YouTube lunatic designed and 3D printed a working mechanical calculator

Mechanical calculators are precise, fascinating gadgets that you wouldn’t think would take well to being 3D printed, but a YouTuber has proved that a pocket-sized unit can be made purely from plastic filament. YouTuber 3D all Workshop detailed his working, but limited, build in a recent video. If you’re familiar with the holy grail of palm-sized mechanical calculators, the Curta, also known as the “pepper mill,” you already have a working understanding of how this 3D-printed calculator works. As detailed in the video, Workshop’s 3D-printed mechanical calculator, like the Curta, relies on a more than 200-year-old component known as the Leibniz stepped drum, named for its inventor, German philosopher and mathematician Gottfried Wilhelm Leibniz. The core concept of the calculator’s central mechanism, like that of many other mechanical calculators, is the Leibniz drum’s teeth of different lengths. There are nine teeth per drum, representing values one through nine, while a zero setting engages none of them. Workshop’s 3D printed calculator can take inputs from 1 to 999, with one drum per digit. You use a lever to move a gear up the drum so that it only activates as many teeth as are needed for a particular number. The same concept is used to input values into the Curta, just in a much more precise manner - one of the big benefits of using machined aluminum over 3D printing filament. As a result of wanting to keep the 3D printed calc’s build palm-sized, the YouTuber was forced to restrict what it’s able to do. It can do addition, and the addition of a multi-wheel enables it to also do multiplication by simply performing multiple sequences of adding the same number. The Curta does multiplication in a similar manner, requiring a user to input their base number and the number of times they want to multiply by addition. Unlike the Curta, Workshop’s calculator can’t subtract, nor can it divide - as its creator explains, there simply wasn’t the room to get all those fiddly bits into a palm-sized device. It’s not clear how large it would have to be to add those functions, but if the 3x-sized 3D printed Curta is any indication - its creator said the increased size was necessary - it’d probably be quite large. Scaling down to Workshop’s tiny 3D printed calculator means plenty of issues were bound to arise, and they definitely did. “There were a lot of problems,” he noted, explaining that “even the tiniest inconsistencies when printing can cause problems.” If you’ve ever used a 3D filament printer, you know how often such inconsistencies pop up. Gears kept binding because of tight 3D-printing tolerances, while backlash (the play between mating mechanical parts) could throw the drums out of sync. Pieces kept breaking during redesigns, and even the vibrations from picking up and using the calculator were enough to disrupt its components. The YouTuber went through roughly 100 design iterations over the two-month project, finally addressing the problems with custom-designed 3D-printed springs and a ratchet mechanism that kept backlash from throwing the drums out of sync. All said, the final build ended up with 109 separate pieces, took 17 print-hours to complete, and used 90g of filament. Despite multiple calls on YouTube for 3D all Workshop to publish, or even sell, his design, he has yet to make it available, so no struggling through a day-long print job for a potentially brief moment playing with this one. In the meantime, you could 3D print the giant Curta, or if you have a couple grand lying around begging to be spent, try to get your hands on an original. ®