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Material Transport Lecture Slide
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Material Transport Systems
Chapter 10
Objectiveso By end of the class,
students should be able to:o Describe the five transport
system that are commonly used in manufacturing
o Explain characteristics of AGV (Guidance and traffic controls)
o Explain characteristics of conveyors
o Perform engineering analysis on material transport system
Material Transport systemo Needed to transport
materials (raw material, finished goods, WIP..etc) within manufacturing facilities and to/from warehouse or storage areas.
Common Material Handling Equipment
Equipment Features Typical Application
Industrial truck (manual or powered)
Low to medium cost, low rate of deliveries/hr
Moving light loads and palletized containers
Automated guided vehicles system
High cost, flexible routing
Moving pallet loads and WIP
Monorails and other rail guided vehicles
High cost, flexible routing
Moving single assemblies or large qty
Conveyors Various types Moving product in manufacturing lines
Cranes and hoist High lift capacity Moving large, heavy items in factories
Industrial Trucks
(a) Two-wheel hand truck, (b) four-wheel dolly, (c) hand-operated low-lift pallet truck
Automated Guided Vehicleso AGVS is a material handling
system that uses independently operated, self-propelled vehicles guided along a defined pathways.
o Appropriate where different materials are moved from various load points to various unload points.
Application of AGVs
Unit load carrier and pallet trucks: Used in storage and distribution and Flexible manufacturing system
Driver-less train: Used in moving large quantity of materials over large distances
Vehicle Guidance Technology
Self Guided Vehicles: Operated without defined pathways but with beacons located throughout the facilities. Pathway can be changed by changing the navigation data.
Imbedded guide wires : Guided by equal intensity of electromagnetic field on two sensors.
Paint strips: Guided by optical sensors
Vehicle Management & Safetyo Traffic Controls:
o Onboard sensors o Vehicle will stop upon detecting
obstacleo Sensors can be optical or ultrasonic
o Zone controlso Operating rules that no vehicle will
enter the zone if there is already occupied by another vehicles
o Safetyo Speeds normally slower than walking
paceo vehicle automatic stop if it strays more
than a short distance from specified path
o Emergency bumper-the vehicle automatically stop if the bumper is activated.
Conveyor Types
Roller and skate wheel conveyor Belt conveyor
Chain conveyor
(a) Single direction conveyor
(b) Continuous loop conveyor
Conveyor Types
Conveyor Operation & Features
o Powered conveyor can be divided into two:o Continuous conveyor moving
at constant velocityo Asynchronous conveyor
operating with a stop and go motion. Used :oAs buffersoTo allow differences in
production rate between adjacent process
oTo accommodate different conveyor speed
Monorails/Other railed guided vehicles
Crane and Hoists
Analysis of Material Transport System
o Based on MHI assumptions.o Focuses on 3 areas:
o Charting techniqueso Analysis of vehicle based
systemo Conveyor Analysis
Charting Techniqueso Purpose is to display the
material flowso Two techniques:
o From-To Chart
From-To-Chart
To 1 2 3 4 5
From
1 0 9/50* 5/120 6/205 0
2 0 0 0 0 9/80
3 0 0 0 2/85 3/170
4 0 0 0 0 8/85
5 0 0 0 0 0
Note: loads/hr /Travel Distance
Flow Diagram
1
4
3
2
5
9/50
9/806/205
8/852/85
3/170
5/120
Analysis of Vehicle Based Systems
o Assumption:o Vehicle operates at constant
velocity ignoring acceleration and deceleration,
o The time for typical delivery:o Loading at pick up station, o Traveling time to drop off
stationo unloading at drop off station,o empty traveling time of the
vehicleo Therefore:
LT
LT
UT
d ec L U
c e
L LT T T
v v
o can be used to calculate: o Hourly rate of deliver per
vehicle, o AT depends on
o Availability of the vehicles, Ao Traffic congestion, Tf
o Efficiency of manual driver, Eo Therefore
Analysis of Vehicle Based Systems
cT60
dvc c
ATR
T T
60 fAT AT E
Analysis of Vehicle Based Systems
o Number of vehicles required to satisfy specified delivery requirement,Rf
o Total workload
o Number of required vehiclesf cWL R T
fc
dv
RWLn
AT R
Example 1An automated guided vehicle system has an average travel distance per delivery = 200 m and an average empty travel distance = 150 m. Load and unload times are each 24 s and the speed of the AGV = 1 m/s. Traffic factor = 0.9. How many vehicles are needed to satisfy a delivery requirement of 30 deliveries/hour? Assume that availability = 0.95 and worker efficiency = 1.0.
Example 2Four forklift trucks are used to deliver pallet loads of parts between work cells in a factory. Average travel distance loaded is 350 ft and the travel distance empty is estimated to be the same. The trucks are driven at an average speed of 3 miles/hr when loaded and 4 miles/hr when empty Terminal time per delivery averages 1.0 minute (load = 0.5 minute and unload = 0.5 minute). If the traffic factor is assumed to be 0.90, availability = 100%, and worker efficiency = 0.95, what is the maximum hourly delivery rate of the four trucks? (1mile=5280 ft)
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