Rubik’s Cube Solving Robot

I took apart my old 3D printer to salvage its stepper motors. I started by getting one motor working, using the hardware I already had rather than buying a new set.

I tested one axis before moving on to coordinated motion. These tests let me work on individual turns before adding the complexity of the full mechanism.

I went through five frame designs to balance easy cube loading with a rigid mechanism.

The issueThe cube needed to go in and out without taking the whole robot apart, but the frame also had to hold it securely while the motors applied torque.

What changedI settled on a magnetic design that could come apart conveniently while staying sturdy enough to hold the cube during turns.

What I learnedEase of assembly and mechanical stiffness had to be designed together. The useful design was a compromise between the two.

Intermittent connections made troubleshooting much harder than it needed to be.

The issueCables would randomly stop working. An unreliable connection could make the same setup behave differently from one test to the next.

What I learnedReliable connections are part of the design, not just a detail to finish later. This experience inspired me to start designing my own PCBs.

I moved on to testing two axes with the full six-axis setup connected.

Testing all six axes brought the mechanism together, but getting every cube face to line up reliably was a much bigger challenge than getting one motor to turn.

Face alignment was one of the biggest problems in the build.

The issueMotors skipped steps, microstepping was not behaving as expected, and the frame was not secure enough. I traced the problems to incorrect stepper-driver settings, insufficient torque and frame movement.

What changedI refined the frame and optimized the motor-control code, with repeated tuning and testing to keep the commanded step counts consistent.

What I learnedA command to turn is not a guarantee that the face reaches the right position. Electrical settings, available torque and mechanical rigidity have to work together.

Reaching a first solve was the milestone that brought the motor tests, wiring and mechanism together. It also gave me a clearer view of what still needed to become more reliable.