You’re cutting yourself a single slice of cake. You grab a butter knife out of the drawer, hack off a moist wedge, and munch away to your mouth’s delight. The next day, you’re cutting forty slices of cake for the whole office. You grab a large chef’s knife, warm it with hot water, and cube out the sheet cake without causing too much trauma to the icing. Next week, you’re starting at your cousin’s bakery. You’re supposed to cut a few thousand slices of cake, week in, week out. You suspect your haggardly knifework won’t do.
In the home kitchen, any old knife will do the job when it comes to slicing cakes, pies, and pastries. When it comes to commercial kitchens, though, presentation is everything and perfection is the bare minimum. Thankfully, there’s a better grade of cutting tool out there—and it’s more high tech than you might think.
Shake It
Knives are very good at cutting food into distinct separate pieces. However, they have one major problem—food is sticky, and so are they. If you’ve ever cut through a cheesecake, you’ve seen this in action. Unless you’re very careful and deft with your slicing, the cake tends to grip the blade of the knife as it comes through. Try as you might, you’re almost always going to leave some marred edges unless you work very slowly.
While most home chefs and cafes can turn a blind eye to these sorts of things, that’s not the case in the processed food industry. For one thing, consumers expect each individually-packed morsel of food to be as cosmetically perfect as the last. For another, cutting processes have to be robust to work at speed. A human can compensate as they cut, freeing the blade from sticking and fettling the final product to hide their mistakes. Contrast that to a production line that slices ice cream bars from a sheet all day. All it takes is one stuck piece to completely mess up the production line and ruin the product.
This is where ultrasonic food processing comes in. Ultrasonic cutting blades exist for one primary reason—they enable the cutting of all kinds of different foods without sticking, squashing, or otherwise marring the food. These blades most commonly find themselves used in processed food production lines, where a bulk material must be cut into individual bars or slices for later preparation or packaging.
It’s quite something to watch these blades in action. Companies like Dukane and MeiShun have demo videos that show the uncanny ability of their products to slice through even the stickiest foods without issue. You can watch cheesecakes get evenly sectored into perfect triangular slices, or a soft brie cheese being sliced without any material being left on the blade. The technique works on drier materials too—it’s possible to cut perfectly nice slices of bread with less squishing and distortion using ultrasonic blades. Even complex cakes, like the vanilla slice, with layers of stiff pastry and smooth custard, can be cut into neat polygons with appropriate ultrasonic tooling.
The mechanism of action is well-understood. An ultrasonic cutting blade is formally known as a sonotrode, and is still sharpened to an edge to do its job. However, where it varies from a regular blade is that it does not use mere pressure to slice through the target material. Instead, transducers in the sonotrode vibrate it at an ultrasonic frequency—beyond the range of human hearing, typically from 20 kHz to 40 kHz. When the sonotrode comes into contact with the material, the high-frequency vibrations allow it to slice through the material without sticking to it. Since the entire blade is vibrating, it continues to not stick as it slides downwards, allowing for an exceptionally clean cut.
Generally, the ultrasonic sonotrode is paired with a motion platform to move the food precisely through the cutting process, and an actuator to perform the cutting action itself. However, there are also handheld ultrasonic knives that can be purchased for those looking to use the same technique manually.
Just don’t expect to get this hardware cheap. On Chinese industrial reseller websites, ultrasonic cutting rigs tend to start in the five-figure range, and go up from there. Prices can quickly increase for larger rigs, those with conveyors, or with more advanced capabilities. If you want a more specialized sonotrode or need to swap out different tooling for different target materials, expect to pay a suitable further sum for that capability, too. One saving grace, however, is that the sonotrode tooling doesn’t quite wear in the same way as a normal cutting blade, since it’s not solely relying on its sharpness to get a clean cut. These devices still need to be cleaned and maintained, but they don’t dull in the same way a simple knife does.
The technique isn’t solely applied to the food industry. The same techniques work for many other difficult-to-cut materials, like rubber. The technique can also be applied to various textiles or plastic materials, too. In some cases, the sonotrode can generate enough heat as it cuts through the materials to melt and seal the edges of the material it’s cutting through.
If you’re simply looking to cut some cake at home, this technique might be a little overly advanced for you. At the same time, there’s nothing stopping you from rigging up some transducers with a blade and a DIY CNC platform seeing what you can achieve. If you want the most perfectly cubed sheet cake at your next office party, this might just be the technology you’re looking for.
A step up from those vibrating knives used to carve the thanksgiving turkey.
We deployed this tech for production robotic dough scoring at Technology Brewing several times with great success. Before company pivoted into robotic mushroom harvesting.
Used ultrasonic blades to do reworks on electronic boards back in the day.
Loved how easy it was to cut QFP pins, split connector housings, etc.
Not the same model, but looked kinda like these guys: https://djausa.com/ultrasonic-cutting/
These knives seem to have some interesting properties, I wonder why they haven’t been used in surgery?
Surgical ultrasonic scalpels exist. They just arent as widely used as electrosurgical scalpels. Outside of orthopedics, the additional weight of the transducer is generally found to be more of a burden then the benefit of its end result, especially when compared with more advanced ESU systems like the Peak Plasmablade which uses a modulated waveform that drastically reduces thermal tissue damage common to older electrosurgical systems.
Whoa I was not ready for that soundtrack
This begs to be turned into some kind of cyberpunk vibro-sword, it already has a very nice chunky look to it
Good news: https://en.wikipedia.org/wiki/Metal_Gear_Rising%3A_Revengeance
Oh trust me, the soundtrack was already in my head
For some reason, I have 🎶I’m looking over, a four-loaf cleaver, that I overlooked before…🎶 in my head now.
Star Wars “vibroblades” are basically this.
I want to see a showdown between the hydraulic press guys and the sonic knife guys.
At an Edwards Pie factory I visited a high-pressure water jet knife was used to cut slices for individual servings such as served at fast food restaurants.
I appreciate the use for such a thing, and sort of want one, but I’d point out that for many of the examples in the video, you could also use a wire. That’s the Soviet space pencil of cheese cutting.
The soviet space pencil story is a myth … someone once spoke to a cosmonaut … graphite dust in zero g — very bad.
Lol properly sharpened penic doesn’t make any dustl. Anyway, graphite doesn’t even burn (try it with a lighter for yourself) so the myth of soviet space penicl myth is a myth. Americans wasted money (like they do now with Artemis) while Russians were very pragmatic.
No money was wasted, the Fisher pen company spent a bunch money developing a pen that would write in space. People loved the pen and the investment in RD paired for itself many times over. NASA got all there pens for free and the government didn’t have to pay a cent.
Stop making things up
Solid graphite requires a relatively high temperature to burn, but graphite dust is absolutely flammable, and is in fact explosive: https://www.inchem.org/documents/icsc/icsc/eics0893.htm
It’s a good analogy for what he’s saying and everyone understands what it is meant to mean
Ever heared if grease pencils?
I saved a dukane ultrasonic from the trash heap. Its 25 KHZ at ridiculous kw rating and I wasn’t sure what to do with it. Now I can set it up in the kitchen and cut pizza, pie, and all the other foods with it. Yay! It is 240VAC at 40 amp.
At that power level you could just use your skilsaw for the pizza.
Make a vibro-sword with it like I said in my other comment. Make a youtube video of you chopping pumpkins
Wait…what?
I have only been on a few food production lines, but cutting was always done with a water jet. No media of course, just distilled water.
Actually, that technically isn’t true, one place used steam jets for cutting.
I guess there might be times when an ultrasonic knife would be better, but water jet cutting is likely way more common.
I love to learn about these technologies, but it’s difficult to distill any knowledge from these videos. The 30-second clips are created to catch the eye of potential customers at a trade show, but they don’t explain much. A simple synced side by side on each cut of different items would be ideal to show off the technology.
That was your regular HAD writer filling his quota for the day.
This site is going down in quality since a few years …
I’ve seen some variation of this comment for the past 15 or so years that I’ve been reading hackaday. Truly authentic old-man-shouting-at-clouds sentiment.
Instead of regurgitating the same tired complaints, maybe you could write up an article for HaD that would satisfy your lofty requirements.
What’s to understand about vibrating a blade with an ultrasonic transducer?
It’s an interesting technique / solution to a problem and that’s part of the point of this site – seeing solutions or idea you might not have known about.
I’d like to know which axis to vibrate. For the purpose of building kitchen knife upgrade
i remember there was a different tech with a porous knife that would push air out constantly. Is there a comparison of those two techs?
I worked at a company (Ultrasion) where this technology was used to melt the plastic pellets in injection machines (so the plastic melts just-in-time, rather than slowly as it advances a heated barrel with a screw).
Now if only someone could miniaturize the technology into a normal sized chef’s knife. But that would take some kind of madman, or food geek… ;-)
If only…
https://www.aliexpress.com/i/3256807872985731.html?gatewayAdapt=4itemAdapt
How about a custom electric toothbrush head?
In 1987 i worked in a french compagny Mecasonic. And i had to develop th automatism of a machine to cut the cake with ultrasons. Th customer could cut the cake as soons as it go awway of the oven,. Cutting the cake when cold produced too many crumbs. Cutting it hot with a traditional knifer damaged it.
https://www.mecasonic.com/en/food-applications/
Does this cause cancer?
Just one of many reasons I need a vibro-blade….