Lecture 2 - Why Study the Design Process [Compatibility Mode]
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Transcript of 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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measuring the design process cost
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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measuring the design process cost
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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measuring the design process quality
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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measuring the design process quality
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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measuring the design process time
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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measuring the design process time
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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history of the design process concurrent engineering
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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history of the design process concurrent engineering
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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history of the design process concurrent engineering
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?