Friday, June 20, 2008

Synergy of design for disassembly and shock

One of the more popular refrains of the sustainable design movement is to "design for disassembly". The (correct) theory being that if a part is too difficult to take apart, and is made of more than one materials (like nearly all products are), it will not be recycled. I am a big proponent of designing for disassembly, but have recently come across a problem...shock.

Just think of all of the different products you use in your life that can experience shock (from dropping?) on a regular basis...



TV Remote
Any other remote control for that matter
Xbox controller
Cordless Phone
Hair Dryer
Calculator (I'm a nerd)
every children's toy ever made (it seems)
Cell phones

Whether dueit is unscrewing half a dozen screws on the small remote or trying to crack open the ultrasonic weld on your cell phone, the disassembly (and consequently recycling) of these products can be prohibitively labor intensive.

We are better than this. I am convinced that it is doable to concot some clever geometry (a variation on the good old snap latch) that enables a device to withstand necessary shock while remaining easily disassembled. It is not a tough balance to strike, it is just that we are used to seeing things fastened with a safety margin of roughly 2 gazillion. We can afford to bring that down.

My remote control has 6 screws keeping the two halves together. These screws assure that the plastic shell will crack from shock before it pops in half. However, it is overkill. This small device doesn't need 6 screws. Think critically, what kind of shock is a remote control going to encounter? It will encounter point forces along its body, but what is the likelihood of it striking in such a fashion that the two halves of the remote attempt to rotate about each other like the hands of a clock? Furthermore, even if this unlikely even happens, surely the forces can't be much greater than 20 lbs (an estimation, but I feel comfortable with it. Slap an accelerometer on your remote if you don't). The point I'm driving at is that with some cleverly designed snaps, a remote control could withstand the forces it encounters in its lifetime while still being able to be twisted apart in one motion at its end-of-life.

So what is the takeaway here? Fasteners and ultrasonic welding are a cop-out. Be clever.

1 comment:

Nick said...

Nice post, I too have come across the same thought process, but like so many other great and morally correct ideas, there is always the financial curtain that holds us back. Its crazy the amount of plastic that is thrown out on a daily basis, and as cool as a rubbery co-molded toothbrush may feel, its an environmental nightmare. Im all about a significant increase in bottle deposit fees and some type of green incentives as reverse psychology to fool the money grubbing juggernaut companies into making more recyclable friendly products. Makes me wonder sometimes how much money has stunted the evolution of mankind...