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.