An Open Source Modular Flexure Construction Set

Flexures are one of those innocent-looking mechanisms that one finds inside practically any kind of consumer device. Providing constrained movements with small displacements, complete with controlled tension, they can be rather tricky to design. GrabCAD designer [Vyacheslav Popov] hails from Ukraine, and due to the current situation there, plans to sell a collection of flexure building blocks became difficult. In the end, [Vyacheslav] decided to generously release his work open source, for all to enjoy. This collection is quite extensive, looking like it could solve a huge variety of flexure design problems. (Links to the first three sets: Set00Set01Set02 but check the author’s collection page for many others)

It’s not just those super-cheap mechanisms in throw-away gadgets that leverage flexures, it’s much more. The Mars rovers use flexure-based suspension, scientific instruments (interferometers and the like) make use of them for small motions where specific axis constraints are needed, and finally, MEMS accelerometers and gyroscopes are based entirely upon them. We’re not even going to try to name examples of flexures in the natural world. They’re everywhere. And, now we’ve got some more design examples to use, so why not flex your flexure muscles and send one to the 3D printer and have a play?

We see flexures here quite a bit, like this nice demonstration of achievable accuracy. Flexures can make some delicious mechanisms, and neat 3D printable input devices.

Thanks to [Addison] for the tip!

See The Forbidden Cigarette Machine In Action

[Fraens] has been designing a number of fantastic 3D printed machines and making great videos that demonstrate how they work. The last installment was an automatic cigarette stuffing machine, and it’s got a number of pretty complex motions, and somehow manages to get the job done.

While [Fraens] usually uploads STL files for all of his machines, this one is forbidden! Selling automatic cigarette loaders is illegal in Europe, and it’s not clear how close to the legal edge posting them up on Thingiverse is. So until the legal dust settles, you’re going to have to be content with the fantastic video, also embedded below.

But honestly, the devil’s sticks aren’t good for your health anyway, and you’re probably just in it for the mechanicals. Think for a moment about the problem – you’ve got a hopper of tobacco fibers that all like to stick together, and you need to pack them into an easily squished lightweight paper tube. These tubes aren’t easy to handle either. The solution to both of these calls for solenoid-powered tappers that agitate both into place.

There’s also a 3D printed rack and pinion to do the pushing, and a cool stepper-driven revolver mechanism to put the empty papers into just the right place. The machine leans heavily on 3D printing, but also on simple hardware-store parts like aluminum and brass tubes. [Fraens]’s builds are always simple but simultaneously very slick, and you’ll learn a lot from watching it all go together.

And when you’re done, check out some others from [Fraens]. We’ve been impressed by his sewing machine, braiding machine, and even a power loom.

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A 3D Printed Marble Run Features Neat Elevator Linkage

There’s seldom anything as joyful and relaxing to watch as a simple marble run. Of course, the thing about letting marbles fall under gravity is that you eventually need to lift them back up again. The Marblevator has a mechanism that does just that.

Overall, the build features a relatively simple marble run. It consists of just six 3D printed ramps which the marble tumbles down in just a few seconds. However, the real magic is in the mechanism that restores the marbles from the bottom of the run all the way back to the top.

A motor turns a gear, which then rotates a crank leading to a multi-link rhombus. On one corner of the rhombus is a small protrusion with a magnet attached, which picks up the marbles from the bottom of the run. As the mechanism turns, the rhombus shifts and brings the marble-carrying arm to the top of the marble run. There, it’s grabbed by another magnet, which holds the marble for a moment before letting it drop back down through the run.

It’s a simple project that nonetheless would make a brilliant desk toy. It’s also a great way to learn about linkage analysis and designing such systems on your own. If you’re big into marble runs, you might also consider procedurally generating them. Video after the break.

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Hand-Cranked Doodler Made Using A 3D Printer

3D printers are great at creating complex geometry out of plastic, and that geometry can often pull off some impressive tricks. [DaveMakesStuff] found a way to generate geometry that draws 2D shapes with a pen and some fancy cams, and it’s really fun to watch.

The build is relatively simple. It consists of a frame which holds a 3D-printed cam turned by a hand crank. That cam controls the movement of a pen in two dimensions, letting it draw all manner of shapes. Videos on Reddit demonstrate it drawing squares, figure eights, and stars, while on YouTube, it writes the phrase “CAM I AM.”

According to [DaveMakesStuff], he figured out how to create the cams with “hours and hours of tedious CAD work.” We imagine there’s a way to do this with maths instead in parametric modelling software, and await such a build on the Hackaday tipsline. Those eager to recreate the build can explore the files on Thingiverse.

We’ve seen some great 3D-printed mechanisms before, too, like this zig-zag cam for a sewing machine. Video after the break.

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Cool Mechanism Day: Two-Way To One-Way

The internal mechanisms that are used in timepieces have always been fascinating to watch, and are often works of art in their own right. You don’t have to live in the Watch Valley in Switzerland to appreciate this art form. The mechanism highlighted here (from Mechanistic on YouTube) is a two-way to one-way geared coupler (video, embedded below) which can be found at the drive spring winding end of a typical mechanical wristwatch.  It is often attached to a heavily eccentrically mounted mass which drives the input gear in either direction, depending upon the motion of the wearer. Just a little regular movement is all that is needed to keep the spring nicely wound, so no forgetting to wind it in the morning hustle!

The idea is beautifully simple; A small sized input gear is driven by the mass, or winder, which drives a larger gear, the centre of which has a one-way clutch, which transmits the torque onwards to the output gear. The input side of the clutch also drives an identical unit, which picks up rotations in the opposite direct, and also drives the same larger output gear. So simple, and watching this super-sized device in operation really gives you an appreciation of how elegant such mechanisms are. Could it be useful in other applications? How about converting wind power to mechanically pump water in remote locations? Let us know your thoughts in the comments down below!

If you want to play with this yourselves, the source is downloadable from cults3d. Do check out some of the author’s other work!

We do like these super-sized mechanism demonstrators around here, like this 3D printed tourbillon, and here’s a little thing about the escapement mechanism that enables all this timekeeping with any accuracy.

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Light Painting With An 19th Century Inspired Plotter

The geometric chuck was a device that stacked up multiple rotating wheels that could vary their speed and their offset to a central shaft, in order to machine ornate designs using a lathe. It’s this piece of machining obscura from the 19th century that inspired this light painting build from [Ted Kinsman].

Rather than the complicated gears and wheels used in the distant past, [Ted] instead elected to use stepper motors. Three stepper motors are stacked on top of each other, each one able to rotate at an independent rate. The design only implements three steppers as the slip rings needed to send power and control signals to each stepper are prohibitively expensive.

An Arduino is programmed to run the show, changing the speed of each motor and thus the patterns the system generates. Put LEDs on the spinning plates, or install a pen to mark a piece of paper, and it’s possible to generate all manner of beautiful spirograph-like patterns. Vary the motor speeds or the positioning of the lights, and the patterns vary in turn.

It’s a fun build for light painting, with some great visuals produced. We also appreciate the use of the Arduino which makes varying the parameters far easier than having to change out gearsets in classical designs.

If you miss the old school spirograph, you can always build one out of Lego. Else, consider experimenting with other light painting techniques. If you’ve built a fancy rig of your own, be sure to let us know!

[Thanks to zit for the tip!]

This Dual Extrusion System Rocks

Dual extrusion systems for 3D printers have been around for quite a few years, but the additional cost, complexity, and hassle of printing with them have kept them off the workbenches of most hackers. [Jón Schone] from Proper Printing has now thrown his own hat in the ring, with a custom dual extrusion rocker system that can swap extruders without any additional actuators.

The two extruders are mounted on a spring-loaded rocker mechanism, which holds the inactive extruder up and away from the printing surface. Extruders are swapped by moving the carriage to either end of the x-axis, where the v-wheel rolls a ramp and pops the rocker over, putting the new extruder in the center line of the carriage. There are 3 wheels at the top of the carriage, but only two are in contact with the rail at any time. While this system is more complex than simply mounting two extruders side-by-side, it reduces the chances of the inactive nozzle oozing onto the parts or scraping across the surface. The height of each extruder can be adjusted with a screw,  and any horizontal offset between the nozzles is checked with a calibration procedure and corrected in the firmware. See the full video after the break.

[Jón] is offering the design files and modified firmware to perform this mod on your own Ender 3 Pro (though he notes other Creality printers should be compatible), but you’ll still need to source a control board with the additional stepper driver and heater output for the second extruder. This is yet another in a long list of hacks he’s performed on this popular entry-level printer, such as a modification that allows you to fold the machine up and take it on the go.

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