Dropping Marbles With Millisecond Accuracy

October 31, 2022 by Danie Conradie 40 Comments

All eight version of the drop mechanism — The road to the perfect marble dropper

[Martin] of the band [Wintergatan] is on his third quest to build the ultimate musical marble machine, and that means dropping marbles with maximum reliability and precision timing. Working through several iterations, and returning to first principles, he engineered a marble gate that can drop marbles with a timing standard deviation of 0 ms.

[Wintergatan]’s first two machines, Marble Machine and Marble Machine X gained significant attention, but their complexity was their undoing. As it turns out, a Rube Goldberg machine that makes music has a lot of potential failure points, and both machines proved too temperamental for the live stage. The third version, Marble Machine XT (T for “touring”) needed to be re-engineered for simplicity and reliability to be practical on the road.

[Martin] broke the marble machine concept down to its key components, of which the marble drop gate is the most obvious. Using a pair of contact microphones to record the moment of release and impact, he can measure the timing with precision. The first design had a standard deviation of 3.91 ms, which is not nearly enough for us to detect by ear, but is not up to [Martin]’s standard for “tight music”. It used a clock-type escapement mechanism, where the wheel is the release gate. After reviewing his measurement software and compensating for drift between the software components of his setup, the measured standard deviation was reduced by 1 ms. Another breakthrough was to remove any guiding surfaces below the gate and let gravity do all the work. The 8th iteration proved to be the winner and used the escapement arm as the drop gate and wheel to hold back the queue of marbles.

Coming from an arts background, [Martin] had to learn a lot of engineering lessons the hard way. Looking at the videos on his YouTube channel, it seems like he is taking the lessons to heart, and we look forward to seeing the Marble Machine XT come to life.

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3D Printed Heat Exchanger Uses Gyroid Infill For Cooling

October 31, 2022 by Danie Conradie 33 Comments

3D printing allows the physical manufacturing of some unique geometries that are simply not possible with other processes. If you design around these strengths, it is possible to create parts that significantly outperform more conventional alternatives. With this in mind [Advanced Engineering Solutions] created a metal 3D printed heat exchanger that is half the size and four times the efficiency of the one it was designed to replace. Video after the break.

Gyroid infill splits an internal volume in two, perfect for heat exchangers.

Made from an aluminum alloy using a Laser Powder Bed Fusion (LPBF) machine, the heat exchanger is intended to cool transmission oil on military helicopters by using fuel as the coolant. Looking somewhat similar to a Fabergé egg, it uses gyroid “infill” for the actual heat exchange part. An interesting characteristic of gyroids is that it creates two separate intermeshed volumes, making them perfect for this application.

It was printed in one piece, without any removable support, just an internal lattice that supports the gyroids at the inlet and outlets. The only post-processing required was threading and surface cleanup on the ports. Since metal 3D printing is still too expensive to really allow many iterative prints, a significant amount of design and simulation time was put in before the first print.

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Playing With The Power Of Full G-Code Control

October 30, 2022 by Danie Conradie 5 Comments

Slicing software needs to maintain a balance between ease-of-use and control, while handling handle any STL file you throw at it. If you eliminate the need to convert an existing 3D model, and create G-Code directly, you gain a lot of design freedom, at the cost of increased design effort. By taking advantage of this freedom and making it more accessible, [Andrew Gleadall] and [Dirk Leas] created the FullControl Design Library.

Each model is a mathematically generated extrusion path with a host of adjustable design parameters and print settings. This allows you to print things like a single-layer non-planar part, or 90° overhangs without any support (video after the break). The website was built using the python version of the original Excel-based FullControl Designer (unreleased at the time of writing), and threejs for the 3D visualization.

Go browse the library, play with some parameters and see what strikes your fancy. For ideas, help and updates, keep an eye on the FullControl Subreddit.

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Using Google Calendar For Machines To Keep Track Of Human Days

October 25, 2022 by Danie Conradie 10 Comments

Daily triggers for automation are simple in theory, unless it needs to keep track of the calendar that humans actually live by. Seasonal changes, shifting public holidays, or just being on vacation are all exceptions you may need to account for. [Jeremy Rode] likes using Google Calendar to stay on top of events, so he created CalendarScraper, a simple script to make his machines use it too.

Jeremy needed a timer for his spa heater that would reduce costs by only switching it on when his local time-of-use-based electricity rates were favorable. The rates varied based on the time of day, day of the week, and even seasons and public holidays. Instead of trying to set up everything manually in a cron job, he created a short and easy-to-modify JavaScript script to keep track of events on a Google Calendar.

We’ve seen some other projects that pull data from Google Calendar, including a recycling day reminder, and even a physical desktop calendar.

Lego Plays Electronic Drums

October 22, 2022 by Danie Conradie 15 Comments

The ability to quickly try out an idea, and then expand and develop it, is what rapid prototyping is all about. Although we tend to think of 3D printing when rapid prototyping is mentioned, [Brick Technology] reminds us of the power of Lego, as he rapidly builds and improves an electromechanical drum machine.

Using Lego Technic pieces, he starts with a simple music box-style drum with moveable pins that pluck on spring-loaded levers, which in turn hit piezoelectric discs. The electronics side is simple, with the discs wired to a Roland sound module from an existing electronic drum kit. With the ability to instantly adjust, add and remove pieces, he quickly finds and fixes the problem of getting eleven hammer mechanisms together and working smoothly.

To get around the limited pin space on the drum and increase the length and variation potential of the rhythms, [Brick Technology] moved to a belt design that can accommodate significantly more pins. He also added an electric motor and various gearbox ratios for consistent and adjustable tempo. Together with his water vortex ball machine, he makes us think our workshops probably need a few hundred Lego Technic pieces.

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Hackaday Prize 2022: Recycled Plastic Skateboard Decks Demonstrate Small-Scale Injection Molding

October 21, 2022 by Danie Conradie 25 Comments

Injection molding is usually focused on high-volume production, but that doesn’t always need to be the case. The Recycled Plastic Skateboard Deck project centers on the use of injection molding for a relatively low-volume production line using open-source tooling.

RPSD is part of the Precious Plastics ecosystem and uses the existing and open-source shredder and extruder to turn locally-sourced plastic waste into melted plastic. The core of the tooling is in the aluminum CNC-machined top, bottom, and edge mold sections bolted to a thick steel support structure that give the skateboard deck its shape. The edge section defines the deck’s perimeter, and 64 cartridge heaters are inserted into it to bring the mold up to temperature. The mold is mounted on a scissor lift mechanism to allow it to be aligned with the extruder, and temperature control electronics are housed in a laser-cut metal enclosure, which is bolted to the base of the mold structure.

To be clear, this is not a cheap way to make a couple of skateboard decks, but rather a way for small shops to do injection molded decks in-house. At ~$7500 for the components of this relatively large mold, excluding the extruder, you’d still have to sell quite a few decks to make it economically viable.

Although small-scale injection molding has become a lot more accessible, the cost of machined metal molds will remain high for the foreseeable future. However, if you only need small, flexible parts, you could probably do it for under $50 using 3D printed molds and silicone.

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Analog Tank Driving Simulator Patrols A Tiny Physical Landscape

October 18, 2022 by Danie Conradie 30 Comments

How do you build a practical tank-driving simulator in the 1970s, when 3D computer-generated graphics are still just a fantasy of the future? If you’re a European tanker school, the solution is to use a large CNC machine to drive a camera around a miniature terrain model (German, translated). In the video after the break, [Tom Scott] takes it for a test drive.

The old computer was replaced with a Raspberry Pi — The original computer was replaced with a Raspberry Pi

Developed in France, the simulator provided a safer and more cost-effective way for teaching new trainees the basics of driving Centurion, Leopard 2, or Panzer 68 tanks. The trainee sits in a realistic “cockpit” mounted on a hydraulically-operated motion platform, with a TV screen in front of his face, which is connected to a camera mounted on a large gantry-style CNC platform.

The camera’s lens is mounted just above a pivoting metal foot which slides across the 12 m-long terrain model and sends its angle to the hydraulic system. It will even alter the tank’s handling based on its current position on the model to simulate different surfaces like dirt, snow, or asphalt.

The last of these systems remained in use until 2004 at the military training center in Thun, Switzerland, before being saved by the Swiss Military Museum from being scrapped. The original 70s computer, electronics, and hydraulics finally gave out, so the museum undertook a complete refurbishment of the system to return it to working order for museum visitors. It was kept as original as possible, but parts for the original computer could not be found, so it was replaced with a Raspberry Pi and custom interface board.

Over three decades, these simulators probably trained a few thousand tank drivers, and even with limited technology did an excellent job of preparing trainees for the real thing. Besides providing training for operators, drivers and pilots, simulators are also just plain fun. We’ve seen some impressive home built simulator including a A-10 Warthog, an F-15 sim built from an actual wreckage, and even a starship’s bridge.

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