Thursday, June 01, 2006

Table saw that turns off when it touches flesh

When I went to high school, one day someone in shop lost a finger in a table saw. Additionally, once when I was working on one of my own projects with a chop saw, I was moving so quickly that I almost severely damaged my hand. Technologies like this could have prevented both of those things.

A table saw has been invented that will detect when flesh touches the blade, turn off, brake the blade, and pull the blade out of the way of the incoming feed:

Making the Case for a Safer Table Saw

The video (located below the picture in QuickTime or Windows Media formats) really speaks for itself. The creator of the device feeds a piece of wood with a hot dog on top of it into the table saw, and he does it QUICKLY. At the INSTANT the hot dog touches the blade, the electrical characteristics of the blade change (like a touch lamp) and it stops, has a brake applied, and is pulled down into the table saw and out of the way of the feed. The hot dog is hardly nicked.

An interesting side note is that now that this device exists, people who previously thought they just had a lapse of safety judgment that led to their injuries are now seeking litigation against the table saw manufacturers for not taking advantage of technologies like this.

(this actually reminds me of the McDonald's coffee case; if a technology existed to make and store hot coffee without as much risk to someone's skin, would the woman who sued McDonald's receive more support from the public?)

Pretty interesting stuff.


Anonymous said...

HOW does it detect flesh as opposed to, say, soft foam, which I've had to cut b4?

Theo said...

Primarily due to things like the electrolyte in flesh (i.e., the water and all the gunk in it), the electrical characteristics of a piece of metal can change greatly when in contact with it.

However, in materials like foam and wood that act as insulators (dielectrics, actually), they have little impact on the actual characteristics of the metal itself.

Basically, you can test the metal's impedance (that's like it's resistance, but it includes storage effects, like capacitance and inductance) and that impedance will change when in contact with flesh (even a hot dog).

This is my impression of how it works. I haven't actually looked at how they explain how it works, but it seems like this would have to be the way it works.

Touch lamps have worked this way for years (there are a NUMBER of ways they detect whether they're being touched by a finger and not by, for example, a piece of foam).

So sure, certain materials you won't be able to cut with this saw. However, as long as you're cutting wood or foam or a large number of other dielectrics, you'll be fine.