Chapter 7 Automated MaterialHandling and Storage Systems

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Chapter 7Automated Material-Handling and Storage
Systems
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Agenda

• Material Handling System
• Automated Guided Vehicle Systems
• Automated Storage and Retrieval Systems
• Distributed Computer Control Architecture for
  AGVSs and AS/RSs
• Conveyors

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Material Handling System

• Definition an integrated system involving such
  activities as handling, storing, and controlling
  of materials
• Objectivematerial in the right amount is safely
  delivered to the desired destination at the right
  time and at minimum cost
• Principles of Material Handling 20 guidelines
  for designing and operating material-handling
  systems (reading). E.g. unit load principle,
  space utilization principle, etc.
• Material-handling equipments industrial trucks,
  conveyors, AGVSs, AS/RSs, and others (monorails,
  cranes, hoists, etc.)

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Automated Guided Vehicle Systems

• Definition an AGVS is a battery-powered
  driverless vehicle with programming capabilities
  for destination, path selection, and positioning
• Materials loading locations ? unloading
  locations
• Collision avoidance capability
• Communication wire in the floor, radio
• Components
• The vehicle
• The guide path
• The control unit
• The computer interface

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Types of AGVs
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Automated Guided Vehicle Systems

• Management of AGVSs
• AGVS guidance systems low cost change, flexible.
  Selection need, application, environment
  constraints
• Wire-guided guidance system energized wire, the
  antenna
• Optical guidance system colorless flourescent
  particles, photosensors, clean operating
  environment
• Inertial guidance system a microprocessor, a
  sonar system, a gyroscope
• Infrared guidance system infrared light
  transmitters, reflectors, radar-like detectors,
  computer
• Laser guidance system a laser beam, bar-coded
  detectors
• Teaching-type guidance system use neural
  network concepts to learn the path

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Automated Guided Vehicle Systems

• Management of AGVSs (cont.)
• AGVS steering control control the turn and
  maneuvering.
• Differential-speed steer control balancing the
  amplitudes of the left and right signals, less
  tracking tolerance
• Steered-wheel steer control detect the positive
  or negative phase of the sensor signal received
  from the guided path wire, high tolerance
• AGVS routing to take the shortest path
• Frequency select method
• Path-switch select method

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Automated Guided Vehicle Systems

• Management of AGVSs (cont.)
• AGVS control systems
• Computer-controlled system most efficient,
  expensive and complex.
• Remote dispatch control system operator uses a
  remote control station to send instructions
  directly to the vehicle. Automatic load/unload
• Manual control system operator load/unload and
  enters instructions on the vehicle
• Interface with other subsystems
• Subsystems AS/RS, FMS, CNC machines, process
  control equipment, shop floor control system
• Methods Distributed data processing network,
  host computer
• AGVS load transfer loading and unloading
  operations
• Manual load transfer coupling and uncoupling
  towed trailers, by folk lift truck, by roller,
  manual loading/unloading
• Automatic load transfer automatic
  couple/uncouple powered roller, belt, chain
  powered lift and lower device powered push or
  pull device

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Automated Guided Vehicle Systems

• AGVS design features common features to
  material-handling and special features must be
  considered in the design of AGVSs
• Stopping accuracy depend on the applications,
  e.g. 0.001 inch for machine tool interfaces
• Facilities automatic door-opening devices,
  elevators, environmental compatibility
• Safety emergency contact bumpers and stop
  buttons, automatic warning signals, etc.
• Maintenance service manual, Preventive
  maintenance (intervals replacement,
  condition-based checking)

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Automated Guided Vehicle Systems

• System design of AGVSs
• Attributes for selection of guidance and AGVS
• Methods MCDM, ranking approaches
• Groups of attributes (reading) the vehicle,
  vendor support and services
• Steps choose a feasible set of AGV models based
  on attribute values ? rank
• Flow path design often use simulation, determine
• The type of guidepath layout application
• The type of flow path within the layout
  controls, economic
• The number and location of load transfer points
  (P/D station)
• Load transfer station storage space
• Number of AGVs required
• Total time/delivery/vehicle
• Number of deliveries/vehicle/h
• Number of AGVs Ndr/Nd
• Where Dd(De) total av. loaded (empty) travel
  distance Ndr no. of deliveries required/hr Th
  loading and unloading time Tf traficfactor
  (0.85 - 1) v vehicle speed

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Example 1
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Automated Guided Vehicle Systems

• Advantages of AGVSs
• Flexibility
• Higher reliability
• Higher operating savings and lower investment
• Unobstructed movements
• Easy interfacing with other systems
• Applications of AGVSs
• Raw material storage
• Finished goods storage
• Assembly operations
• FMSs
• Manufacturing operations

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Applications
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Automated Storage and Retrieval Systems (AS/RSs)

• Definition an AR/RS system is a combination of
  equipment and controls which handles, stores and
  retrieves materials with precision, accuracy and
  speed under a defined degree of automation
• Functions An RS/RS attempts to achieve
  automatically the storage functions in
  cost-effective and efficient manner
• Operations
• Automatic removal of an item from a storage
  location
• Transportation of this item to a specific
  processing or interface point
• Automatic storage of an item in a predetermined
  location, having received an item from a
  processing or interface point

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AS/RS Components

• A series of storage aisles having storage racks
• S/R machines
• One or more pickup and delivery stations

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Why an AS/RS?

• Highly space efficient
• Increased storage capacity to meet long-term plan
• Improved inventory management and control
• Quick response time to locate, store, and
  retrieve items
• Reduced shortages of inventory items due to
  real-time information and control
• Reduced labor costs
• Improved stock rotation
• Improved security and reduced pilferage
• Flexibility in design to accommodate a wide
  variety of loads
• Flexibility in interfacing with other systems
• Reduced scrap and rework
• Reduced operating expenses for light power, heat
• Helps implement JIT concepts.

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Types of AS/RS

• Unit load AS/RS standard-size containers, loadgt
  500lb/unit, computer controlled, automatic S/R
  machines guided by rails
• Mini-load AS/RS small loads, small investment
• Person-on-board AS/RS operator rides on a
  platform with S/R to pick up items
• Deep-lane AS/RS variation of unit load,
  multi-deep storage, flow-through rack. Load S/R
  machines ? rack-entry vehicle ( a platform)
  ?storage rack
• Automated item retrieval system flow-through,
  storerear, retrieve-front

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Design of an AS/RS

• Determining load sizes dimensions of the unit
  load (h,l,w) with appropriate clearance
  (c1,c2,c3)
• Determining the dimensions of an individual
  storage space
• Height of a storage space h c1
• Length of a storage space l c2
• Width of a storage space u(wc3),
• Normally, the storage space depth (width) u 3
  unit loads
• Example2 Determine the size of a single storage
  space. Dimension of a unit load are 48(w)
  x52(l)x52(h). The clearances are
  c110in.c28in.,c3 6in., and u 3
• Solution high 52 10 62 in.
• length 52 8 60 in.
• width 3(48 6) 162 in.

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Design of an AS/RS

• Determining the number of storage spaces
• Dedicated storage (fixed-slot storage) policy
  each product ? set of slots. Number of slots
  ?maximum inventory levels for all the products
• Randomized storage policy (floating-slot)
  probability of S/R are the same for very slot/
  product unit. Number of slots max aggregate
  inventory level of all products

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Example 3
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Design of an AS/RS

• Determining the system throughput and the number
  of S/R machines
• The system throughput the number of loads to be
  stored and number of loads to be retrieved/hour
• Speed of S/R machine
• Mix of single- and dual- cycle transaction
• percent utilization of storage racks
• Arrangement of stored items
• AS/RS control system speed
• Speed and efficiency of the material-handling
  equipment used to move loads to the input and
  remove loads from the output
• Number of S/R machines (system throughput)/
  (S/R machine capacity in cycles/h)
• Example 4 suppose the single command cycle
  system for the S/R machine is recommended. The
  average cycle time per operation is 1min. The
  desired system throughput is 360 operations/h. An
  operation refers to either storage or retrieval
  and both take approximately the same time.
  Determine the number of S/R machines
• Solution number of cycles/h/machine 60, number
  of machines 6

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Design of an AS/RS

• Determining the size parameters of the S/R system
  (length, width, height)
• Determining the number of rows and number of bays
  in each row if one machine ? one aisle
• Number of rows 2 x number of S/R machines
• Number of bays (no. of required storage
  spaces)/(no. of rows/machine x no.of machines x
  no. of storage spaces/ system height)
• Number of storage spaces/system height desired
  system height /storage space height desired
  system height 30 90ft
• Determining bay width, rack length, system
  length, bay depth, aisle unit, and system width
• Bay width length of a storage space
  center-to-center rack support width (l c2)
  c4
• Rack length bay width x number of bays
• System lengthrack lengthclearance for S/R
  machineclearance for the P/Darea
• Bay depth width of individual storage space
  bay side support allowance u(w c3) c5
• Aisle unit aisle width (2 x bay depth)
• System width aisle unit x desired number of
  aisles

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Example 4
Using the data from examples 2 and 3, determine
the number of rows and the number of bays in each
row in the system
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2
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Example 5
2,3 and 4
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Design of an AS/RS

• Determining single- and dual-command cycle times
  for unit load AS/RS
• Single-command cycle either a storage or
  retrieval operation is performed, but not both.
  Storage/retrieval cycle is assumed to begin with
  the S/R machine at the P/D station
• Dual-command cycle assume to begin with the S/R
  machine at the P/D station
• Assumptions
• Randomized storage policy
• Constant horizontal and vertical velocities
• Single-sized rack openings
• P/D station located at the base and at the end of
  the aisle
• S/R machine travels simultaneously in the aisle
  both horizontally and vertically

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Design of an AS/RS

• Determining single- and dual-command cycle times
  (cont.)
• Time required to travel the full horizontal
  length and vertical height of an aisle
• th L/Vh n(l c2)/Vh and tv H/Vv m(h
  c1)/Vv
• Single-command cycle time
• Dual-command cycle time
• Where L, H length, height of an aisle
• n, m number of bays, storage spaces/system
  height
• Vh, Vv average horizontal, vertical speeds of
  S/R machines
• T max(th, tv) and Q min(th/T, tv/T)
• Tpd time to perform either a pick up or deposit

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Example 6
Johnson and Johnson has a unit load AS/RS with 6
aisles. Six S/R machines are used, one for each
aisle. From example 5, the aisle length (rack
length) is 275ft and aisle height is 77.5ft. The
horizontal and vertical speeds are 300ft/min and
70ft/min, respectively. A P/D operation of the
S/R machine takes approximately 0.35min.
Determine the single and dual command cycle times
for a unit load AS/RS of JJ company
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Design of an AS/RS

• Determining the utilization of S/R machines
• The number of transactions/(S/R machine)/h
• nt ST /N
• Where
• ST system throughput (no. loads to be stored
  and retrieved/h)
• N number of S/R machines (one machine, one
  aisle)
• The workload/(S/R machine) ?ntTsc ?(nt/2)Tdc
  (min/h)
• Where ? percentage of operations done by sc
  cycles
• ? percentage of operations done by
  dc cycles
• number of storages number of
  retrievals in long run

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Example 7
Suppose the system throughput is 300 storage and
retrievals per hour. The AS/RS has 10 aisles and
each is served by one S/R machine. Furthermore,
30 of the operations are performed as
single-command and the rest as dual-command
operations. Determine the utilization of the
machine. Other data from example 6 apply to this
problem. Determine the number of transactions at
which the S/R machine is 100 utilized
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Distributed Computer Control Architecture for
AGVSs and AS/RSs

• Central control and distributed control? control
  the flow of materials and information
• Objective ensure the automated systems keep
  running even if a control component fails
• Distributed control system for integration of
  various components (AGVS, AS/RS, FMS)
• Advantages
• Maintenance at level
• No large central computer
• Flexible expansion

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Conveyors

• A conveyor is a convenient and cost-effective
  means of moving materials over a fixed path
• Types of conveyor2 types according to
• type of product to be handle bulk or unit
• Location of the conveyor overhead or floor
• Conveyors are designed to meet specific
  application requirements