Here are two good designs in the house. Used them frequently as good example for my students. First, my daughter's first iPod, now no longer functioning and needs battery change, and an ice tray.
Where are the good design aspect on this nice iPod, beside the styling & functionalities?. Well, they're the little grey spot at the center of the holder and the holder itself. Why?. The grey spot is made of silicone rubber. Without it the iPod just drop-off the holder to the floor...bang!..
Why again?. One of the reason people using rubber is because of they increases friction, things dont slip easily, think of your car tyres , underneath your desk foot or under yours!. Other function is fluid-gas tight sealing, that bring us to birth control or health issue, but its completely off topic here :).
Now it's the holder turn, it has to be engineered correctly to push the iPod against this rubber spot. Not to firm so its too difficult to put in the iPod, and also not to weak so the iPod stays put in it.
How does it works?. The friction works if we put a force perpendicular to the friction surface. So we know now why the holder has 'wings', they're there to generate clamping force against the grey spot.
This design aspect requires deep tought in ideas, design, engineering and manufacturing. Only a talented designer will came with this. Oh yes, I can imagine how the 'American' engineers going very tough and uncompromising against Chinese Manufacturer on plastic materials and holder dimensions ;). My hat's off to the designers!.
The humble ice tray.
The second example is my 10 years old 'Korean Made' refrigerator Ice Tray. The trays repels ice cubes by twisting the tray handle, so a shearing deformation occurs between the ice and the smooth plastic wall container..then the cubes fall.
Very clever, just what we have to do to get ice cubes out back in the 80's. Take the tray out, put under running water and bangs and twist the tray :) to get the ice.. in short, making some noises.
Also heavy engineering must be involved here, and prototyping for sure to check whether the design works. Plastic material used must be of high quality..there must be no too critical area on the stressed tray...here are some numbers.
10 years x 365 days x 2x twists = 7.300 times and still going (I bet the manufacturer aims for at least 100.000 twist action..). Now add same amount of stresses in the container, because water expands little bit when frozen, also add temperature change from 25deg C to 0 deg C repeatedly. Whew!..that's a lot to be considered. Even the collector tray below has cracked its bottom, the test of time is unforgiving. That's what it takes for a good design, reliable functioning.