You’ve Got All Year To Print This Marble Machine Ornament For Your Christmas Tree

February 20, 2025 by Lewin Day 9 Comments

Most Christmas ornaments just hang there and look pretty. [Sean Hodgins] decided to whip up something altogether fancier and more mechanical. It’s a real working marble machine that hangs from the tree!

The build is simple enough, beginning with a translucent Christmas ornament shell readily available from most craft stores. Inside, a small motor spins a pinion, which turns a larger gear inside the body. As the larger gear spins, magnets embedded inside pick up steel balls from the base of the ornament and lift them up to the top. As they reach their zenith, they’re plucked off by a scoop, and then they roll down a spiral inside. As for power, [Sean] simply handled that with a couple of wires feeding the motor from a USB power bank. Just about any small battery pack would do fine.

The build is beautiful to watch and to listen to, with a gentle clacking as the balls circulate around. Files are on MakerWorld for the curious. We’ve featured some great Christmas decorations before, too. Video after the break.

Reconstructing 3D Objects With A Tiny Distance Sensor

February 20, 2025 by Lewin Day 6 Comments

There are a whole bunch of different ways to create 3D scans of objects these days. Researchers at the [UW Graphics Lab] have demonstrated how to use a small, cheap time-of-flight sensor to generate scans effectively.

Not yet perfect, but the technique does work…

The key is in how time-of-flight sensors work. They shoot out a distinct pulse of light, and then determine how long that pulse takes to bounce back. This allows them to perform a simple ranging calculation to determine how far they are from a surface or object.

However, in truth, these sensors aren’t measuring distance to a single point. They’re measuring the intensity of the received return pulse over time, called the “transient histogram”, and then processing it. If you use the full mathematical information in the histogram, rather than just the range figures, it’s possible to recreate 3D geometry as seen by the sensor, through the use of some neat mathematics and a neural network. It’s all explained in great detail in the research paper.

The technique isn’t perfect; there are some inconsistencies with what it captures and the true geometry of the objects its looking at. Still, the technique is young, and more work could refine its outputs further.

If you don’t mind getting messy, there are other neat scanning techniques out there—like using a camera and some milk.

Continue reading “Reconstructing 3D Objects With A Tiny Distance Sensor” →

Water Jets Will Carve Your Pumpkin

February 20, 2025 by Lewin Day 8 Comments

Carving pumpkins by hand is hot, sweaty, messy work, and a great way to slice your way into a critical artery. Why not let a water jet do it for you? It’ll be cleaner and more precise to boot, and [Jo_Journey] is here to show us how.

Obviously, you’ll need a water jet machine, there’s no getting around that. You’ll also still have to do the basic preparation of the pumpkin yourself—cutting a porthole into the top and mucking it out is your job. With that done, you must then mount the pumpkin on two metal rods which will be used to mount it in the water jet machine’s working area.

You can then create a vector file of your design, and use your chosen software to generate the G-code to run the water jet. [Jo_Journey] uses Scribe, and recommends cutting at a speed of around 200 in/min at low pressure. Remember, it’s pumpkin you’re cutting, not high-strength steel.

There is some inaccuracy, of course—your pumpkin’s surface is not a flat plane, after all—but the results are good enough for most Halloween-related purposes. Even despite the geometrical issues, though, [Jo_Journey] shows us that you can get pleasantly sharp edges on your design. That’s very hard to achieve by hand!

We do love a good holiday hack around these parts, even if it’s out of season. If you’ve been cooking up your own pumpkinous plans, don’t hesitate to let us know! Earlier is sometimes better—after all, who has time to hack together a project if you’ve just read about it on October 29?