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19 Οκτ 2013 (πριν από 3 χρόνια και 11 μήνες)

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Chapter 6

Process Selection

and


Facility Layout

1

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UCO

Forecasting

Product and

Service Design

Technological

Change

Capacity

Planning

Process

Selection

Facilities and

Equipment

Facility Layout

Work

Design

Process Selection
as Part of
System Design


Deciding on the way

the
production of goods or

s
ervices will be organized


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UCO

Process Choice Decisions

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Three Types of Goods and Services


Custom
,

or
make
-
to
-
order, goods and services


are generally produced and delivered as one
-
of
-
a
-
kind or in small quantities, and
are designed to meet specific customers’ specifications.


Examples:

ships, weddings, certain jewelry, estate plans, buildings, and surgery.


Option,

or
assemble
-
to
-
order, goods and services


are configurations of standard parts, subassemblies, or services that can be
selected by customers from a limited set.

Examples:

desktop
computers, Subway sandwiches,
vacation in tour,
BBA


Standard
, or
make
-
to
-
stock, goods and services


are made according to a fixed design, and the customer has no options from which
to choose.

Examples:

appliances, shoes, sporting goods, credit cards, on
-
line Web
-
based
courses, and bus service.

The Big Picture

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UCO

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Types
of

Goods
and Services



Custom

make
-
to
-
order




Option

assemble
-
to
-
order



Standard

make
-
to
-
stock

Types
of

Processes


1. Projects


2. Job
-
Shop


3. Batch



4. Repetitive/

(Assembly Lines)



5. Continuous

Types
of

Layout


1. Fixed Position Layout


2. Process/Functional Layout









3. Product Layout

Job
shop:

Small scale production

Batch:

Moderate volume production

Repetitive/assembly
line:

High
volumes of standardized goods or services

Continuous:

Very
high volumes of non
-
discrete goods

Types of Processes

Job
-
Shop

(intermittent process
)

Process/Functional Layout

Repetitive

(assembly line
)

Product Layout

Continuum

Make to Order

High
variety, low volume

Low utilization (5%
-

25%)

General
-
purpose equipment

Make to Stock

Low
variety, high volume

High utilization (70%
-

95%)

Specialized equipment

Batch

Continuous


Product Layout




Flexible
equipment

Projects

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Batch

Repetitive

Volume, Variety and Process Matrix

Different Attributes
only

(Low Variety)


(such as grade, quality, size,
thickness, etc.)

Long runs only


Process/Functional
focus
(Intermittent)

projects, job shop

(machine, print, carpentry)

Kinko’s

Repetitive

(autos, motorcycles)

Honda


Product focus

(steel, glass)

Nucor Steel

Different Products:

(High Variety)


One
or few units per run,
high variety

(allows customization)


Different Modules

Modest runs,

standardized
modules

Mass Customization

(difficult to achieve,
but huge rewards)

Dell Computer Co.

Poor
strategy


Low
-
Volume

Repetitive Process

High
-
Volume

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(Batch)

0.1 min

0.7 min

1.0 min

0.5 min

0.2 min

Assembly
-
Line
Balancing

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Assembly
-
Line Balancing

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UCO

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Assembly
-
Line Balancing


An
assembly line

is

a product layout dedicated to combining the
components of a good or service that has been created previously.


Assembly line balancing

is a technique for grouping tasks to balance the
workload on workstations.


Cycle time (CT)

is the interval between successive outputs.





Min. number of WS needed = Sum of task times/Cycle time =


t / CT




Individual WS efficiency = t / CT




Assembly Line Efficiency =


t / (N*CT)


0.1 min

0.7 min

1.0 min

0.5 min

0.2 min


5 workstations: CT = 1 minute; 1 assembly every 1 minute.


3 workstations: CT = 1 minute; 1 assembly every 1 minute.


1 workstation: CT = 2.5 minutes; 1 assembly every 2.5 minutes.








Maximum Allowed Cycle Time:


MACT
= A / R

where

A = Available time to produce the output
(Hrs/day or Min/day)


R = Required output Rate (units/day)




(be careful with time units)


Example: [8hrs/day] / [160units/day] = 0.05 hrs/unit or 3 minutes



Assembly
-
Line Balancing

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0.1 min

0.7 min

1.0 min

0.5 min

0.2 min

Funnel Analogy of
Bottlenecks

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Little’s Law

J.D.
Little (1961) developed a simple formula that explains the
relationship between flow time (T), throughput (R) and work
-
in
-
process
(WIP), which is known as Little’s Law.


WORK
-
IN
-
PROCESS (WIP) = THROUGHPUT (R) * FLOW TIME (T)


Assume: Throughput

= 30 units/hr



Flow time

= 20 minutes or 1/3 hr



Therefore

WIP

=
30 units/hr x 1/3 hr = 10
units




Consider a voting facility that processes an average of 50 people per
hour and that on average, it takes 10 minutes for each person to
complete the voting process.



WIP = R*T



WIP = 50 voters/hr*(10 minutes/60 minutes per hour)



WIP = 8.33 voters



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Solved Problem

An accounts receivable manager processes 200 bills per day with an
average processing time of 5 working days.

What is the average number of bills in her office?

What if she reduces the time from 5 to 1 day using better technology?


Solution
:



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Automation
: Machinery that has sensing and control devices that
enables it to
operate with minimal input from an operator.


Fixed automation


Programmable
automation



Automation


Machine technology


NCM for drilling, cutting, etc


Automatic identification systems (AIS)


Bar codes, toll pass


Process control


Glass temperature


QA charts


Vision system
-

Replacing human inspection: level in medicine bottles


Robot


Imitation of human arm for boring and dangerous jobs


Automated storage and retrieval systems (ASRS)


Automated Guided Vehicles (AGV)


Flexible manufacturing systems (FMS)


One computer system
controlling several machines and material handling


Computer
-
integrated manufacturing (CIM)


One computer system
spanning over engineering, inventory, manufacturing, warehousing
and shipping

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Layout
: the configuration of departments, work centers, and equipment,
with particular emphasis on movement of work (customers or materials)
through the system


Process/Functional layout


Product layout


Combination layout


Fixed
-
Position layout (Projects)


Facilities Layout

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Gear

cutting

Mill

Drill

Lathes

Grind

Heat

treat

Assembly

111

333

222

444

222

111

444

111

333

1111

2222

222

3333

111

444

111

Process/Functional
Layout

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Process/Functional Layout

A
process/functional
layout

consists of a functional grouping of
equipment or activities that do similar work.

Examples
: offices, hospitals.

Advantages

of product layouts include a lower investment in general
purpose equipment, flexibility, and the diversity of jobs inherent in a
process layout can lead to increased worker satisfaction.

Saba Bahouth


UCO

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Product Layout

A
product layout

is an arrangement based on the sequence of operations
that are performed during the manufacturing or service.

Examples
: Subway sandwich shops, automobile assembly lines.

Advantages

of product layouts include lower work
-
in
-
process inventories,
shorter processing times, less material handling, requires lower labor skills,
and simple planning and control systems.

Gear

cutting

Mill

Drill

Lathes

Grind

Heat

treat

Assembly

111

333

222

444

222

111

444

111

333

1111

2222

222

3333

111

444

111

Process/Functional
Layout


Cellular Production


Group Technology

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UCO

-
1111

-
1111


222222222

-

2222

Assembly


3333333333

-

3333

44444444444444

-

4444

Lathe

Lathe

Mill

Mill

Mill

Mill

Drill

Drill

Drill

Heat

treat

Heat

treat

Heat

treat

Gear


cut

Gear


cut

Grind

Grind

Cellular Manufacturing Layout

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Group Technology

/
Cellular Layout

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Drill

Polish

Work Cell

Forming a Cell

A U
-
Shaped Production Line

1

2

3

4

5

6

7

8

9

10

In

Out

Workers

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Advantages


Can
handle a variety of
processing requirements


Not particularly vulnerable
to equipment failures


Equipment used is less
costly


Possible to use individual
incentive plans

Process/Functional
Layouts

Disadvantages


In
-
process inventory costs
can be high


Challenging routing and
scheduling


Equipment utilization rates
are low


Material handling slow and
inefficient


Complexities often reduce
span of supervision


Special attention for each
product or customer


Accounting and purchasing
are more involved

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UCO

Advantages


High
rate of output


Low unit cost


Labor specialization


Low material handling cost


High utilization of
labor/equipment


Established routing and scheduling


Easy
accounting and purchasing


Product
Layout

Disadvantages


Creates dull, repetitive jobs


Poorly skilled workers may neglect
maintenance and quality


Fairly inflexible to changes in volume


Highly susceptible to shutdowns


Needs preventive maintenance


Individual incentive plans are
impractical

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Warehouse and storage layouts


Retail layouts


Office layouts


Service layouts must
be functional and
aesthetically
pleasing

Service Layouts

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UCO