Maker Creates Robot That Looks Just Like a Spool of Filament for 3D Printers

A spool of filament rests calmly on a shelf, looking exactly like the usual orange Prusament roll found in numerous 3D printers, yet it hides a little secret. Prusa wanted a one-of-a-kind gift and asked Matt Denton to transform a regular 2kg spool of filament into an out-of-the-ordinary remote-controlled robot dubbed SpoolBot, which you’d be hard-pressed to tell is actually a robot going for a little roll on its own power.

Denton started from scratch with a genuine Prusament spool and simply retained the outward appearance the same, which means it still has the orange filament wrapped around a center drum in a sloppy, but highly realistic pattern. One side of the spool is fixed, but the other side detaches with magnets to allow you to go in and make changes. Those black plastic ends are actually the pieces that move the spool; they are the driving wheels. Inside, everything is held together by an internal frame that prevents the entire structure from looking out of place.

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The whole device is powered by two geared DC motors from Pololu, each equipped with an encoder that tells the bot exactly what it’s doing and causes the drive wheels at the spool’s edges to turn. Batteries are put low to function as a counterbalance, ensuring that the entire assembly remains upright when the spool spins around its center. A DFRobot Romeo Mini ESP32-C3 board handles all of the control, and it works in tandem with a BNO085 IMU sensor to keep an eye on things and ensure the spool remains upright and stable. An RC receiver links to a simple handheld controller.

Movement is accomplished by a technique known as differential drive; in order to travel in a straight path, both motors must be moving at the same speed; however, varying the speeds results in pleasant smooth bends. The IMU monitors how far up and down and side to side it moves, and if it becomes unsteady, it slows down the motors to keep the whole thing from toppling over. Then there’s the gyro feedback, which effectively keeps the spool on track even when it’s on an uneven surface like a carpet. Several operating modes are available, allowing you to choose how the bot behaves. For example, you can keep it sitting in one location, have it follow a trail back to where it began, cruise along at a given speed, or even perform some beautiful spins at full or half speed.

The entire assembly required a lot of meticulous planning and engineering to get right; as you can see, the outer shell must be able to spin freely on the center hub, so it’s all about getting the bearings perfect so it travels smoothly. The insides of the spool are made up of 3D-printed elements in black PETG and orange PLA, which are held in place by a variety of ingenious components such as heat-set inlays and precision bolts. The wiring is neatly tucked away so that it does not interfere with the movement of the various components. It took around five weeks to complete the project, from designing it in CAD to printing the pieces and writing the code.

Matt Denton chose to be generous and share all of the build files and code with the world. You can get them on Printables and on GitHub, and there is even a video guide that shows you how to create one yourself, from installing the bearings to wrapping the filament around the central drum and calibrating the controller. Of course, like any decent robot, SpoolBot includes a couple googly eyes and a small indication to give it some personality as it rolls around the floor.
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