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Shop-floor control
Schedule adherence is of primary concern for the work
centers and the vendors.
Random events such as failure of machine tools or other
equipment affect schedule adherence product delivery
To minimize the impact of random events, efficient shop-
floordata collection and information system is required.
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Data collection
Handwritten reports
Manual data entry terminals
Bar code readers and sensors
(automatically update an item`s progress through the shop floor)
Voice data entry system
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Work order status
Work order status is updated several times per week and
is used:
- To monitorthe progress of manufacturing activities
- To determine priorities for scheduling jobs in the shop
- To control work in progress
- To provide output data for capacity control purposes
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Bar code systems for shop-floor control
Used for:
- Item identification for inventory control
- Work-in-process tracking
- Distribution tracking- Monitoring the status of items in manufacturing
Major elements are symbology, printer, medium, scanner,
decoder.
Bar code symbology is the process of converting a
computer message into bar code symbol.
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Steps for barcode symbology1. Establish the type of data to be represented and the
number of characters in the message.
2. Translate the human-readable information into a binarysequence.
(industrial 2 of 5bar code family)
3. Create a bar space pattern representing the binary word
(black bars and white spaces)
(narrow bar
0, wide bar
1 for industrial 2 of 5 code)(http://www.barcodeman.com/info/c2of5.php)
4. Format the bar code characters into a bar code symbol
(add start and stop margins)
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2 of 5 Code Character Encodation
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Bar code elements
Medium: optical storage device on which bar code
symbols are printed.
(adhesive labels, cards)
Printing mechanism deposits ink on the medium.
(ink-jet, laser)
Scanner: binary data encoded in a bar code symbol is
extracted by an optical system.
(emitter, detector, optical lens) Bar code reader: decoder acts as data interpreter
provided by the scanner.
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Bar code readers
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Framework for shop-floor control using bar codes
When an order arrives at a work center, operator scans the
bar code with the help of a bar code reader attached to amicro computer.
Microcomputers are linked to a main computerwhere
operator retrieves updated process planning and scheduling
information.
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Operations scheduling
Two major difficult activities are performed:1. Work orders are assigned to work centers
(machine loading).
2. Sequence of each work is determined
(job sequencing).
One of the most important objective for operations scheduling
is to meet due dates.
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Scheduling and Loading
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Job sequencing and priority rules
Total number of jobs may exceed the number of work
centers.
Priority rules:
- First-come, first-serve (FCFS)
- Shortest processing time (SPT)
- Earliest due date (EDD)
- Least slack (LS)- Etc.