FORMULATING A DESIGN PROBLEM

PART 2

Pengumuman – dari Puan Marina

• Sila download lab module untuk minggu depan dari portal lab project management

• Hantar drawing in template (assignment minggu lepas) next week by lab session. (except student baru). Individual. 1 day late submission -50%.

• In the detail drawing:• 1. title block• 2. top, front, left, iso view(3rd angle projection)• 3. dimensions

Recap

• Objectives the desired attributes of a design.

• Constraints strict limits that a design must meet to be acceptable.

Objective Tree

• A graphical representation of the objectives for the product.

• The top-level objectives in an objective tree, which is presented as a node at the peak of the tree, is decomposed or broken down into sub-objectives that are at differing levels of importance or that include progressively more details, so that the tree reflects an hierarchical structure as it expands downward.

• Ordered lists of the desired attributes of a design.• Sub-objective tells how to realize the top objective

Safe ladder objectives 1. The ladder should be safe

1.1 The ladder should be stable1.1.1 Stable on floors and smooth surfaces1.1.2 Stable on relatively level ground

1.2 The ladder should be reasonably stiff 2. The ladder should be marketable

2.1 The ladder should be useful 2.1.1 The ladder should be useful indoors

2.1.1.1 Useful to do electrical work2.1.1.2 Useful to do maintenance work

2.1.2 The ladder should be useful outdoors2.1.3 The ladder should be of the right weight

2.2 The ladder should be relatively inexpensive2.3 The ladder should be portable

2.3.1 The ladder should be light in weight2.3.2 The ladder should be small when ready for transport

2.4 The ladder should be durable

electrical

maintenance

small, transportable

light in weight

of right weight

outdoors

indoors

on level ground

on floors

inexpensive

portable

durable

useful

stiff

stable

Safe

SAFE LADDER

Marketable

Objective Tree for Safe Ladder

electrical

maintenance

small, transportable

light in weight

of right weight

outdoors

indoors

on level ground

on floors

inexpensive

portable

durable

useful

stiff

stable

Safe

SAFE LADDER

Marketable

electrical

maintenance

small, transportable

light in weight

of right weight

outdoors

indoors

on level ground

on floors

inexpensive

portable

durable

useful

stiff

stable

Safe

SAFE LADDER

Marketable

Pairwise Comparison Chart

• Helps to understand the relative importance of the objectives comparing objectives.

• To identify the values of objectives or their importance relative to one another and to order them accordingly.

• Procedure:1. compare every objectives with each of the remaining objectives individually2. add cumulative or total scores for each one of the objectives.

Objectives Cost Portability Usefulness Durability Score

Cost - 0 0 1 1

Portability 1 - 1 1 3

Usefulness 1 0 - 1 2

Durability 0 0 0 - 0

• 4 objectives are compared.• The entries in each box of the chart are determined as

binary choices, i.e. every entry is either a 1 or a 0. • The PCC for the ladder design shows that the objectives

ranked in the order of decreasing value or importance is:portability usefulness cost durability

A pairwise comparison chart (PCC) for a ladder design

Quality Function Deployment

• What is quality? 1. (Time magazine (1989))i. Works as it should ii. Lasts a long timeiii. Easy to maintain

2. Garvin (1987)i. Performanceii. Features iii. Reliability iv. Durability v. Serviceability vi. Conformance to conventions/

standardsvii. Aesthetics viii.Perceived quality/ reputation

of manufacturer

• A quality product:i. made of quality parts, which

are made by high-quality processes

ii. Functions or performs as expected (reliable)

iii. Lasts a long time (durable)iv. Easy to maintain

(serviceable)

Quality Function Deployment (QFD)

• A technique for identifying customer requirements and matching them with engineering design and performance parameters.

• Comes from a Japanese phrase “ … the strategic arrangement (deployment) throughout all aspects of a product (functions) of appropriate characteristics (qualities) according to customer demands.”

• Useful tool for formulating design problems for products in situations where several competing products are already on the market.

• QFD Table a chart that explicitly depicts the key relationships between customer requirements, engineering (or product) requirements, and the characteristics of competing products.

• General arrangement (5 regions):1. Customer requirements2. Engineering requirements3. Matrix of requirements relations4. Competitive benchmarks5. Engineering targets

Refer to notes on customer requirement

Quantifiable aspects of the system that can contribute to satisfying Customer Requirements.

Benchmarking -Comparing your design with that of competitors

Indicates the relationship between an engineering requirement and a customer requirement by an ‘x’ mark in the appropriate cell in the matrix.

Lists the units and the numerical values of the targets for each engineering requirement.

House of Quality-one variation of QFD

slid

es (

yes/

no)

fric

tion

fact

or

star

t sw

itch

forc

e (lb

f)

forc

e to

sha

rpen

(lb

f)

hold

forc

e re

quire

d (lb

f)

gras

p to

rque

(in

-lbf)

shav

ings

sto

reag

e (c

u.in

.)

no. s

teps

to e

mpt

y

120

VA

C (

yes/

no)

cord

leng

th (

ft)

poin

t con

e an

gle

(deg

rees

)

no. h

ands

to o

pera

te

wei

ght (

oz)

poin

t rou

ghne

ss (

mic

ro in

.)

Customer Requirements 1 2 3 4 5 6 7 8 9 10 11 12 13 14 CP A B

1 doesn't slide w hen using 0.10 9 3 3 3 9 1 3 3 0.92 needs little insertion force 0.05 9 9 0.83 requires little insertion torque 0.05 9 0.94 operates w hen pencil is inserted0.15 9 9 1.05 collects pencils shavings w ell 0.05 9 1 1.06 empties shavings easily 0.20 3 9 1 3 -3 0.67 plugs into w all socket easily 0.05 9 0.98 cord is long enough 0.05 9 0.89 grinds pencil to sharp point 0.20 9 3 0.7

10 needs only one hand tw o operate0.10 3 9 3 0.8

Total Importance 1.00

Performance current product(CP)

competitior A: Model #25 N 1 0 0 0 0 2 6 Y 6 20 1 20 6

competitor B

New Product Targets N 1 0 0 0 0 3 4 Y 6 18 1 18 5

Customer Satisfactio

n Rating (0.00 - 1.00)

Engineering Characteristics (units)

Im

po

rtan

ce w

t.

1 -311

-3

39

9

-9

9

31

-9

3

-3

11

House of Quality (for Product Planning)

• Room 1: Customer Requirements• Room 2: Customer Importance Weights• Room 3: Engineering Characteristics • Room 4: Correlation Ratings Matrix • Room 5: Benchmark Satisfaction Ratings• Room 6: Benchmark Performance• Room 7: New Product Targets• Room 8: Coupling Matrix

Exercise