environmentally conscious design & manufacturing class...

esign & Manufacturing

scious uring

do with it?

rland

Environmentally Conscious DDate: 5/1/00 1

Environmentally ConDesign & Manufact

Class 23:What does Quality have to

Prof. John W. Suthe


quality have to dos design and

hat we wish to tie

ap prevention

ironmental


Objective

Like the question asks: “what does with environmentally conscioumanufacturing?”

Three key quality-related concepts tto the environment....

• Quality improvement - waste/scr

• QFD & environmental design

• Taguchi’s loss function --- an envperspective


epts

acturing process

rom the processsurface finish,

etc.

rmanceures


Basic Quality Conc

• Consider block diagram for a manuf

• Performance measures (outputs) fmay include: Part dimensions, machine power, tool life, shrinkage,

ProcessPerfoMeas

ControllableInputs

UncontrolledInputs


ation

n

of variation thate system (systemgmt. responsible

x


Manufacturing Vari

When variables not controlled: variatio

Two types of manufacturing variation:• Common causes (Deming): sources

influence every product. Define thfaults). Chronic problems (Juran). M

µx

σx


n (cont.) of variation thatme of the parts.poradic problems the process.

time


Manufacturing Variatio• Special causes (Deming): sources

arise unpredictably - influence soAlso referred to as local faults. S(Juran). Often correctable locally at


ariation

Product

Use

Product Use

Noise


Product Performance V

Product

Design

Manufacture

& Assembly

Process

Nominal

Design

Variable

Levels

Actual

Variable

Values

Manufacturing &

Assembly Noise


ation (cont.)

ner Noise

Performance of Prod.at point in Future


Product Performance Vari Design-Mandated Target

Manufacturing Variation

Parts “as manufactured”

Outer Noise

Performance ObservedDuring Product Use

In


ging

e over time.


Effect of Wear and A

Process mean and variability chang


ce to engineering

x

per Spec

Scrap


Quality

Traditionally defined as conformanspecifications.

µx

σxLower Spec

Nominal ValueUp


oes not promotet.

x

per Spec


Quality (cont.)

Traditional definition of quality dnotion of never-ending improvemen

Nominal Value UpLower Spec

BestUnacceptable

Good


loss function to:

the loss is oftenreferred to as“societal loss”


Loss Function

Taguchi advocates the use of a characterize quality. Quadratic form

L = k(x - m)2

Nominal Value

x

Loss


om varb., loss is“average” loss

e Loss Functionomotes conceptstaying onget and keepingriation small!!


Expected Loss

Since the characteristic X is a randalso a random varb. - characterizes

Loss

mx

µx

σx

Thprof tarva

E L X( )[ ] k µx m–( )2 σx2

+=


er. Reliability is a last over time.

Use

time


Reliability

Would like a component to last forevmeasure of a component’s ability to

Component

failure distribution


)

an of the failurecomponent

can weease MTTF?

ved MTTF’

nent

er Approach


Example (cont.

• MTTF (mean time till failure) - medistribution - expected life time of a

Component MTTF Howincr

ComponentMTTF’

Component

ImproCompo

orTraditional Approach Bett


ntion

re improvementshrough design

ss control (SPC)riation and then

s and values forst -- make productriation, effects of


Issue 1: Scrap Preve

Fundamentally only two places whecan be made: within the process & t

• Process: employ statistical procemethods to identify sources of varemove them

• Product design: select design typethe design parameters that are robuless sensitive to manufacturing vaaging, and differences in usage.


rts

rocess - use this control charts

causes? Controls our attention &

XX

X


SPC - Control Cha

Samples are collected from the pdata to characterize process & make

SPC - Is process free of special charts tell us where we should foculook for improvements.

Process

X XX

XX X X

XX

X X X


UCL

LCL

x=

UCL

LCL

R-

rovement


SPCx-

R, R

ang

e

Control Imp"Out-of-Control"


erformancesponse

educed performancesponse variation


Robust Design

Adjust

Controlfactors Product

functioningin the field

Productfunctioningin the field

PreNoise

factors

Noisefactors

ControlFactors

Rre


eployment

e customer” intos throughout the

C3238


Issue 2:QFD: Quality Function D

• QFD (1980’s): Map the “voice of ththe product -- cascade the effectorganization.

A BProduct life 1 2Cost 3 4Performance 4 3Total 8 9

Feature Alternatives

PerformanceMetrics


ment

the environment

trics in QFD

C3232

10


QFD & the Environ

• One “voice” of growing importance:

• Need to consider environmental me

A BProduct life 1 2Cost 3 4Performance 4 3Environment 3 1Total 11 10

Feature Alternatives

PerformanceMetrics

NEWMetric


n View

t

o

xx

o

ge Data


Issue 3: Loss Functio

Mean - xVariance - o

x

xx

xx

x

o

oooo

o

Toner Cartrid


ing Product

mean

variance

Expected Loss


Loss Behavior - Deteriorat

0

20

40

60

80

100

0 3 6 9 12 15 18 21 24 27 30 33 36 39

time


ay Strategy

s

T2


Consider Use & Throw-aw

0 T1 T2

Product Replacement Point

0 T1

Loss (Cost)

Loss (Cost)


Function

uct replacementsl benefit.

nly considers theduct. We must

e consider thewould apply to


A Problem with the Loss

• Lengthening the time between proddoes not seem to produce a societa

• Problem is that the loss function onegative aspects of using a proconsider benefits as well.

• Previous graph suggests that wcumulative effect of loss (same benefits).


le

Product Disposal

MaterialDisposal


Product Life Cyc

NatureRaw Materials/Energy Acquisition

MaterialRefinement

Product Creation

Product Reuse

Remanufacturing

Recycling


omics

with our desire tonsible, i.e., that

t “take-back”, we products coming

hment / reuseing

he product value.


Environment & Econ

We need a metric that is consistent be more environmentally respoencourages longer use cycles.

Also, if we are seriously looking aneed to know the value of the usedback.

High value used products -- refurbisLower value used products -- recycl

The action to be taken depends on t


action

x

B(x)

L(x)

-L(x)


A New Metric: Satisf

Loss

Benefit

S(x)=B(x)


isfaction

t

e=T

EOL


Value

Value Definition: The cumulative satremaining in a product.

S(x)

T

Value at tim


at S(x) is

f products is

unctions of time,


Expected Value

From our previous work, we know th

The expected satisfaction for a set o

if the mean and variance are linear f

S x( ) S0 K x m–( )+2

=

E S X( )[ ] S0 K µx m–( )2 σx2

++=

µx µ0 k0t+=

σx2 σ0

2k1t+=


nt.)

is the cumulativet time t

en it reaches theent standpoint

up to time t


Expected Value (co

The value of a product at time, t, satisfaction still left in the product a

V(0) = the value of a new product

V(EOL) = the value of a product whend of its life -- useful from environm

CV(t) = V(0) - V(t) = Consumed value

V t( ) S t( ) td

t

T

∫=


g

0.05

An example:nominal value for a given product is 8.5.

Application of value concept shifts mfg. mean to 8.55, incr. quality & extending life of product.


Decision-makin

00.01

0.020.03

0.04

8.4

8.45

8.5

8.55

8.60

5

10

15

20

Mean in.

Val

ue in

dol

lars

($)

Value Function at T=0 MTTF=4 k0=-0.016 k1=0.000256

Standard deviation in.Mean in.

Val

ue (

$ x

10)

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