Lecture 2 - Why Study the Design Process [Compatibility Mode]

7/23/2019 Lecture 2 - Why Study the Design Process [Compatibility Mode]

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Why Study the Design Process?

Lecture 2

Tuesday, Sept. 8, 2015


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why study the design process?

have been designing products for a long time (simpleto complex)

each product is result of design process

techniques to ensure good results

why study the process? continuous need for new, cost-effective, high quality products

complex products

global marketplace must develop new products faster must be efficient

85% of problems with new products are result of a poor designprocess


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measuring the design process

3 measures of effectiveness of design process cost

quality

time

regardless of product, customer and managementwant it:

cheaper

better faster


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measuring the design process cost

actual cost of design is small part of manufacturingcost

e.g. only 5% of manufacturing cost is for design activities to develop

it

Figure 1.1


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cost of product committed early in design process e.g. 75% of manufacturing cost committed by end of conceptual

design phase

actual cost incurred is quite low


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effects of quality on cost of manufacturing much greater than 5%

e.g. coffee makers

manufacturing efficiency and design quality have sameinfluence

results of design process can change manufacturing cost by50%

cost of design cheap, but design greatly affects cost:

the decisions made during the design process have

a great effect on the cost of a product but costvery little


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measuring the design process quality

quality affected by results of design process

quality cannot be built into a product unless it isdesigned into i t

what determines quality? composite of factors

responsibility of design engineer

decisions made during design process determine quality as

perceived by customers: works as it should

lasts a long time

is easy to maintain

looks attractive

incorporates latest technology has many features


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Xerox study indicator of quality: line fallout measure of number of components that do not fit together during

assembly

assumes: quality control used

components reach assembly within specifications

then, components that dont fit are poorly designed

must be scrapped or reworked

adds cost


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results of Xerox study:


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measuring the design process time

time to produce a new product isaffected by the design process

e.g. number of design changes made by 2auto companies with different designphilosophies

iteration is essential, but late changes aremore expensive

a change costing $1000 in engineering timeearly in design process may:

cost $10,000 during product refinement

cost $1,000,000 or more after

production started


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B was still making changes afterrelease for production

still designing while selling

tooling and assembly line changes, recalls

costly A made many changes early in the

process design finished before production

more engineering time and effort required

A made more changes than B more design alternatives explored

A took less time than B


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differences due to differences indesign philosophies:

A: assigns large staff early

encourages use of latest design techniques encourages exploration of all options early

B: assigns small staff

pressured for quick results

discourages exploration of options

curves represent design philosophiesof early 1980s of:

A Japanese company

3 years from problem to production

B American company 5 years from problem to production


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history of the design process

during design ideas developed into hardware usable as product

product is result of process that combines:

people and their knowledge tools

skills

requires time and money

if they are good, skilled, work in well-structured environment

can do the design efficiently

design a quality product

design process is:

the organization and management of people and the informationthey develop in the evolution of a product


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history of the design process

earlier times: one person could design and manufacture entire product

one person had sufficient knowledge to manage all aspect of design

and construction of even large products ships, bridges

middle of 20th century: products, manufacturing processes more complex

one person cant understand it all

different groups became responsible for

design

manufacturing

marketing

overall management this led to over-the-wall design process


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history of the design process over-the-wall

engineering design process walled off

marketing people communicate need to engineering one-way communication information thrown over the wall

engineering interprets requests, develops concepts, refines intomanufacturing specs thrown to manufacturing

manufacturing interprets info and builds what it thinks engineeringwanted

but: often what is manufactured is not what customer had in mind


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history of the design process over-the-wall

problem due to weaknesses in this developmentprocess

marketing cant communicate to engineering clear picture

no contact between designers and customers, limited withmarketing

poor understanding of design problem

designers not experts in manufacturing

parts may not be able to be made

required equipment may not be available

this over-the-wall approach is: inefficient

costly

results in poor quality some companies still do this


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history of the design process concurrent engineering

late 70s/early 80s: concept of simultaneous engineering developed

began to break down the walls

emphasized simultaneous development of manufacturing processand product development

1980s: simultaneous engineering philosophy broadened:

concurrent engineering


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concurrent engineering 9 key features: focus on entire product life

use and support design teams

processes as important as products attention to planning for information-centered tasks

careful product requirements development

multiple concept generation/evaluation

designing in quality during every phase

concurrent development of product and manufacturing process

emphasis of communication of right information to the right peopleat the right time


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looks different than over-the-wall method

primary focus is on integration of: teams of people (stakeholders)

design tools and techniques information about product and processes used to develop and manufacture it


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teams: eliminates many problems with over-the-wall method

different people involved at different stages of development

information: key point is concern for information must be shared

not only development but distribution

not only drawings but requirements, concepts, process plans

tools/techniques connects teams with information

important aspect of concurrent engineering is concern for both: product development

process development

product development process

manufacturing processes


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the life of a product

designers involved in product development shouldunderstand subsequent phases of a products life


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design problems

typically question: What size SAE grade 5 bolt should be used to fasten together two

pieces of 1045 sheet steel, each 4 mm thick and 6 cm wide, whichare lapped over each other and loaded with 100 N?

need is clear, know methods of analysis, easily understood no necessity to design joint solution already given (grade 5 bolt),only determine diameter

straight from textbook formulas plug and chug

slightly different problem:

Design a joint to fasten together two pieces of 1045 sheet steel,each 4 mm thick and 6 cm wide, which are lapped over each otherand loaded with 100 N.


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design problems

only apparent difference is opening clauses

2nd might be easier to understand? dont need to know how to design against shear failure in bolts

more latitude in generating concepts

but, which is best?

depends on other factors

not as well defined as 1st

more information required, questions to be answered


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design problems

1st problem: analysis find correct formula and plug and chug

only one correct answer

2nd problem: design ill-defined, all information not given

potential solutions not given, constraints incomplete

must fill in missing information

no correct answer

may be good solutions, but what is best solution?

for mechanical design:

must also create a piece of working hardware a product

mechanical design problems begin with an ill-defined need andresult in a piece of machinery that behaves in a certain way thatmeets a perceived need


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design problems

problem solving

regardless of what problem is being solved, sevenbasic actions are taken:

establish need plan how

understand the problem

generate solutions

evaluate alternatives

decide on solutions

communicate the results

not in 1-2-3 order intermingled and iterative


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design problems

types of design problems selection design

configuration design

parametric design original design

redesign

most problems are a mix of these various types


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knowledge and learning during design

as knowledge is gained, design freedom is lost

at beginning great freedom few decisions made, little capital invested

in production limited freedom changes expensive


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questions?

Lecture 2 - Why Study the Design Process [Compatibility Mode]

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