Perhaps you have a SawStop table saw or have seen a demo. With SawStop, the blade stops instantly on encountering human flesh. I recall seeing a demo at NIWeek 2005, in which National Instruments used its FPGA-based industrial programmable automation controller to implement the SawStop algorithm. In the NI demo, a Compact RIO system induces a 200-kHz sine wave on the saw blade through a known impedance and monitors the sine-wave amplitude at the blade. Human contact greatly increases the capacitance of the blade, thereby decreasing the sine-wave amplitude and triggering a brake to stop the blade. NI enhanced its demo with a PXI Express-based image-capture system that showed the saw in action. In the NIWeek demo I saw, a hot dog stood in for a human finger. (You can still view a video of the demo at www.ni.com.) The SawStop website, though, has a gallery of fingers saved by the technology.
It’s a nice system, but of course it’s not free. In a Sept. 29 Washington Post column titled “Saving the world from saws—one finger at a time,” Kathleen Parker questions whether the Consumer Product Safety Commission should mandate a SawStop-like feature on all table saws. The feature adds about $100 to the cost of a saw right now, she reports, but would prevent about 3,500 digits from being lopped off each year.
Parker acknowledges that she hasn’t lost much sleep over table-saw safety. (She doesn’t mention whether she dabbles in carpentry when not writing columns for the Post.) But she does see the proposed mandate of the safety feature as “…a microcosm of the fundamental conflict that undergirds most political division in this country. Should we let the free market handle the problem? Or should government intervene to fix it?”
Conservatives, she writes, would protect people’s right to be careless and lop off their fingers while saving $100. And of course, lifetime costs of a saw equipped with the technology could be even higher for careless people or ones who want to repeat the hot-dog experiment. SawStop reports that activation of the brake generally destroys the saw blade (it may be worth repairing expensive blades) and requires a new brake cartridge that costs from $69 to $89.
The power-tool industry takes this conservative position. According to a June 9 article in Bloomberg Businessweek, “The Power Tool Institute, a Cleveland-based trade group of major manufacturers including Robert Bosch, Stanley Black & Decker (SWK), Ryobi, and Techtronic Industries, is fighting [SawStop founder] Gass’s efforts [to mandate the technology]. They say requiring a blade brake would destroy the market for the cheapest, most popular saws, adding $100 or more to the price of consumer models that typically sell for less than $200. The CPSC puts the industry’s cost at about $70 million a year.”
Liberals, on the other hand, would of course require that the safety feature be included on all table saws, as would SawStop founder Stephen Gass. Writes Parker, “After all, isn’t the cost to society from injured workers unable to make a living far greater than a few extra bucks added to the price of a tool?” In fact, the National Consumers League puts the cost of treating table-saw accident victims at more than $2 billion per year, so a cost-benefit analysis would seem to favor requiring the safety feature.
Parker, generally a conservative, nevertheless comes down on this side: “Clearly, the answer is to install the braking technology on all saws and figure out how to reduce the cost.”
I like that solution—it turns a political problem into an engineering one, and she doesn’t doubt that engineers are up to the task of solving the problem.
Rick Nelson
Executive Editor
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