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Chapter 7 Automated MaterialHandling and Storage Systems

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Title: Chapter 7 Automated MaterialHandling and Storage Systems


1
Chapter 7Automated Material-Handling and Storage
Systems
2
Agenda
  • Material Handling System
  • Automated Guided Vehicle Systems
  • Automated Storage and Retrieval Systems
  • Distributed Computer Control Architecture for
    AGVSs and AS/RSs
  • Conveyors

3
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.)

4
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

5
Types of AGVs
6
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

7
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

8
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9
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

10
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)

11
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

12
Example 1
13
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

14
Applications
15
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

16
AS/RS Components
  • A series of storage aisles having storage racks
  • S/R machines
  • One or more pickup and delivery stations

17
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.

18
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

19
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.

20
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

21
Example 3
22
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

23
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

24
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
3
2
25
Example 5
2,3 and 4
26
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

27
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

28
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
29
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

30
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
31
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

32
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
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