Chapter 10 Manufacturing Planning and Control Systems

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Chapter 10Manufacturing Planning and Control
Systems
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Agenda

• A Basic Framework for A Manufacturing Planning
  and Control System
• Demand Management
• Aggregate Production Planning
• Master Production Schedule
• Rough-cut Capacity Planning
• Material Requirements Planning
• MRP Lot-sizing Problem
• Capacity Planning
• Order Release
• Shop-floor Control

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A Basic Framework for a MPCS

• Objective ensure that the desired products are
  manufactured at the in the ,
  meeting specifications, and at .
• Benefits
• Reduced inventories
• Reduced capacity
• Reduced labor and overtime costs
• Shorter manufacturing lead times
• Faster responsiveness to internal and external
  changes such as machine and other equipment
  failures, product mix and demand changes, etc.

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Demand Management

• Activities demand forecasting, order
  transactions entry, customer contact-related
  activities, physical distribution management
• Forecasting approaches
• The qualitative approach rely on opinions of
  experts
• The explanatory approach base on causal
  relationship
• The descriptive approach statistics
• Moving average xt a0 ?t
• The forecast for any future period based on N
  recent observations
• Exponential smoothing the forecast for ? future
  periods for the constant model

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Examples 1
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Example 2
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Aggregate Production Planning

• Production planning is concerned primarily with
  determining , , and to meet demand
  fluctuations
• APP obtain solutions by aggregating information
  (production hours) for a large variety of
  products, time-varying demand, a long planning
  horizon, fixed available resources
• Strategies to manage to absorb the demand
  fluctuations
• Maintain uniform and accumulate
• Maintain uniform by vary by permitting
  planned overtime, subcontracting, etc.
• Change production rate by changing the size of
  the workforce
• Explore the possibility of planned backlogs if
  customers are willing to accept delays in filling
  their orders
• ? combination of strategies ?develop an optimal
  APP

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A Mathematical Programming Model

• Where dt aggregate demand in period t Xt
  production units scheduled in period t cx
  variable cost of production excluding labor per
  hour Ot overtime scheduled in period tco
  over time labor cost per hour Ut undertime
  allowed in period t cu opportunity cost of not
  using the equipment Wt regular time workforce
  in period tcw cost of regular time labor per
  hour Ht new labor force added in hours in
  period tch cost of hiring regular time labor
  per hour Ft layoffs in hours in period tcf
  cost of layoffs per hour ci cost of unit
  inventory holding per hour cs cost of a
  shortage per hour K labor hours required to
  produce a unit T number of periods in the
  planning horizon It inventory in stock at the
  end of period t I-t shortages at the end of
  period t

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Master Production Schedule

• Master Production Schedule output of a
  process of the aggregated production plan for
  
• Executable manufacturing plan master production
  schedule, capacity planning, material
  requirements planning

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Rough-cut Capacity Planning

• Objective to ensure that the master production
  schedule is feasible
• Calculate the needed on work centers
  per unit for each product family based on BOMs
  and routings
• The resource profile (the amount of work by
  resource/ unit of output) is developed
• Compare the available resources with the resource
  requirements profile obtained for all the work
  centers considering all product families
• Example Resource profile for two product
  families
• Work center Family I Family II Total
  required
• (h/200units) (h/200units) resources
• 1100 14 7 21
• 2100 7 20 27

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Material Requirements Planning

• An information system consisting of logical
  procedures for managing of components,
  subassemblies, parts, and raw materials
• Objective How many? When? (determine net
  requirement for periods)

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Example 3
The manufacturing/assembly lead times for E1, S2,
and C4, ordering lead time for M4, information on
on-hand inventory, and scheduled receipts are
given in able 10.9 ( the solution table). Carry
out the material requirements planning procedure
for raw material M4 required to manufacture
component C4
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MRP Lot-sizing Problem

• Where
• T number of periods in the planning horizon
• aj 1 if xjgt0 0, otherwise
• dj demand in period j
• xj production quantity in period j (decision
  variable)
• Ij inventory level in period j (decision
  variable)
• hj holding cost/unit in period j
• cj variable production cost/unit in period j
• Sj setup cost in period j

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Solution Algorithm (W-W Algorithm)

• The optimal solution for periods 1,2..,k given Ik
  0

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Example 4

• Consider a 4-period problem having no initial
  inventory. The data are given in the following
  Table

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Example 4
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Capacity Planning

• Capacity planning is concerned with such as
  labor, equipment to ensure the feasibility of
  production plans

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Order Release

• When the production plans obtained from MRP
  system are executable, the orders are released to
  the shop floor
• Documents
• Order
• Material inventories allocated to the order
• Routing sheets operation sequences, machines,
  etc.
• Appropriate shop records (job cards, move cards,
  parts lists) for assembly jobs
• The order release triggers the shop-floor control
  activities
• Scheduling of job orders on the work centers
• Sequencing of jobs on a work center
• Allocation of jigs and fixtures
• Loading of work centers considering optimal
  loading conditions
• Coordination of material handling, storage,
  warehousing, and machine tools

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Shop-Floor Control

• Functions of a shop-floor control system
  job orders on the work centers, to on a work
  center, to provide accurate and timely
  information
• Order status information
• batch sizes
• job completions
• remaining jobs and operations
• time for all remaining jobs and operations
• Use for
• To monitor the progress of manufacturing
  activities
• To determine priorities for scheduling jobs in
  the shop in response to changes in job order
  status
• To maintain and control WIP
• To provide output data for capacity control
  purpose

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Shop-Floor Control

• Two main functions of a shop-floor control system
• Machine loading allocation jobs to work centers
• Job sequencing sequence jobs at each work center
• Scheduling objectives
• Meeting due dates
• Minimizing manufacturing throughput time
• Minimizing WIP
• Maximizing work center utilization

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Shop-Floor Control

• Sequencing and Priority Rules
• First-come, first-served (FCFS)
• Shortest processing time (SPT)
• Earliest due date (EDD)
• Least slack (LS) slack time remaining until
  due date processing time remaining
• Least slack per operation (LSPO)
• Critical ratio (CR) CR time remaining until
  due date/lead time remaining
• Comparison of various scheduling rules using
  common performance

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Example 5
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Example 5
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Shop-Floor Control

• Bar Code Systems for Shop-Floor Control
• Bar coding technology is being used in industry
  for and .
• Types of data in bar codes
• Item identification
• WIP tracking
• Distribution tracking
• Other manufacturing control functions process
  steps, inspection results, equipment settings,
  failure mode
• Elements of a bar code system symbology, media,
  printer, operator, scanner, decoder
• Symbology process computer information ? bar
  code symbol
• Step 1 establish to be represented and the
  in the message
• Step 2 translate the human-readable information
  into a
• Step 3 create a representing for binary word
• Step 4 format the individual bar code characters
  into a that represents the complete message

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Symbol encode-decode sequence
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A framework for shop-floor control using bar codes