mm 323 man sys 2014 fall 1 introduction material handling systems.pdf

8/11/2019 MM 323 MAN SYS 2014 FALL 1 Introduction Material Handling Systems.pdf

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MM 323 MANUFACTURING SYSTEMS

MATERIAL HANDLING AND STORAGE SYSTEMS


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Material Handling

A means of moving and storing materials betweenprocessing and/or assembly operations

Material transport

Vehicles, e.g., forklift trucks, AGVs, monorails

Conveyors Hoists and cranes

Also used as storage systems

Unitizing equipment

Automatic identification and data capture (AIDC)

Bar codes

RFID

Other AIDC equipment


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Material Handling System

In most manufacturing systems that process or assemble

discrete parts and products, the following material

handling functions must be provided:

1. Loading work units at each station2. Positioning work units at each station

3. Unloading work units at each station

4. Transporting work units between stations in multi-station

systems

5. Temporary storage of work units


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Work Transport Between Stations

Two general categories of work transport in multi-stationmanufacturing systems:

1. Fixed routingWork units always flow through the same sequence of

workstations

Most production lines exemplify this category

2. Variable routingWork units are moved through a variety of different station

sequencesMost job shops exemplify this category


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(a) Fixed Routing and (b) Variable Routing


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Material Transport Equipment

Five categories:

1. Industrial trucks

2. Automated guided vehicles

3. Monorails and other rail guided vehicles

4. Conveyors

5. Cranes and hoists


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Industrial Trucks

Two basic categories:

1. Non-powered

Human workers push or pull loads

2. Powered

Self-propelled, guided or driven by human

Common example: forklift truck


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Nonpowered Industrial Trucks

(Hand Trucks)

(a) Two-wheel hand truck, (b) four-wheel dolly, (c) hand-operated low-lift pallet truck


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Unit Load Containers

(a) Wooden pallet, (b) pallet box, (c) tote box


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Powered Trucks:

Walkie Truck

Wheeled forks insert into pallet openingsNo provision for riding; truck is steered by worker

using control handle at front of vehicle


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Powered Trucks:

Forklift Truck

Widely used in factories and

warehouses because

pallet loads are so

commonCapacities from 450 kg

(1000 lb) up to 4500 kg

(10,000 lb)

Power sources include on-board batteries and

internal combustion

motors


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Powered Trucks:

Towing Tractor

Designed to pull one or more trailing carts infactories and warehouses, as well as for airport

baggage handling

Powered by on-board batteries or IC engines


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Automated Guided Vehicles

An Automated Guided Vehicle System (AGVS) isa material handling system that uses

independently operated, self-propelled vehicles

guided along defined pathways in the facility

floorTypes of AGV:

Driverless trains

Pallet trucks

Unit load AGVs


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Automated Guided Vehicles:

Driverless Automated Guided Train

First type of AGVS to be

introduced around

1954

Common application is

moving heavy

payloads over long

distances in

warehouses and

factories withoutintermediate stops

along the route


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AGV Pallet Truck

Used to move palletized

loads along

predetermined routes

Vehicle is backed intoloaded pallet by

worker; pallet is then

elevated from floor

Worker drives pallet

truck to AGV guide

path and programs

destination


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Unit Load Carrier

Used to move unit loads from station to station

Often equipped for automatic loading/unloading ofpallets and tote pans using roller conveyors,

moving belts, or mechanized lift platforms


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Overhead Monorail


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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


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Conveyor Types

Roller

Skate-wheel

Belt

In-floor towlineOverhead trolley conveyor

Cart-on-track conveyor


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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


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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 shippingand receiving


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Belt Conveyor

Continuous loop withforward path to moveloads

Belt is made of reinforced

elastomerSupport slider or rollers

used to support forwardloop

Two common forms:

Flat belt (shown)

V-shaped for bulkmaterials

(Support frame not shown)


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In-Floor Tow-Line Conveyor

Four-wheel carts powered by

moving chains or cables in

trenches in the floor

Carts use steel pins (orgrippers) 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


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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


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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)


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Powered Conveyor

Operations and Features

Types of motions

1. Continuous - conveyor moves at constant velocity

2. Asynchronous - conveyor moves with stop-and-go motion

They stop at stations, move between stations

Another classification of conveyors:

1. Single direction

2. Continuous loop

3. Recirculating


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(a) Single-Direction Conveyor and

(b) Continuous Loop Conveyor

(a) Single direction

conveyor

(b) Continuous loop

conveyor


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Cranes and Hoists

Handling devices for lifting, lowering and transporting

materials, often as heavy loads

Cranes

Used for horizontal movement of materials

Hoists

Used for vertical lifting of materials

Cranes usually include hoists so that the crane-and-hoist

combination provides

Horizontal transport

Vertical lifting and lowering


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Hoist

Hoist with mechanical

advantage of four:

(a) sketch of the hoist

(b) diagram to

illustrate mechanical

advantage

(a) (b)


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Gantry Crane

A half-gantry crane


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Jib Crane

EXAMPLES (A i li d t )


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EXAMPLES (An inclined conveyor system)

EXAMPLES (A h i d i )


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EXAMPLES (A chain drive conveyor)


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Time Spent in Material Handling


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Conventional Storage Methods

Bulk storage - storage in an open floor area

Problem: achieving proper balance between storage densityand accessibility

Rack systems - structure with racks for pallet loads

Permits vertical stacking of materialsShelving and bins - horizontal platforms in structural frame

Steel shelving comes in standard sizes

Finding items can be a problem

Drawer storage - entire contents of each drawer can beviewed


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Bulk Storage

Bulk storage arrangements:

(a) high-density bulk storage provides low accessibility,

(b) bulk storage with loads forming rows and blocks for improved accessibility

(c) Low cost per sq meter


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Pallet Rack System

Pallet loads placed on

racks in multi-rack

structure

(a) Low cost

(b) Good stroge density

(c) Good accessibility


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Automated Storage Systems

Mechanized and automated storage equipment to reducethe human resources required to operate a storage facility

Significant investment

Level of automation varies

In mechanized systems, an operator participates in each

storage/retrieval transaction

In highly automated systems, loads are entered or retrieved

under computer control


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Objectives and Reasons for

Automating Storage Operations

To increase storage capacity

To increase storage density

To recover factory floor space currently used for WIP

To improve security and reduce pilferage

To reduce labor cost and/or increase productivity

To improve safety

To improve inventory control

To improve stock rotation

To improve customer service

To increase throughput


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Types of Automated Storage System

1. Automated Storage/Retrieval System (AS/RS)

Rack system with mechanized or automated crane to

store/retrieve loads

2. Carousel Storage System Oval conveyor system with bins to contain individual items


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AS/RS

Unit load on

pallet AS/RS

with one aisle


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AS/RS Applications

1. Unit load storage and retrieval

Warehousing and distribution operations

AS/RS types: unit load, deep lane (food industry)

2. Order picking

AS/RS types: miniload, man-on-board, item retrieval

3. Work-in-process storage

Helps to manage WIP in factory operations

Buffer storage between operations with different production rates

Supports JIT manufacturing strategy Kitting of parts for assembly


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Horizontal Carousel Storage System

Manually operated

horizontal

carousel storage

system


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Carousel Applications

1. Storage and retrieval operations

Order picking

Kitting of parts for assembly

2. Transport and accumulation

Progressive assembly with assembly stations located

around carousel

3. Work-in-process

WIP applications in electronics industry are common

4. Unique applications

Example: time testing of electrical products

mm 323 man sys 2014 fall 1 introduction material handling systems.pdf

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