Author: Dan Maloney

3307 Articles

Torque Testing 3D Printed Screws

December 3, 2024 by 18 Comments

Unless you’ve got a shop with a well-stocked hardware bin, it’s a trip to the hardware store when you need a special screw. But [Sanford Prime] has a different approach: he prints his hardware, at least for non-critical applications. Just how much abuse these plastic screws can withstand was an open question, though, until he did a little torque testing to find out.

To run the experiments, [Sanford]’s first stop was Harbor Freight, where he procured their cheapest digital torque adapter. The test fixture was similarly expedient — just a piece of wood with a hole drilled in it and a wrench holding a nut. The screws were FDM printed in PLA, ten in total, each identical in diameter, length, and thread pitch, but with differing wall thicknesses and gyroid infill percentages. Each was threaded into the captive nut and torqued with a 3/8″ ratchet wrench, with indicated torque at fastener failure recorded.

Perhaps unsurprisingly, overall strength was pretty low, amounting to only 11 inch-pounds (1.24 Nm) at the low end. The thicker the walls and the greater the infill percentage, the stronger the screws tended to be. The failures were almost universally in the threaded part of the fastener, with the exception being at the junction between the head and the shank of one screw. Since the screws were all printed vertically with their heads down on the print bed, all the failures were along the plane of printing. This prompted a separate test with a screw printed horizontally, which survived to a relatively whopping 145 in-lb, which is twice what the best of the other test group could manage.

[Sanford Prime] is careful to note that this is a rough experiment, and the results need to be taken with a large pinch of salt. There are plenty of sources of variability, not least of which is the fact that most of the measured torques were below the specified lower calibrated range for the torque tester used. Still, it’s a useful demonstration of the capabilities of 3D-printed threaded fasteners, and their limitations.

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Modular Breadboard Snaps You Into Benchtop Tidiness

December 2, 2024 by 27 Comments

Solderless breadboards are a fantastic tool for stirring the creative juices. In a few seconds, you can go from idea to prototype without ever touching the soldering iron. Unfortunately, the downside to this is that projects tend to expand to occupy all the available space on the breadboard, and the bench surrounding the project universally ends up cluttered with power supplies, meters, jumpers, and parts you’ve swapped in and out of the circuit.

In an attempt to tame this runaway mess, [Raph] came up with this neat modular breadboard system. It hearkens back to the all-in-one prototyping systems we greatly coveted when the whole concept of solderless breadboards was new and correspondingly unaffordable. Even today, combination breadboard and power supply systems command a pretty penny, so rolling your own might make good financial sense. [Raph] made his system modular, with 3D-printed frames that lock together using clever dovetail slots. The prototyping area snaps to an instrumentation panel, which includes two different power supplies and a digital volt-amp meter. This helps keep the bench clean since you don’t need to string leads all over the place. The separate bin for organizing jumpers and tidbits that snaps into the frame is a nice touch, too.

Want to roll your own? Not a problem, as [Raph] has thoughtfully made all the build files available. What’s more, they’re parametric so you can customize them to the breadboards you already have. The only suggestion we have would be that making this compatible with [Zack Freedman]’s Gridfinity system might be kind of cool, too.

Unique 3D Printer Has A Print Head With A Twist

December 2, 2024 by 26 Comments

If you’re used to thinking about 3D printing in Cartesian terms, prepare your brain for a bit of a twist with [Joshua Bird]’s 4-axis 3D printer that’s not quite like anything we’ve ever seen before.

The printer uses a rotary platform as a build plate, and has a linear rail and lead screw just outside the rim of the platform that serves as the Z axis. Where things get really interesting is the assembly that rides on the Z-axis, which [Joshua] calls a “Core R-Theta” mechanism. It’s an apt description, since as in a CoreXY motion system, it uses a pair of stepper motors and a continuous timing belt to achieve two axes of movement. However, rather than two linear axes, the motors can team up to move the whole print arm in and out along the radius of the build platform while also rotating the print head through almost 90 degrees.

The kinematic possibilities with this setup are really interesting. With the print head rotated perpendicular to the bed, it acts like a simple polar printer. But tilting the head allows you to print steep overhangs with no supports. [Joshua] printed a simple propeller as a demo, with the hub printed more or less traditionally while the blades are added with the head at steeper and steeper angles. As you can imagine, slicing is a bit of a mind-bender, and there are some practical problems such as print cooling, which [Joshua] addresses by piping in compressed air. You’ll want to see this in action, so check out the video below.

This is a fantastic bit of work, and hats off to [Joshua] for working through all the complexities to bring us the first really new thing we’ve seen in 3D printing is a long time.

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Homebrew Phosphorescence Detector Looks For The Glow In Everyday Objects

November 28, 2024 by 8 Comments

Spoiler alert: almond butter isn’t phosphorescent. But powdered milk is, at least to the limit of detection of this homebrew phosphorescence detector.

Why spend a bunch of time and money on such a thing? The obvious answer is “Why not?”, but more specifically, when [lcamtuf]’s son took a shine (lol) to making phosphorescent compounds, it just seemed natural for dad to tag along in his own way. The basic concept of the detector is to build a light-tight test chamber that can be periodically and briefly flooded with UV light, charging up the putatively phosphorescent compounds within. A high-speed photodiode is then used to detect the afterglow, which can be quantified and displayed.

The analog end of the circuit was the far fussier end of the design, with a high-speed transimpedance amplifier to provide the needed current gain. Another scaling amp and a low-pass filter boosts and cleans up the signal for a 14-bit ADC. [lcamtuf] went to great lengths to make the front end as low-noise as possible, including ferrite beads and short leads to prevent picking up RF interference. The digital side has an AVR microcontroller that talks to the ADC and runs an LCD panel, plus switches the 340 nm LEDs on and off rapidly via a low gate capacitance MOSFET.

Unfortunately, not many things found randomly around the average home are all that phosphorescent. We’re not sure what [lcamtuf] tried other than the aforementioned foodstuffs, but we’d have thought something like table salt would do the trick, at least the iodized stuff. But no matter, the lessons learned along the way were worth the trip.

A Look Under The Hood Of Intermediate Frequency Transformers

November 27, 2024 by 11 Comments

If you’ve been tearing electronic devices apart for long enough, you’ll know that the old gear had just as many mysteries within as the newer stuff. The parts back then were bigger, of course, but often just as inscrutable as the SMD parts that populate boards today. And the one part that always baffled us back in the days of transistor radios and personal cassette players was those little silver boxes with a hole in the top and the colorful plug with an inviting screwdriver slot.

We’re talking about subminiature intermediate-frequency transformers, of course, and while we knew their purpose in general terms back then and never to fiddle with them, we never really bothered to look inside one. This teardown of various IF transformers by [Unrelated Activities] makes up somewhat for that shameful lack of curiosity. The video lacks narration, relying on captions to get the point across that these once-ubiquitous components were a pretty diverse lot despite their outward similarities. Most had a metal shell protecting a form around which one or more coils of fine magnet wire were wrapped. Some had tiny capacitors wired in parallel with one of the coils, too.

Perhaps the most obvious feature of these IF transformers was their tunability, thanks to a ferrite cup or slug around the central core and coils. The threaded slug allowed the inductance of the system to be changed with the turn of a screwdriver, preferably a plastic one. [Unrelated] demonstrates this with a NanoVNA using a nominal 10.7-MHz IFT, probably from an FM receiver. The transformer was tunable over a 4-MHz range.

Sure, IFTs like these are still made, and they’re not that hard to find if you know where to look. But they are certainly less common than they used to be, and seeing what’s under the hood scratches an itch we didn’t even realize we had.

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DIY Pipe Inspector Goes Where No Bot Has Gone Before

November 27, 2024 by 7 Comments

If you think your job sucks, be grateful you’re not this homebrew sewer inspection robot.

Before anyone gets upset, yes we know what [Stargate System] built here isn’t a robot at all; it’s more of a remotely operated vehicle. That doesn’t take away from the fact that this is a very cool build, especially since it has to work in one of the least hospitable and most unpleasant environments possible. The backstory of this project is that the sewer on a 50-year-old house kept backing up, and efforts to clear it only temporarily solved the problem. The cast iron lateral line was reconfigured at some point in its history to include a 120-degree bend, which left a blind spot for the camera used by a sewer inspection service. What’s worse, the bend was close to a joint where a line that once allowed gutters and foundation drains access to the sewer.

To better visualize the problem, [Stargate] turned to his experience building bots to whip up something for the job. The bot had to be able to fit into the pipe and short enough to make the turn, plus it needed to be — erm, waterproof. It also needed to carry a camera and a light, and to be powered and controlled from the other end of the line. Most of the body of the bot, including the hull and the driving gear, was 3D printed from ABS, which allowed the seams to be sealed with acetone later. The drive tracks were only added after the original wheels didn’t perform well in testing. Controlling the gear motors and camera was up to a Raspberry Pi Zero, chosen mostly due to space constraints. An Ethernet shield provided connectivity to the surface over a Cat5 cable, and a homebrew PoE system provided power.

As interesting as the construction details were, the real treat is the down-hole footage. It’s not too graphic, but the blockage is pretty gnarly. We also greatly appreciated the field-expedient chain flail [Stargate] whipped up to bust up the big chunks of yuck and get the pipe back in shape. He did a little bit of robo-spelunking, too, as you do.

And no, this isn’t the only sewer bot we’ve ever featured.

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Retrotechtacular: The Deadly Shipmate

November 27, 2024 by 33 Comments

During World War II, shipboard life in the United States Navy was a gamble. No matter which theater of operations you found yourself in, the enemy was all around on land, sea, and air, ready to deliver a fatal blow and send your ship to the bottom. Fast forward a couple of decades and Navy life was just as hazardous but in a different way, as this Navy training film on the shipboard hazards of low-voltage electricity makes amply clear.

With the suitably scary title “115 Volts: A Deadly Shipmate,” the 1960 film details the many and various ways sailors could meet an untimely end, most of which seemed to circle back to attempts to make shipboard life a little more tolerable. The film centers not on the risks of a ship’s high-voltage installations, but rather the more familiar AC sockets used for appliances and lighting around most ships. The “familiarity breeds contempt” argument rings a touch hollow; given that most of these sailors appear to be in their 20s and 30s and rural electrification in the US was still only partially complete through the 1970s, chances are good that at least some of these sailors came from farms that still used kerosene lamps. But the point stands that plugging an unauthorized appliance into an outlet on a metal ship in a saltwater environment is a recipe for being the subject of a telegram back home.

The film shows just how dangerous mains voltage can be through a series of vignettes, many of which seem contrived but which were probably all too real to sailors in 1960. Many of the scenarios are service-specific, but a few bear keeping in mind around the house. Of particular note is drilling through a bulkhead and into a conduit; we’ve come perilously close to meeting the same end as the hapless Electrician’s Mate in the film doing much the same thing at home. As for up-cycling a discarded electric fan, all we can say is even brand new, that thing looks remarkably deadly.

The fact that they kept killing the same fellow over and over for each of these demonstrations doesn’t detract much from the central message: follow orders and you’ll probably stay alive. In an environment like that, it’s probably not bad advice.

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