Introduction to Material Handling

• The handling of materials must be performed safely, efficiently, at low cost, in a timely manner, accurately (the right materials in the right quantities to the fight locations), and without damage to the materials.

• The cost of material handling is a significant portion of total production cost, estimates averaging around 20-25% of total manufacturing labor cost

Handling of materials must be Handling of materials must be performed performed • SafelySafely• EfficientlyEfficiently• At low costAt low cost• In a timely mannerIn a timely manner• Accurately (the right materials in the Accurately (the right materials in the

right quantities to the right locations)right quantities to the right locations)• And without damage to the materialsAnd without damage to the materials

Overview of material handling equipment:Material Transport Equipment:(a) Industrial trucks: Industrial trucks divide into two

types: non-powered and powered. Non-powered trucks are platforms or containers

with wheels that are pushed or pulled by human workers to move materials.

Powered industrial trucks are steered by human workers. They provide mechanized movement of materials.

(b) Automated guided vehicles: (AGVs). AGVs are battery-powered, automatically

steered vehicles that follow defined pathways in the floor.

AGVs are used to move unit loads between load and unload stations in the facility. Routing variations are possible, meaning that different loads move between different stations.

(c) Mono rails and other rail guided vehicles: These are self-propelled vehicles that ride on a

fixed rail system that is either on the floor or suspended from the ceiling.

The vehicles operate independently and are usually driven by electric motors that pick up power from an electrified rail.

Like AGVS, routing variations are possible in rail-guided vehicle systems.

(d) Conveyors: These are designed to move materials over

fixed paths, generally in large quantities or volumes.

Examples include- roller. belt and tow-line conveyors.

Conveyors can be either powered or non-

powered.

(e) Cranes and hoists: These are handling devices for lifting, lowering, and transporting materials, often as very heavy loads. Hoists accomplish vertical lifting; both manually operated and powered types are available. Cranes provide horizontal travel and generally include one or more hoists.

Design Considerations in Material Handling:

Design of the system depends on the materials to be handled, quantities and distances to be moved. Type of production facility served by the handling system, and other factors, including available budget.

• Material characteristics

• Flow rate, routing and scheduling

• Plant layout

Material characteristics:

Category Measures or Descriptors

Physical state

Solid, liquid or gas

size Volume, length, width, height

Weight Weight per piece, weight per unit volume

Shape Long and flat, round, square, etc

Condition Hot. Cold, wet, dirty, sticky

Risk of damage

Fragile, brittle, sturdy

Safety risk Explosive, flammable, toxic, corrosive, etc

Flow rate, routing and scheduling:In addition to material characteristics the other factors are (1) Quantities and flow rates of materials to be moved, (2) Routing factors, and (3) Scheduling of the moves.

Manual handlingHand trucks

Powered trucksUnit load AGV

Conveyors ConveyorsAGV trainHigh

Low

LongShort Move Distance

Quantity of material moved

Plant layout :Plant layout :

Plant layout is an important factor in the design of a material handling system. In the case of a new facility. the design of the handling system should be considered part of the layout design.

The plant layout design should provide the following data for use in the design of the handling system:

• Total area of the facility and areas within specific departments in the plant.

• Arrangement of equipment ill the layout, locations where materials must be picked up (load stations) and delivered (unload stations).

• possible routes between these locations, and distances traveled.

• Opportunities to combine deliveries and potential locations in the layout where congestion might occur must be considered.

Layout TypeLayout Type CharacteristicsCharacteristics Typical MH Typical MH EquipmentEquipment

Fixed – positionFixed – position

ProcessProcess

ProductProduct

Large product size, Large product size, low production ratelow production rate

Variation in Variation in product and product and processing, low processing, low and medium and medium production ratesproduction rates

Limited product Limited product variety, high variety, high production rateproduction rate

Cranes, hoists, Cranes, hoists, industrial trucksindustrial trucks

Hand trucks, Hand trucks, forklift trucks, forklift trucks, AGVsAGVs

Conveyors for Conveyors for product flow, product flow, trucks to deliver trucks to deliver components to components to stations.stations.

Material Transport Material Transport EquipmentEquipment

Five categories:Five categories:1.1. Industrial trucksIndustrial trucks

2.2. Automated guided vehiclesAutomated guided vehicles

3.3. Monorails and other rail guided vehiclesMonorails and other rail guided vehicles

4.4. ConveyorsConveyors

5.5. Cranes and hoistsCranes and hoists

Industrial Trucks:Industrial Trucks:

Two basic categories:Two basic categories:

1.1. Non-poweredNon-powered• Human workers push or pull loadsHuman workers push or pull loads

2.2. PoweredPowered• Self-propelled, guided or driven by Self-propelled, guided or driven by

humanhuman

• Common example: forklift truckCommon example: forklift truck

Non-powered Industrial Trucks(Hand Non-powered Industrial Trucks(Hand Trucks)Trucks)

(a) Two-wheel hand truck, (b) four-wheel (a) Two-wheel hand truck, (b) four-wheel dolly, dolly,

(c) hand-operated low-lift pallet truck(c) hand-operated low-lift pallet truck

Quantities of material moved and distances are relatively low when this type of equipment is used to transport materials

Powered TrucksThree common types are used in

factories and warehouses:• Walkie trucks,

• Forklift rider trucks,

• Towing tractors.

Walkie trucks: these are battery powered vehicles equipped

with wheeled forks for insertion into pallet openings but with no provision for a worker to ride on the vehicle.

Forklift rider trucksThese arc distinguished from walkie

trucks by the presence of a modest cab for the worker to sit in and drive the vehicle.

Capacities from 450 kg up to 4500 kg

Power sources include on-board batteries and internal combustion engines

Towing tractors

Designed to pull one or more trailing carts in factories and warehouses, as well as for airport baggage handling

Powered by on-board batteries or IC engines

Automated guided vehicle systems:An Automated Guided Vehicle System

(AGVS) is a material handling system that uses independently operated, self-propelled vehicles guided along defined pathways in the facility floor.

The vehicles arc powered by on-board batteries that allow many hours of operation (8-16 hr is typical) between recharging.

Types of AGVS:•Driverless trains

•Pallet trucks

•Unit load AGVs

Driverless Automated Guided Trains:• A driverless train consists of a towing vehicle (which

is the AGV) that pulls one or more trailers to form a train.

•Common application is moving heavy payloads over long distances in warehouses and factories without intermediate stops along the route

Automated guided pellet trucks:

• Used to move palletized loads along predetermined routes.

• Vehicle is backed into loaded pallet by worker; pallet is then elevated from floor

• Worker drives pallet truck to AGV guide path and programs destination

Unit Load Carrier :

• Used to move unit loads from station to station

• Often equipped for automatic loading/unloading of pallets and tote pans using roller conveyors, moving belts, or mechanized lift platforms

AGVs Applications

• Driverless train operations - movement of large quantities of material over long distances

• Storage and distribution - movement of pallet loads between shipping/receiving docks and storage racks

• Assembly line operations - movement of car bodies and major subassemblies (motors) through the assembly stations

• Flexible manufacturing systems - movement of workparts between machine tools

• Miscellaneous - mail delivery and hospital supplies

Vehicle Guidance Technology• Method by which AGVS pathways are defined and

vehicles are controlled to follow the pathways

• Three main technologies:

•Imbedded guide wires - guide wires in the floor emit electromagnetic signal that the vehicles follow

•Paint strips - optical sensors on-board vehicles track the white paint strips

•Self-guided vehicles - vehicles use a combination of

•Dead reckoning - vehicle counts wheel turns in given direction to move without guidance

•Beacons located throughout facility - vehicle uses triangulation to compute locations

Rail-Guided Vehicles:

• Self-propelled vehicles that ride on a fixed-rail system

• Vehicles operate independently and are driven by electric motors that pick up power from an electrified rail

• Fixed rail system

•Overhead monorail - suspended overhead from the ceiling

•On-floor - parallel fixed rails, tracks generally protrude up from the floor

• Routing variations are possible: switches, turntables, and other special track sections

Overhead Monorail:

Conveyor Systems

Large family of material transport equipment designed to move materials over fixed paths, usually in large quantities or volumes

1. Non‑powered • Materials moved by human workers or by

gravity

2. Powered • Power mechanism for transporting

materials is contained in the fixed path, using chains, belts, rollers or other mechanical devices

Conveyor Types:• Roller

• Skate‑wheel

• Belt

• In‑floor towline

• Overhead trolley conveyor

• Cart-on-track conveyor

Roller Conveyor:• Pathway consists of a series of rollers that are

perpendicular to direction of travel• Loads must possess a flat bottom to span several

rollers• Powered rollers rotate to drive the loads

forward• Un-powered roller conveyors also available

Skate-Wheel Conveyor:• Similar in operation to roller conveyor but

use skate wheels instead of rollers• Lighter weight and unpowered• Sometimes built as portable units that can

be used for loading and unloading truck trailers in shipping and receiving

Belt Conveyor:

• Continuous loop with forward path to move loads

• Belt is made of reinforced elastomer

• Support slider or rollers used to support forward loop

• Two common forms:

•Flat belt (shown)

•V-shaped for bulk materials

In-Floor Tow-Line Conveyor:

• Four-wheel carts powered by moving chains or cables in trenches in the floor

• Carts use steel pins (or grippers) to project below floor level and engage the chain (or pulley) for towing

• This allows the carts to be disengaged from towline for loading and unloading

Overhead Trolley Conveyor:• A trolley is a wheeled carriage running on

an overhead track from which loads can be suspended

• Trolleys are connected and moved by a chain or cable that forms a complete loop

• Often used to move parts and assemblies between major production areas

Cart-On-Track Conveyor:• Carts ride on a track above floor level

• Carts are driven by a spinning tube

• Forward motion of cart is controlled by a drive wheel whose angle can be changed from zero (idle) to 45 degrees (forward)

Powered Conveyor Operations and Features:

• Types of motions1. Continuous - conveyor moves at

constant velocity2. Asynchronous - conveyor moves with

stop-and-go motion They stop at stations, move between

stations

• Another classification of conveyors:1. Single direction2. Continuous loop3. Recirculating