ESI 6529 DIGITAL SIMULATION TECHNIQUES

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ESI 6529 DIGITAL SIMULATION TECHNIQUES

• Lecture 11

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Evaluation of Production Control Policies

• Consider a manufacturing system which consists of
  multiple machines and multiple process flows.
• When to release new materials into the system and
  what to release?
• When to load a machine and which part to load?
• How to evaluate the system performance?

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A Three-Machine Reentrant flow shop
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Releasing Policies

• Constant Input
• Poisson Input
• CONWIP (or Closed-Loop) Input
• Workload Regulating Input

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CONWIP(N)

• The number of parts in the system is held
  constant, where N is the total work-in-process.

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Workload Regulating

• Release a part into the system whenever the total
  amount of remaining work in the system for some
  bottleneck machine falls below a prescribed
  level.
• WR(t), where t is the total workload.

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Dispatching Policies

• First-In-First-Out (FIFO)
• Last-In-First-Out (LIFO)
• Shortest-Remaining-Processing-Time (SRPT)
• Longest-Remaining-Processing-Time (LRPT)

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Control Policies

• POISSON-FIFO
• CONWIP(N)-FIFO
• WR(t)-FIFO
• CONST-SRPT
• CONWIP(N)-SRPT
• WR(t)-LRPT

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Performance Measurement

• Work-In-Process (WIP) Inventory
• Flowtime (or Cycle Time)
• Lateness
• Expected Total Cost

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BEGIN PROJECT, SimpleSys, Bai ATTRIBUTES
OpTime, ArrTime QUEUES 6 STATIONS STAT1
STAT2 STAT3 ExitSystem RESOURCES
Machine(3) SEQUENCES 1, STAT1, 2 STAT2, 2
STAT3, 2 STAT1, 2 STAT2, 2 STAT3, 2
ExitSystem TALLIES FlowTime REPLICATE, 1,
0, 300 END
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BEGIN CREATE Expo(1) MARK(ArrTime) ASSIGN
NS1 GO ROUTE 0.0, SEQ STATION,
STAT1-STAT3 QUEUE, IS SIEZE
Machine(M) DELAY OpTime RELEASE Machine(M)
NEXT(GO) STATION, ExitSystem TALLY
FlowTime, INT(ArrTime) DISPOSE END
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POISSON-FIFO
b2
M1
b1
b3
M2
M3
d
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CONWIP-LRPT
b1
b3
b2
M1
M2
M3
d
b5
b6
b4
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BEGIN PROJECT, CONWIP, Bai ATTRIBUTES OpTime,
ArrTime VARIABLES PartSys N, 10 QUEUES 6
EnterQ FinalQ CustQ STATIONS STAT1 STAT2
STAT3 ExitSystem RESOURCES Machine(3) SEQUENC
ES 1, STAT1, 2 STAT2, 2 STAT3, 2 STAT1,
2 STAT2, 2 STAT3, 2 ExitSystem TALLIES
FlowTime REPLICATE, 1, 0, 300 END
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BEGIN CREATE 1 NEXT(ORDERS) CREATE ASS
IGN NS1 STORE QUEUE, EnterQ SCAN PartSys
.LT. N ASSIGN PartSysPartSys1
MARK(ArrTime) BRANCH, 2 ALWAYS,
STORE ALWAYS, GO GO ROUTE 0.0,
SEQ STATION, STAT1-STAT3 QUEUE, IS SIEZE,
6-IS Machine(M) DELAY OpTime RELEASE
Machine(M) NEXT(GO) STATION,
ExitSystem INV QUEUE, FinalQ
Detach ORDERS QUEUE, CustQ Detach MATCH
INV, OUT ORDERS OUT TALLY FlowTime,
INT(ArrTime) ASSIGN PartSysPartSys-1
DISPOSE END
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KANBAN Control Policy

• Each part is associated with a Kanban
  (information card)
• The production process is divided into different
  stages
• Each stage processes a part only when there is a
  demand from the downstream stage
• The last stage relinquishes a finished product
  when a customer demand arrives this frees a
  Kanban which becomes a demand for the previous
  stage

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Single-Card KANBAN System
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Single-Card KANBAN System with Minimal Blocking
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Two-Card KANBAN System
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A Three-Machine Reentrant flow shop
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