Material Transport Systems Chapter 10

Objectives By end of the class, students should be able to: Describe the five transport system that are commonly used in manufacturing Explain characteristics of AGV (Guidance and traffic controls) Explain characteristics of conveyors Perform engineering analysis on material transport system

Material Transport system Needed to transport materials (raw material, finished goods, WIP..etc) within manufacturing facilities and to/from warehouse or storage areas.

Common Material Handling 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 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 Vehicles AGVS is a material handling system that uses independently operated, self-propelled vehicles guided along a defined pathways. Appropriate where different materials are moved from various load points to various unload points.

Application of AGVs Driver-less train: Used in moving large quantity of materials over large distances Unit load carrier and pallet trucks: Used in storage and distribution and Flexible manufacturing system

Vehicle Guidance Technology Imbedded guide wires : Guided by equal intensity of electromagnetic field on two sensors. Paint strips: Guided by optical sensors Self Guided Vehicles: Operated without defined pathways but with beacons located throughout the facilities. Pathway can be changed by changing the navigation data.

Vehicle Management & Safety Traffic Controls: Onboard sensors Vehicle will stop upon detecting obstacle Sensors can be optical or ultrasonic Zone controls Operating rules that no vehicle will enter the zone if there is already occupied by another vehicles Safety Speeds normally slower than walking pace vehicle automatic stop if it strays more than a short distance from specified path Emergency bumper-the vehicle automatically stop if the bumper is activated.

Conveyor Types Belt conveyor Roller and skate wheel conveyor Chain conveyor

Conveyor Types (a) Single direction conveyor (b) Continuous loop conveyor

Conveyor Operation & Features Powered conveyor can be divided into two: Continuous conveyor moving at constant velocity Asynchronous conveyor operating with a stop and go motion. Used : As buffers To allow differences in production rate between adjacent process To accommodate different conveyor speed

Monorails/Other railed guided vehicles

Crane and Hoists

Analysis of Material Transport System Based on MHI assumptions. Focuses on 3 areas: Charting techniques Analysis of vehicle based system Conveyor Analysis

Charting Techniques Purpose is to display the material flows Two techniques: From-To Chart

From-To-Chart To 1 2 3 4 5 From Note: loads/hr /Travel Distance 9/50* 9/50* 5/120 6/205 9/80 2/85 3/170 8/85 Note: loads/hr /Travel Distance

Flow Diagram 9/50 2 1 9/80 6/205 5/120 3/170 3 5 2/85 4 8/85

Analysis of Vehicle Based Systems Assumption: Vehicle operates at constant velocity ignoring acceleration and deceleration, The time for typical delivery: Loading at pick up station, Traveling time to drop off station unloading at drop off station, empty traveling time of the vehicle Therefore:

Analysis of Vehicle Based Systems can be used to calculate: Hourly rate of deliver per vehicle, AT depends on Availability of the vehicles, A Traffic congestion, Tf Efficiency of manual driver, E Therefore

Analysis of Vehicle Based Systems Number of vehicles required to satisfy specified delivery requirement,Rf Total workload Number of required vehicles

Example 1 An 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 2 Four 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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