Ch 12 Transport

Altiok / Melamed Simulation Modeling and Analysis with ArenaChapter 12

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SIMULATION MODELING AND ANALYSIS SIMULATION MODELING AND ANALYSIS WITH ARENAWITH ARENA

T. Altiok and B. MelamedT. Altiok and B. Melamed

Chapter 12Chapter 12

Modeling Transportation SystemsModeling Transportation Systems


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• Examples of simulation modeling and analysis projects for transportation systems include

• designing new traffic routes and alternate routes to satisfy demand for additional road capacity• eliminating bottlenecks and congestion points in existing routes by appropriate placement of traffic lights and tollbooths• designing traffic patterns on the factory floor, including transporters and conveyors, for efficient movement of raw material and product• designing port facilities, such as berths and piers, and allocating vessels to berths, where such designs include material handling systems (loaders/unloaders, transporters, conveyors and others) for containers and bulk material transport• designing new airports or adding runways to existing ones to satisfy demand for additional flight capacity, where such designs include air traffic patterns and routing, runway scheduling and planning cargo operations

Examples of Transportation Systems


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• The panel supports modules that provide additional mechanisms of time-lapse transfer of Arena entities among Station modules or geographic locations

• Route modules may be used as dispatch points, and Station modules as destination points

• Transporter and Conveyor modules may be used for material transport

• the Enter and Leave modules may be used to transfer entities into and out of physical or logical locations

• the PickStation module allows entities to select a destination Station module using a selection criterion, such as the minimum or maximum of queue size, number of busy resource units, or an arbitrary expression

• alternatively, an entity can be endowed with an itinerary using the Sequence module to specify a sequence of Station modules (referred to in Arena as Step objects)

Advanced Transfer Template Panel


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• A Station module is used to designate a physical location or a logical location in the model

• example: a physical location might be a milling station that physically houses milling machines• example: a logical location might be a dummy station at a model site close to a cluster of related modules

• A Route module is used to route (transfer) entities to Station modules at various locations in the model

• the destination Station module may be specified in an entity attribute as an expression, as a Station module name, or as part of an itinerary defined in a Sequence module• Route modules are not graphically connected to destination Station modules

Station and Route Modules


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• The Advanced Transfer template panel also provides specialized transportation facilities for material handling in manufacturing-related systems

• a Transporter module is used to model transporters (vehicles, such as trucks, forklifts, container carriers , etc.), which move material in discrete parcels

• a Conveyor module is used to model conveyors (continuous-mode conveyance facilities, such as conveyor belts)

Transporter and Conveyor Modules


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• In order to implement transporters or conveyors, the modeler specifies a transportation network consisting of

• locations (Station modules) • topology (distances among locations)

• Network topology is specified in

• Distance (data) modules (for transporters) • Segment (data) modules (for conveyors)

• Once the velocities of transports and conveyors are known, Arena will automatically compute the corresponding travel times

The Arena Transportation Network


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• When an Arena entity gets hold of a transporter, • the entity enters a Transport module for the duration of the transportation activity• the entity and the transporter move as a group

• When the group (entity and transporter) arrives at its destination Station module,

• the entity frees the transporter (possibly after a delay for unloading), and exits the Transport module• the transporter will stay at that Station module until requested again

• when an entity accesses a conveyor• the entity enters a Convey module for the duration of the conveyance activity• during the conveyance activity, the entity occupies a number of cells on the conveyor

• On arrival at its conveyance destination Station module, • the entity exits the conveyor and releases the conveyor cells it had occupied before, and exits the Convey module.

Transportation Rules of Operation


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• A number of additional modules regulate the operation of transporters and conveyors

• the Free module is used to release a transporter engaged by an entity• the Exit module is used to release a conveyor engaged by an entity• the Activate module is used to start transporters • the Halt module is used to stop transporters • the Start module is used to start conveyors• the Stop module is used to stop conveyors

• the Move module is used to advance a transporter among stations

Additional Transportation Modules


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• The Animate Transfer toolbar supports visualization and animation of various transportation devices, such as transporters and conveyors

• This toolbar’s buttons are shown below

Animate Transfer Toolbar

The Arena Animate Transfer toolbar


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• The Animate Transfer toolbar buttons are (left to right):1. The Storage button is used to animate the contents of a storage, similarly to the Queue button of the Animate toolbar. Internally, the Store and Unstore modules (from the Advanced Process template panel) provide the functionality of entities entering and departing a storage, while the number of entities in storage is accessible in the SIMAN variable NSTO(storage)

2. The Seize button allows the modeler to define a so-called seize area to animate entities seizing a resource.

3. The Parking button allows the modeler to define a so-called parking area to animate parking area for transporters.

4. The Transporter button allows the modeler to design a visual representation (picture) for a transporter.

5. The Station button permits the specification an icon for Station module.

Animate Transfer Buttons


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6. the Intersection button permits the specification of an intersection in a network of automated guided vehicles (AGVs), which are transporter- type objects that must keep track of their positions to avoid collisions

7. The Route button is used to specify the animation path for moving entities in the system

8. The Segment button is used to specify the animation path of a conveyor

9. The Distance button is used to specify the animation path of a transporter

10. The Network button is used to specify the animation path of an AGV

11. The Promote Path button is used to promote a visual line to an animation path of a desired object

Animate Transfer Buttons (Cont.)


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• This example models bulk port operations, using the notions of• station• entity routing among stations• entity pick-up and drop-off by another entity • the control of entity movements using logical gating

• The example models a bulk port, called Port Tamsar, where• the port operates continually 24 hours a day and 365 days a year• it has a single berth where the vessels dock, and a single ship loader • cargo vessel movements in the port are governed by tugboats

• We wish to simulate Port Tamsar for 1 year (8760 hours) and to estimate

• berth and ship-loader utilization• expected port time per ship

• Modeling accuracy of operations at Port Tamsar• a number of operating details have been omitted to simplify modeling• still, the foregoing description is quite realistic and applicable to many bulk-material ports and container ports around the world

Example: A Bulk Port Model


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TugboatStation

0.5 hour

Tugboat

OffshoreShip

Anchorage

1 hour

Coal-LoadingBerth

ShipLoader

CoalPile

1 hour

Layout of Port Tamsar


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• Ship arrivals are governed by the following rules of operation:• while the annual coal production plan calls for nominal deterministic ship arrivals at the rate of 1 ship every 28 hours, ships usually do not arrive on time due to weather conditions, rough seas, or other reasons, and consequently, each ship is given a 5-day grace period commonly referred to as the lay period • ships are assumed to arrive uniformly in their lay periods• arriving ships queue up FIFO (if necessary) at an offshore anchorage location, whence they are towed into port by a single tugboat as soon as the berth becomes available

Port Tamsar Ship Arrivals


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• Tugboats are governed by the following rules of operation:• the tugboat is stationed at a tug station located at a distance of 1/2 hour away

from the offshore anchorage

• travel between the offshore anchorage and the berth takes 1 hour

• it is assumed that there is an uninterrupted coal supply to the ship loader at

the coal-loading berth

• it is assumed that ship loading times are uniformly distributed between

14 and 18 hours

• once a ship is loaded at the berth, the tugboat tows it away to the offshore

anchorage, whence the boat departs with its coal for its destination

• higher priority is given to departing vessels in seizing the tugboat

Port Tamsar Tugboat operations


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• An important environmental factor in many port locations around the world is tidal dynamics

• cargo ships are usually quite large and need deep waters to get into and out

of port

• water depth increases with high tide and decreases with low (ebb) tide

• the time between two consecutive high tides is precisely 12 hours

• assume that ships can go in and come out of port safely only during

tidal window consisting of the middle 4 hours of high tide

• thus, every 12 hours, the tidal window at the port is closed for 8 hours

and open for 4 hours

Port Tamsar Tide Dynamics


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Arena model segment implementing ship arrivals at Port Tamsar

Vessel Arrivals

Check Tide_1for Tug BoatInbound Wait

Get Berth

Lay PeriodTime

Mark Arrival

0

Modeling Ship Arrivals


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• The Arena model segment implementing ship arrivals has the following logic:

• ship arrivals are generated deterministically by the Create module, called Vessel Arrivals, one ship every 28 hours• on creation, a ship entity immediately proceeds to the Delay module, called Lay Period, where it is delayed uniformly between 0 and 120 hours to model an actual arrival within its lay period• in due time, the ship entity enters the Assign module, called Mark Arrival Time, where its (actual) arrival time is stored in its

ArrTime attribute

Modeling Ship Arrivals (Cont.)


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Ship Arrivals Modules

Dialog box of the Seize module Get Berth


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Dialog box of the Hold module Check Tide_1

Ship Arrivals Modules (Cont.)


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Ship Arrivals Modules (Cont.)

Dialog box of the Hold module Inbound Wait for Tug Boat


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Tug Station

Create Tug

TugboatMonitor Need for

VesselPickup Inbound

VesselGo to Inbound

StationGo to Loading

Port Exit Station

Original

Members

Departing VesselDropoff

Dispose

Tally Port Time

Who Wants Tug BoatTrue

False

Vessel StationGo to Departing

0

0

0

0

Modeling Tugboat

Operation

Arena model segment implementing tugboat operations at Port Tamsar


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• The Arena model segment implementing tugboat operation has the following logic:

• at time 0, a single tugboat is created at the Create module, called

Create Tug• the tugboat then proceeds to the Station module, called Tug Station,

which merely serves as an entry point in the model• the tugboat immediately proceeds to the Hold module, called

Monitor Need for Tugboat, to monitor and wait for service “requests”• the ship entity waits in the queue Inbound Wait for Tug Boat.Queue

until the tugboat becomes available• the tugboat segment will ensure that the tugboat constantly monitors

the queue Inbound Wait for Tug Boat.Queue for ships waiting to be

towed into port

Modeling Tugboat Operation (Cont.)


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Tugboat Operation Modules

Dialog box of the Create module Create Tug


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Tugboat Operation Modules (Cont.)

Dialog box of the Station module Tug Station


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Dialog box of the Hold module Monitor Need for Tugboat


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• The logic of the Hold module, called Monitor Need for Tugboat, accomplishes the following functions:

• via the Condition field, the tugboat entity constantly monitors two queues,

Inbound Wait for TugBoat.Queue and Outbound Wait for

tugBoat.Queue,

for ships calling on its services • the monitored condition is the logical expression

NQ(Inbound Wait for Tug Boat.Queue) +

NQ(Outbound Wait for Tug Boat.Queue) > 0

which scans for ship entities waiting for the tugboat in either of the Hold

module’s queues housing inbound or outbound ships• once the scan condition becomes true, the tugboat will immediately

proceed to the Decide module, called Who Wants Tug Boat,

to find out if the request is from an inbound ship or a (high priority)

outbound ship



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Dialog box of the Decide module Who Wants Tug Boat


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Dialog box of the Route module Go to Departing Vessel Station


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Dialog box of the Pickup module Pickup Inbound Vessel


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• The logic of a Pickup module accomplishes the following functions:

• generally, a Pickup module is used by an incoming entity to pick up

other entities residing in a queue• the number of entities to be picked up is specified in the Quantity field,

starting from the queue position specified in the Starting Rank field• the queue itself is specified in the Queue Name field• the picking entity and the picked-up entities form a grouped entity,

where the picked-up members form an internal queue,

and are identified by their rank (position) in it• since the picking entity may make several pickups (at different times or

places), picked-up members of the group maintain their identity ID via

their rank• rank information may be used in entity drop-off



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Dialog box of the Route module Go to Loading Station


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Modeling Coal Loading

Arena model segment implementing coal loading at Port Tamsar


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Coal Loading Modules

Dialog box of the Station module Coal Loading Station


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Dialog box of the Dropoff module Dropoff Inbound Vessel

Coal Loading Modules (Cont.)


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Dialog box of the Seize module Seize Loader



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Dialog box of the Release module Release Loader and Berth



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Dialog box of the Pickup module Pickup Vessel



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Dialog box of the Hold module Check Tide_2



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Dialog box of the Record module Tally Port Time



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Modeling Tidal Windows

Arena model segment implementing tidal windows at Port Tamsar


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Tidal Windows Modules

Dialog box of the Create module Create Tidal Window


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Dialog box of the Assign module Close

Tidal Windows Modules (Cont.)


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Port Tamsar Simulation Results


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Port Tamsar Simulation Results (Cont.)


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Port Tamsar Simulation ResultsFor model with a shorter lay periods


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• This example models a toll plaza system on the New Jersey Turnpike, consisting of

• 2 exact-change (EC) lanes• 2 cash-receipt (CR) lanes • 1 Easy Pass (EZP) lane

• The layout of the toll plaza is shown below Toll

Booths

Exact Change(EC) Lanes

EZ Pass(EZP) Lane

Cash Receipt(CR) Lanes

Incoming Cars to Toll Plaza

Example: A Toll Plaza Model


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• Arriving vehicles select lanes (no jokeying allowed) as follows:1) 50% of all arriving cars go to EC lanes, and their service time distribution is (only the non-negative values are used) 2) 30% of all arriving cars go to CR lanes, and their service time distribution is 3) 20% of all arriving cars go to the EZP lane, and their service time distribution is

• Traffic congestion is non-stationary (heavier during morning and evening rush hours and lighter during off-peak hours) as follows:

4.81,1.01Norm( )

5 4.67,2.26Logn( )+

1.18 4.29× 2.27,3.02Beta( )+

Toll Plaza Car Arrivals and Service

8 4.4, 4.12Gamm( )+

1.32, 1.57, 1.76Tria( )

2.64 0.82, 4.5Weib( )+

1.32, 1.57, 1.76Tria( )

4.2 0.87, 8.24Gamm( )+

Time Period(in hours)

Inter Arrival Time Distribution (in seconds)

0 AM– 6 AM

6 AM – 9 AM

9 AM – 16 PM

16 PM – 19 PM

19 PM – 24 PM


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• The number of operating cash-receipt booths varies over time as follows:

• since such booths must be manned, and therefore are expensive to operate,

one of them is closed during the off-peak hours• only during morning and evening rush hours do all cash-receipt booths remain open

Toll Plaza Cash-Receipt Booths


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• Performance analysis objectives for the toll plaza system address the following issues:

1. What would be the impact of additional traffic on car delays?2. Would adding another booth markedly reduce waiting times?3. Could some booths be closed during some light traffic hours without appreciably increasing waiting times?4. What would be the impact of converting some cash-receipt booths to exact-change booths or to easy pass booths? 5. How would waiting times be reduced if both cash-receipt booths were to be kept open at all times?

• We wish to address the last issue above, using the following performance metrics

• average time to pass through the system • booth utilization

Toll Plaza Performance Issues


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Modeling Car Arrivals


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Car Arrivals Modules

Dialog box of the Create module Cars Arriving


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Dialog box for specifying sampling distributions (top) for time-dependent inter-arrivals in vector Int_Times (bottom)

Car Arrivals Modules (Cont.)


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Dialog box of the Assign module Assign Type and Modify Congestion Period



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Dialog box of the Decide module Which Type



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Dialog box of the Station module set for EC tollbooths



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Dialog box of the PickStation module Exact Change Cars



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Dialog box of the PickStation module Cash Receipt Cars



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• In the PickStation module, called Cash Receipt Cars,• while tollbooth CR_1 is open, then 1-MR(CRS_1) = 0, and the expression for CR_1 evaluates to NQ(CRSQ_1), so that the tollbooth selection will be made based on the minimum of NQ(CRSQ_1) and NQ(CRSQ_2), as required• conversely, while tollbooth CR_1 is closed, then 1-MR(CRS_1) = 1 and NQ(CRSQ_1) = 0, and the expression for CR_1 evaluates to 1000, and since this number exceeds NQ(CRSQ_2) by assumption, tollbooth CR_2 is sure to be selected, as required



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Car Services Modules

Dialog box of the Seize module Proceed to EC Booth


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Dialog box of the resource set EC Servers

Car Services Modules (Cont.)


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Dialog box of the spreadsheet views of sets in the Set module (bottom) and of the members of resource set EC Servers (top)



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Dialog box of the spreadsheet views of sets in the Set module (bottom) and of the members of resource set EC Servers (top)



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Dialog box of the Delay module Pay Exact Change



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Dialog box of the spreadsheet views of capacity schedules in the Schedule module (bottom)

and corresponding durations of server CRS_1 at the tollbooth CR_1 (top)



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Dialog box of the Release module Leave EC Booth



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Dialog box of the Record module Record Flow Times



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Toll Plaza Simulation Results


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Toll Plaza Simulation Results (Cont.)


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Toll Plaza Simulation Results (Cont.)


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• The dramatic impact of the closure of tollbooth CR_1 during off-peak hours leaves room for improvement

• to what extent would the flow times of CR cars be improved, if tollbooth CR_1 were to remain open at all times?

• It is easy to modify the tollbooth plaza Arena model to reflect this improved operating rule

• merely set the capacity of server resource CRS_1 to 1 at all times

• Simulation results show next the extent of the corresponding performance improvement

Improved Toll Plaza System


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Improved Toll Plaza Simulation Results


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Example: A Gear Job Shop Model• This example models a gear job shop consisting of

• an arrival dock• a milling station with 4 milling machines• a drilling station with 3 drilling machines• a paint shop with 2 spray booths• a polishing area with a single worker• a shop exit

• Gear types are G1, G2, G3 with distinct operations plans (sequences) • The layout of the job shop and gear sequences are shown below

DrillingStation

ArrivalDock

MillingStation

ShopExit

PaintingStation

PolishingStation

G1G2G3


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• The table below lists the job shop locations and their distances

Distances Among Job Shop Locations

FromLocation

ToLocation

Distance(in feet)

Arrival Dock Milling Station 100Arrival Dock Drilling Station 100

Milling Station Drilling Station 300Milling Station Paint Shop 400Milling Station Polishing Area 150

Paint Shop Polishing Area 300Drilling Station Paint Shop 150Drilling Station Polishing Area 400

Paint Shop Arrival Dock 250Polishing Area Arrival Dock 250Polishing Area Shop Exit 200

Shop Exit Arrival Dock 550Shop Exit Drilling Station 500Shop Exit Milling Station 300Shop Exit Paint Shop 400Shop Exit Polishing Area 200


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Gear Operations Plans• The table below lists the gear operations plans

GearType

OperationsSequence

Processing Times

(in minutes)

G1 Milling 35Drilling 20Painting 55Polishing 15

G2 Milling 25Painting 35Polishing 15

G3 Drilling 18Painting 35Polishing 15


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• The following statistics are of interest:• gear flow times (by type)• gear delays at production stations • machine utilizations

• To analyze the performance of the job shop, we plan to run a simulation over 1 year of operation

Gear Job Shop Performance Issues


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Gear Arrivals and Departures Models

Arena model segment implementing gear arrivals at the arrival dockand transport to the job shop floor

Arena model segment implementing gear transport from the job shop floor to the shop exit and flow time statistics collection


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Job Shop Floor Manufacturing Model


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Gear-Job Arrivals Modules

Dialog box of the Create module Create Jobs


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Gear-Job Arrivals Modules (Cont.)

Dialog box of the Assign module Assign Job Type and Sequence


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Dialog boxes of spreadsheet views of sequences in a Sequence module (bottom), operations steps of type G1 gears (middle)

and milling time assignment of type G1 gears (top)


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Dialog box of the Request module Request a Truck


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Dialog box of the Transport module Transport to Shop Floor


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Dialog box of the Free module Free Truck at Mill


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Gear-Job Service Modules

Dialog box of the Process module Milling


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Gear-Job Service Modules (Cont.)

Dialog box of the Request module Request Truck at Milling


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Dialog box of the Record module Tally Flow Time


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Dialog box of the Transporter spreadsheet module (bottom) and the dialog box of the Initial Position Status field (top)


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Dialog box of the Distance spreadsheet module (left) and the dialog box of its Stations field (right)


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Job Shop Simulation Results


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Job Shop Simulation Results (Cont.)


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• To reduce the wait at the paint shop, modify the job shop model by increasing the number of paint booths from 2 to 3

• The simulation results of the modified job shop are shown below

Modified Job Shop Model

Ch 12 Transport

Documents

tidal windows

job service

car arrivals

car services

job arrivals

type g1 gears

coal loading

service time