Teardown Video: What’s Inside The Self-Solving Rubik’s Cube Robot

You can find all kinds of robots at Bay Area Maker Faire, but far and away the most interesting bot this year is the Self-Solving Rubik’s Cube built by [Takashi Kaburagi]. Gently mix up the colored sides of the cube, set it down for just a moment, and it will spring to life, sorting itself out again.

I arrived at [Takashi’s] booth at just the right moment: as the battery died. You can see the video I recorded of the battery swap process embedded below. The center tile on the white face of the cube is held on magnetically. Once removed, a single captive screw (nice touch!) is loosened to lift off the top side. From there a couple of lower corners are lifted out to expose the tiny lithium cell and the wire connector that links it to the robot.

Regular readers will remember seeing this robot when we featured it in September. We had trouble learning details about the project at the time, but since then Takashi has shared much more about what went into it. Going back to 2017, the build started with a much larger 3D-printed version of a cube. With proof of concept in hand, the design was modeled in CAD to ensure everything had a carefully planned place. The result is a hand-wired robotic core that feels like science fiction but is very, very real.

I love seeing all of the amazing robots on the grounds of the San Mateo County Event Center this weekend. There is a giant mech wandering the parking lot at the Faire. There’s a whole booth of heavy-metal quadruped bots the size of dogs. And if you’re not careful where you walk you’ll step on a scaled-down Mars rover. These are all incredible, out of this world builds and I love them. But the mental leap of moving traditional cube-solvers inside the cube itself, and the craftsmanship necessary to succeed, make this the most under-appreciated engineering at this year’s Maker Faire Bay Area. I feel lucky to have caught it during a teardown phase! Let’s take a look.

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Robot Solves Rubik’s Cube With One Hand Tied Behind Its Back

For all those who have complained about Rubik’s Cube solving robots in the past by dismissing purpose-built rigs that hold the cube in a non-anthropomorphic manner: checkmate.

The video below shows not only that a robot can solve the classic puzzle with mechanical hands, but it can also do it with just one of them – and that with only three fingers. The [Yamakawa] lab at the University of Tokyo built the high-speed manipulator to explore the kinds of fine motions that humans perform without even thinking about them. Their hand, guided by a 500-fps machine vision system, uses two opposing fingers to grip the lower part of the cube while using the other finger to flick the top face of the cube counterclockwise. The entire cube can also be rotated on the vertical axis, or flipped 90° at a time. Piecing these moves together lets the hand solve the cube with impressive speed; extra points for the little, “How’s that, human?” flick at the end.

It might not be the fastest cube solver, or one that’s built right into the cube itself, but there’s something about the dexterity of this hand that we really appreciate.

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Self-Solving Rubik’s Cube

Rubik’s Cube has been around for what seems like forever now, and has spawned an entire subculture devoted to solving the puzzle with automation. Most Rubik robots put the cube in a specially designed cradle bristling with actuators and sensors, and while those rigs are impressive, they don’t come close to this robotic Rubik solver built into the cube itself.

Fair warning that [Human Controller] doesn’t provide much detail on this build other than pictures; even translating the Japanese web page doesn’t offer much more information. But there are pictures, plus the video below, which reveal the engineering masterpiece encased within the standard sized Rubik’s cube. The internal mechanism of the original cube had been replaced by a spherical assembly around which the cube’s faces rotate. The sphere, which appears to be 3D-printed, houses six motors and gear trains, along with a microcontroller board and what appear to be Hall sensor boards to detect the position of each face. Everything is wired up with magnet wire to keep bundles to a minimum size, and buried deep inside is a LiPo battery pack. A disassembly video offers further clues to this ingenious device’s inner workings.

Once the cube senses that it has been scrambled, it sets to work on the solution, walking all over the table in the process. It’s clearly not just recording the scrambling steps and playing them back in reverse; the video below shows far more moves to solve the cube than the 15 it took to scramble it.

While we’re always impressed by marvels of speed like this robot with a 637 millisecond solve time, putting everything needed to solve the cube inside it is a feat worth celebrating. Here’s hoping that a build log shows up soon to satisfy our need for details.

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Solving A Rubik’s Cube With Just Two Motors

We’ve all seen videos of Rubik’s cube champions who can solve the puzzle in less than 5 seconds. And there are cube-twisting robots that can solve the cube even faster, often in under a second. This Rubik’s cube solver is not one of those robots, but it’s still pretty cool.

The reason we like Dexter Industries’ “BricKuber” is not for its lightning speed — it takes a minute or two to solve the puzzle. What we like is the simplicity of the approach to manipulating the cube. Built from LEGO parts, including Mindstorms motors and a BrickPi controller, the BricKuber uses only two motors to work the cube. One motor powers a square turntable upon which the cube sits, while the other powers an arm that does double duty — it either clamps the cube so the turntable can rotate a layer, or it rakes the cube to flip it 90° on the turntable. With a Pi Cam overhead, the rig images all six faces, calculates a solution to the cube, and then flips and twists the cube to solve it. It’s simultaneously mind-boggling and strangely relaxing to watch.

All the code is open source, and we strongly suspect a similar and possibly faster robot could be built without the LEGO parts. You might even be able to build one with popsicle sticks and an Arduino.

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Robot Solves Rubik’s Cube In Just One Second

Some of the fastest Rubik’s cube solvers in the world have gotten down to a five second solve — which is quite an incredible feat for a human — but how about one second? Well, [Jay Flatland] and [Paul Rose] just built a robot that can do exactly that.

The robot uses four USB webcams, six stepper motors, and a 3D printed frame. The only modification to the Rubik’s cube are some holes drilled in the center pieces to allow the stepper motors to grip onto them with 3D printed attachments.

The software is running off a Linux machine which feeds the data into a Rubik’s cube algorithm for solving. In approximately one second — the cube is solved.

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