I have used this knife, I am an angel investor in Scott's company. The thing is legit amazing. He labored for years to bring this to market and it shows.
Hm usually ultrasonic cutting tools have small, disposable blades, which are tuned so that they vibrate right. Also they can produce an intense burning sensation in either the hand you're using (if you hold wrong / too tight) or in your off-hand (if you hit something hard, like a bone, which can pick up the vibrations).
I'm sure there's an ultrasonic transducer in there but I wonder how a 40w transducer (this is typical power for hand-held) can move such a giant blade around at 40khz. It does not seem physically plausible to me.
Hey there, Scott here. I'm driving the knife at actually only 10W. When in resonance, this produces a stroke amplitude of 10-20 microns (depending on the spot on the blade) which is large enough to have a measurable impact on the ease of cutting. 50% reduction in peak force for tomatoes (as measured quantitatively with a robot arm), and I've seen even higher in other foods.
At this power level, there's no heating of the blade like the small blade tools you're describing. And firmware in the handle adjusts the operating frequency continuously to stay in resonance.
This all works because the ultrasonics aren't moving the blade like a reciprocating saw -- that would indeed require huge power. They're sending longitudinal shockwaves through the blade itself that cause the metal to expand and contract. Check out minute 2:30 in the video here to see that motion in action: https://youtu.be/cXjbSVt9XNM
If any home users cut on glass, they'll be rewarded with an unpleasant screeching sound. I can't say that was by design, but it's not undeserved ;-)
The ultrasonic motion acts as an amplifier for physical sharpness. So, it's sharpest when it's got a geometrically great edge, but even as that edge dulls, it behaves sharper when on vs. off. This is reflected in BESS testing, and also in robotic cutting.
Moreover, a huge amount of the force required for cutting normal foods is actually a function of friction, not just bevel sharpness. So the reduced friction on the blade faces from ultrasonic motion remains just as effective even if the cutting edge is dull. In fact, commercial ultrasonic cutting machines don't use sharp blades at all!
It's a good idea, but it's probably cheaper and, from an ecological standpoint better (than e-waste) to sharpen knives; a top-quality professional electric knife sharpener will set you back $170 and last you a lifetime; which is a third of the cost of the Ultrasonic's knife. Cool idea though.
I don't get it. How is buying a "top-quality professional electric knife sharpener" more ecological than buying a knife with a bit of electronics in the handle? Both are used by one person in your proposal and I would think, that it needs more energy to build the sharpener.
One does not even need a top-quality professional electric knife sharpener to produce an edge for kitchen work. An inexpensive 1500 grit whetstone suffices.
good point, it's within their audible frequency which is between 40Hz to 60kHz (65kHz in some dogs); the knife is 40kHz, so it will drive them completely crazy.
@Scott How much faster will the cutting board (wood & plastic) degrade? Do you recommend one over the other for this knife? Will you be making one best suited for this knife?
gnabgib|5 months ago
gurgeous|5 months ago
xyzzy123|5 months ago
I'm sure there's an ultrasonic transducer in there but I wonder how a 40w transducer (this is typical power for hand-held) can move such a giant blade around at 40khz. It does not seem physically plausible to me.
sheimend|5 months ago
At this power level, there's no heating of the blade like the small blade tools you're describing. And firmware in the handle adjusts the operating frequency continuously to stay in resonance.
This all works because the ultrasonics aren't moving the blade like a reciprocating saw -- that would indeed require huge power. They're sending longitudinal shockwaves through the blade itself that cause the metal to expand and contract. Check out minute 2:30 in the video here to see that motion in action: https://youtu.be/cXjbSVt9XNM
jerlam|5 months ago
sheimend|5 months ago
The ultrasonic motion acts as an amplifier for physical sharpness. So, it's sharpest when it's got a geometrically great edge, but even as that edge dulls, it behaves sharper when on vs. off. This is reflected in BESS testing, and also in robotic cutting.
Moreover, a huge amount of the force required for cutting normal foods is actually a function of friction, not just bevel sharpness. So the reduced friction on the blade faces from ultrasonic motion remains just as effective even if the cutting edge is dull. In fact, commercial ultrasonic cutting machines don't use sharp blades at all!
natas|5 months ago
ahofmann|5 months ago
AgentElement|5 months ago
samuli|5 months ago
unknown|5 months ago
[deleted]
balibones|5 months ago
tandr|5 months ago
natas|5 months ago
fuzzythinker|5 months ago
reassess_blind|5 months ago