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					             Design--a multiparameter problem

      Function

Does it work?
How reliably?

Over what conditions
does it work?

Practicality, ease of use
 i) the flashing 12:00 on a VCR
 ii) a recipe that calls for 25 ingredients
 iii) a remote-controlled garage door
Cost

       a) Market competitiveness
       b) Return on investment
                i) life of product
                           (software for DOS computers)
                ii) fragility of product
                           liquid vs. tablet medicine
       c) Manufacturability
                i) single or multiple steps in the process
                ii) multiple sub-assemblies
                iii) existence of machinery
                iv) expected market (quantity)
                           space shuttle toilet ~ 10
                           Pentium CPU ~ 10,000,000
       d) Transportability
                size, weight
Aesthetics

 a) visual appeal
 b) size, weight
         i) small and light is good:
                     camcorders, cell phones
         ii) big and heavy is good:
                     frypans, tools
         iii) illusion
                     thin frypans made to look thick
                     plastic car grills made to look like metal
Quality control

 a) Some failures OK
       screws without threads
       a mousetrap that doesn’t trip
       a floppy disk that won’t format

 b) Failures not OK
        space-suits
        pacemakers

 c) “Zero defects”?


            Electrodyne
            pacemaker, 1958
Life Expectancy

       a) single use
                cameras
                razors
                British Seagull motors

       b) outright failure
                TV picture tube

       c) designed to wear
               brake pads
               tires

       d) “Lifetime”
                artificial hip joint
Repair

 a)   Throwaway--plastic spoon, hand mixer
 b)   Fix vs. replace--appliances
 c)   Length of corporate responsibility--warranty, parts
 d)   Customer service
Safety

 a) safety factor
        i) percent over design
                  elevator cable

         ii) statistical
                    average loading per square foot
                    “100 year” events

 b) mode of failure
       i) catastrophic--without warning
       ii) indicator
                 steels that crack without failing
                 noise on worn automobile brakes
       iii) gradual
                 growling of an old hand mixer
Packaging

       a)   size
       b)   protection during transport
       c)   assembled vs. non-assembled
       d)   completeness--”batteries not included”
Environmental
       i) pollution during manufacture
       ii) pollution during operation
       iii) pollution during disposal
       iv) biodegradation




    Sheetrock: a
    biproduct of
    flue gas
    desulfurization
Other

        a) product certification--e.g., UL listing

        b) Versatility
                i) temperature, humidity, etc.
                ii) foreign use--electricity requirements
          Design:

It’s not a science; it’s an art.

				
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posted:2/22/2010
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