Learn 15 Print-in-Place Mechanisms In 15 Minutes

3D printed in-place mechanisms and flexures, such as living hinges, are really neat when you can get them to print correctly. But how do you actually do that? YouTuber [Slant 3D] is here with a helpful video demonstrating the different kinds of springs and hinges (Video, embedded below) that can be printed reliably, and discusses some common pitfalls and areas to concentrate upon.

Living hinges are everywhere and have been used at least as long as humans have been around. The principle is simple enough; join two sections to move with a thinned section of material that, in small sections, is flexible enough to distort a few times without breaking off. The key section is “a few times”, as all materials will eventually fail due to overworking. However, if this thing is just a cheap plastic case around a low-cost product, that may not be a huge concern. The video shows a few ways to extend flexibility, such as spreading the bending load across multiple flexure elements to reduce the wear of individual parts, but that comes at the cost of compactness.

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DIY Driving Simulator Pedals

In the driving simulator community, setups can quickly grow ever more complicated and expensive, all in the quest for fidelity. For [CNCDan], rather than buy pedals off the shelf, he opted to build his own.

[Dan] has been using some commercial pedals alongside his own DIY steering wheel and the experience is rather lackluster in comparison. The build starts with some custom brackets. To save on cost, they are flat with tabs to let you know where to bend it in a vise. Additionally, rather than three sets of unique brackets, [Dan] made them all the same to save on cost. The clutch and throttle are a simple hall effect sensor with a spring to provide feedback. However, each bracket provides a set of spring mounting holes to adjust the curve. Change up the angle of the spring and you have a different curve. The brake pedal is different as rather than measure position, it measures force. A load cell is perfect for this. The HX711 load cell sensor board that [Dan] bought was only polling at 10hz. Lifting a pin from ground and bodging it to VDD puts the chip in 80hz, which is much more usable for a driving sim setup.

[Dan] also cleverly uses a 3d printed bushing without any walls as resistance for the pedal. Since the bushing is just the infill, the bushing stiffness is controlled by the infill percentage. Aluminum extrusion forms the base so [Dan] can adjust the exact pedal positions. To finish it off, a bog standard Arduino communicates to the PC as a game controller.

The project is on GitHub. Perhaps the next version will have active feedback, like this DIY pedal setup.

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A human hand is shown in the bottom right corner of the picture, holding one end of a pencil. A white, segmented, mechanical tentacle extends from the bottom left corner of the image and wraps around the other end of the pencil.

3D Printed Cable-Driven Mechanisms – Some Strings Attached

One of the most basic problems with robotic arms and similar systems is keeping the weight down, as more weight requires a more rigid frame and stronger actuators. Cable-driven systems are a classic solution, and a team of researchers from MIT and Zhejiang University recently shared some techniques for designing fully 3D printed cable-driven mechanisms.

The researchers developed a set of four primitive motion components: a bending component, a coil, screw-like, and a compressive component. These components can work together in series or parallel to make much more complicated structures. To demonstrate, the researchers designed a gripping tentacle, a bird’s claw, and a lizard-like walking robot, but much more complicated structures are certainly possible. Additionally, since the cable itself is printed, it can have extra features, such as a one-way ratcheting mechanism or bumps for haptic feedback.

These printed cables are the most novel aspect of the project, and required significant fine-tuning to work properly. To have an advantage over manually-assembled cable-driven systems, they needed to be print-in-place. This required special printer settings to avoid delamination between layers of the cable, cables sticking to other components, or cables getting stuck in the mechanism’s joints. After some experiments, the researchers found that nylon filament gives the best balance between cable strength and flexibility, while not adhering tightly to the PLA structure.

We’ve seen cable-driven systems here a few times before. If you’re interested in a deeper dive, we’ve covered that too.

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Tablet Suspension System Avoids Fatigue At Bedtime

You know how it is. You’re all cozy in bed but not quite ready to doze off. You’re reading Hackaday (Hackaday is your go-to bedtime reading material, right?) or you’re binge-watching your latest reality TV obsession on your tablet. You feel the tablet growing heavier and heavier as your arms fatigue from holding it inches above your face. You consider the embarrassment you’ll endure from explaining how you injured your nose as the danger of dropping the tablet gradually increases. The struggle is real.

[Will Dana] has been engineering his way out of this predicament for a few years now, and with the recent upgrade to his iPad suspension system he is maximizing his laziness, but not without putting in a fair amount of hard work first.

The first iteration of the device worked on a manual pulley system whereby an iPad was suspended from the ceiling over his bed on three cords. Pulling on a cord beside the bed would raise the bracket used for holding the iPad out of the way while not in use. This new iteration takes that pesky cord pulling out of the user’s hands, replacing it with a motorized winch. A spot of dark ink on one of the cords in combination with a light sensor helps to calibrate the system so that the ESP32 which controls it always knows the proper limits of operation.

Of course, if, like [Will], you’re using an ESP32, and your room is already fully controlled by a voice interface, you may as well integrate the two. After all, there is no sense in wasting precious energy by pressing buttons. Utter a simple command to Alexa once you’re tucked in, and it’s time for hands-free entertainment.

We’ve covered several of [Will]’s previous creations, such as his Motorized Relay Computer and Harry Potter-inspired Sorting Hat.

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Trekulator: A Reproduction Of The 1977 Star Trek Themed Calculator

A recent project over on Hackaday.io from [Michael Gardi] is Trekulator – Where No Maker Has Gone Before.

This is a fun build and [Michael] has done a very good job of emulating the original device. [Michael] used the Hackaday.io logging feature to log his progress. Starting in September 2024 he modeled the case, got his original hardware working, got the 7-segment display working, added support for sound, got the keypad working and mounted it, added the TFT display and mounted it, wired up the breadboard implementation, designed and implemented the PCBs, added some finishing touches, installed improved keys, and added a power socket back in March.

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DIY Soldering Tweezers, Extra Thrifty

It started when [Mitxela] was faced with about a hundred incorrectly-placed 0603 parts. Given that he already owned two TS101 soldering irons, a 3D printer, and knows how to use FreeCAD (he had just finished designing a custom TS101 holder) it didn’t take long to create cost-effective DIY soldering tweezers.

Two screws allow adjusting the irons to ensure the tips line up perfectly.

The result works great! The TS101 irons are a friction-fit and the hinge (designed using the that-looks-about-right method) worked out just fine on the first try. Considering two TS101 irons are still cheaper than any soldering tweezer he could find, and one can simply undock the TS101s as needed, we call this a solid win.

One feature we really like is being able to precisely adjust the depth of each iron relative to each other, so that the tips can be made to line up perfectly. A small screw and nut at the bottom end of each holder takes care of that. It’s a small but very thoughtful design feature.

Want to give it a try? The FreeCAD design file (and .stl model) is available from [Mitxela]’s project page. Just head to the bottom to find the links.

We’ve seen DIY soldering tweezers using USB soldering irons from eBay but the TS101 has a form factor that seems like a particularly good fit.

A New Mechanical Keyboard For An Old Computer

As computers age, a dedicated few work towards keeping some of the more interesting ones running. This is often a losing battle of sorts, as the relentless march of time comes for us all, human and machine alike. So as fewer and fewer of these machines remain new methods are needed to keep them running as best they can. [CallousCoder] demonstrates a way of building up a new keyboard for a Commodore 64 which both preserves the original look and feel of the retro computer but also adds some modern touches.

One of the main design differences between many computers of the 80s and modern computers is that the keyboard was often built in to the case of the computer itself. For this project, that means a custom 3D printed plate that can attach to the points where the original keyboard would have been mounted inside the case of the Commodore. [CallousCoder] is using a print from [Wolfgang] to get this done, and with the plate printed and a PCB for the keys it was time to start soldering. The keyboard uses modern switches and assembles like most modern keyboards do, with the exception of the unique layout for some of the C64 keys including a latching shift key, is fairly recognizable for anyone who has put together a mechanical keyboard before.

[CallousCoder] is using the original keycaps from a Commodore 64, so there is an additional step of adding a small adapter between the new switches and the old keycaps. But with that done and some amount of configuring, he has a modern keyboard that looks like the original. If you’re more a fan of the original hardware, though, you can always take an original C64 keyboard and convert it to USB to use it on your modern machines instead.

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