Flexible Manufacturing System

(Strategy) (FMS)

Conceptual idea is attributed to David Williamson

in the 1960’s, but it took development of CNC and
programmable controllers to make the concept
truly viable.

Topics

w Current world & business environment

w Manufacturing system basics
w Types of flexibility
w Flexible manufacturing system (FMS)
w Flexible manufacturing cell (FMC)
w System trade-offs

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What's Happening Today?

w Capital costs are increasing
n Change
w Multi-national marketplace
n Change
w Value of $$ is changing
n Change
w Incredible market dynamics
n Change
w "Virtual" technology explosion
n Change
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 Manufacturing Systems

w Definition
w Manufacturing system components
w Computer control system functions
w Human resources
w Classification of manufacturing systems

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Definition:
Manufacturing System

A manufacturing system is a collection of integrated

equipment and human resources, whose function is to
perform one or more processing and/or assembly
operations on a starting raw material, part, or set of
parts.

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Manufacturing System
Components
w What are they?
w How are they combined?
w How are they organized?
w Production machines
w Material handling system
w Computer control system
w Human resources

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 Classification of Manufacturing
Systems
w Types of operations
w Number of workstations & layout
w Level of automation
w Part or product variety (how to handle; types
of flexibility)

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Types of Manufacturing Systems

w Mass production (transfer line)

w Special systems
w Flexible manufacturing system (FMS)
w Flexible manufacturing cell (FMC)
w Stand-alone CNC systems

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Why FMS??

High Quality
w Increased
Productivity Lower Cost
w Cost-effective
Investment Shorter Lead Time

w Flexibility Respond to Change

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 FMS is Business Driven
w Improved profitability
n Reduced lead times
n Reduced inventory levels
n Rapid response to market changes
n Lower staffing levels
w Improved manufacturing effectiveness
n Increased operational flexibility
n Increased predictability
n Increased control

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FMS: Impact on Manufacturing

w Need for managing change
w More complex products
w Need for greater flexibility
w Need for faster time-to-market

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Definition: FMS

Group of machines or processes, integrated with

material handling equipment, and under the
direction of a (central) control system, to produce a
variety of parts, at non-uniform production rates,
batch sizes & quantities.

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 Part Design Flexibility vs.
Operating Flexibility
Part Design Flexibility

Operating Flexibility

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Types of FMS Flexibility*

w Product design — Makes it possible to
accommodate a variety of product designs,
including new products and modified designs;
stems from recent advances in manufacturing
controls that allow design details to reside in a
machine software rather than the mechanics of its
physical structure

* Fischer, G.W., "Computer Software for Flexible Manufacturing Systems,"

Handbook of Flexible Manufacturing Systems, Academic Press, Inc., 1991, pp.61-87

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Types of FMS Flexibility

(cont'd)
w Operating — Makes it possible to reduce
manufacturing costs while responding to changes in
manufacturing conditions, such as production
schedules and model mix; characterized by capability
to make up lost production (achieved in past through
large WIP inventory)
w System — Makes it possible to add or change
existing manufacturing processes to increase
productivity. Rembold et al. 1993

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 FMS: Important Technologies
w Microprocessor
w Digital system simulation
w Design optimization tools
w Computer aided process planning
w Process controlled quality
w More software control
w Advanced industrial controls
w Industrial robots

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FMS: Other Significant

Technologies
w Advanced sensors
w Improved diagnosis
w Higher speed
w On-line/in-process inspection
w Quick-change tooling
w Tool wear monitor
w Development with other processes, e.g., forming;
heat treat; assembly

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Invest or Not Invest??

w Type of equipment available vs. operations
needed
w Types of parts & number of part #'s
w Part tolerances & material requirements
w Design change expected
w Operational/schedule change expected

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 Invest or Not Invest?? (cont'd)
w Production volumes
w Product life & lead time requirements
w Direct labor available
w Dollars available to invest
w Other investment alternatives for company

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Part Manufacturing Target

for FMS
w Mid-volume
w Mid-variety

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Production Volume vs. Product

Flexibility
Transfer
Production Volume (parts/yr)

Line

Computer
Integrated
Manufacturing
System (CIMS)

Stand-alone
CNC

Product Flexibility (no. of part nos.)

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 System Trade-offs
w Transfer lines
n Large volume production/high output rate (~

15,000+ parts/yr)
n Parts are virtually identical; sometimes only one

part
n Changeover difficult/requires shutdown of line

& machine retooling

n Need to replace machines for major design

changes
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Transfer Line

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System Trade-offs (cont'd)

w Stand-alone CNC
n Efficiently accommodates part design change

n Reprogram for design changeover/design change

n Low production quantities (~up to 800 parts/yr)

w CIMS
n Between high production rates & high flexibility

(mid-volume)
n Fills in gap between transfer lines & low volume

CNC machines
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 Machining Center

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System Trade-offs (cont'd)

w Special system
n Least flexible CIMS
n Limited number of different parts (e.g., 2 -8) in same family
(volume: ~1500-15,000)
n Includes special purpose machine tools
n Lot sizes: 200 -10,000
n Similar to transfer line in flow
w Flexible manufacturing cell (FMC)
n Most flexible of CIMS, but lowest production rate (40-800
different parts @ 15-500/yr)
n Mixed CNC machine tools, maybe w/o automated m.h.
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System Trade-offs (cont'd)

w FMS
n Several part families, e.g., 4-100 different part #'s
with 40-2000/yr
n Lot sizes may vary between less than 50 to 500 or
more
n Central load/unload & palletized fixtures
n Routing varies with part loading & FMS type
n Typically central computer (monitor, schedule &
control)

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 FMS Concepts

w Single station routing part flow

w Sequential routing part flow
w Random routing part flow

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FMS Concepts
w Single station
n Tailor to design or operational change need
n Attributes of both random & sequential flow
n Problem areas: overall accuracy & required head
investment

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Single Station FMS

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 Head Changer

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FMS Concepts (cont'd)

w Sequential flow
n Accommodates operational part mix change;
higher throughput capacity
n Similar operation sequences
n Simpler material handling
n Potential problems: over & under utilization;
machines repeated for repeated operations

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Sequential FMS

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 Sequential FMS Examples

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FMS Concepts (cont'd)

w Random flow
n High degree of design flexibility & limited
operating flexibility
n Complex material handling system
n Potential problems: availability of machine tools;
reduced capacity with over & under utilized
machine tools

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Random FMS

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 Head Indexer

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John Deere Tractor

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FMS at John Deere

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 FMS: Machine Tool Trade-offs

Tooling Flexibility Prod. Rate

Head Changer multiple tool moderate moderate
Head Indexer multiple tool lowest highest
Machining Center single point highest lowest
(spindle)

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Computer Functions for FMS

w Control of each workstation
w Distribution of control instructions to workstations
w Production control
w Traffic control
w Shuttle control
w Workhandling system monitoring
w Tool control
w System performance monitoring & reporting
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Personnel Requirements
for FMS
w System manager
w Electrical technician
w Mechanical/hydraulic technician
w Tool setter
w Fixture setup & lead man
w Load/unload man
w Rover operator
w Other: NC programmer; computer programmers;
other support staff
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 Benefits to Business Elements
w Manufacturing
n Combine low part volumes to get economies of scale
n Single system manager benefits
n Adaptable to several product life cycles
n Simplified new product introduction on existing equipment
w Product Engineering (Design)
n Facilitates design update & refinement
n Encourages design innovation
n Facilitates use of existing designs for new applications

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Benefits to Business Elements

(cont'd)
w Marketing
n Lower cost basis for mid-volume production
n Shorter lead times/adapt to market dynamics
n Expand capacity to growth needs
n Respond to schedule/model mix
w Finance
n Better use of capital investment dollars
n Better tailor capacity & volume
n Produce old & new designs on the same production
equipment
n Lower new product introduction cost
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Manufacturing Cells

w Single station manned cells

w Single station automated cells
w Applications of single station cells
w Analysis of single station cells

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 Single Station Manned Cells

w Requires shortest amount of time to

implement
w Requires least capital investment
w Technologically, easiest to install & operate
w Often results in lowest cost per unit produced
w Most flexible manufacturing system

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Single Station Automated Cells

w Reduced labor requirement/cost

w Easiest & least expensive among automated
systems to implement
w Higher production rates possible
w First step in implementing integrated multi-
station automated system

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Applications of
Single Station Cells
w CNC machining center with parts carousel & automatic
pallet changer
w CNC turning center with parts storage tray & robot (same or
different parts)
w Cluster of CNC turning centers, each producing different
part
w Plastic injection molding machine with mechanical arm to
remove part
w Automated electronic assembly machine
w Robotic assembly cell
w Stamping press that punches & forms small sheet metal
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 Analysis of Single Station Cells

w Determine number of required workstations

n Include setup time
n Consider availability & machine utilization
n Consider worker efficiency
n Consider defect rate
w Determine number of machines for single
worker (cluster of machines)

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System Trade-offs

w Advantages vs. disadvantages

w Pluses vs. minuses
w Pluses vs. other pluses
w Cost vs. benefits
w Optimization strategies

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