Tensioning 3D Prints For Lightweight, Strong Parts

August 6, 2023 by Bryan Cockfield 28 Comments

Desktop 3D printers have come a long way over the past decade. They’re now affordable for almost anyone, capable of printing in many diverse materials, and offer a level of rapid prototyping and development not feasible with other methods. That said, the fact that they are largely limited to printing different formulations of plastic means there are inherent physical limitations to what the machines are capable of, largely because they print almost exclusively in plastic. But augmenting prints with other building techniques, like this method for adding tensioning systems to 3D printed trusses can save weight and make otherwise unremarkable prints incredibly strong.

The build from [Jón Schone] of Proper Printing consists of printed modular sections of truss which can be connected together to make structural components of arbitrary length. To add strength to them without weight, a series of Kevlar threads are strung from one end of the truss to the other on the interior, and then tensioned by twisting the threads at one end. Similar to building with prestressed concrete, this method allows for stronger parts, longer spans, less building material, and lighter weight components. The latter of which is especially important here, because this method is planned for use to eventually build a 3D printer where the components need to be light and strong. In this build it’s being used to make a desk lamp with a hinged joint.

For other innovative 3D printer builds, [Jón] has plenty of interesting designs ranging from this dual extrusion system to this 3D printed wheel for a full-size passenger vehicle. There’s all kinds of interesting stuff going on at that channel and we’ll be on the edge of our seats waiting to see the 3D printer he builds using this tensioned truss system.

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Carbon Fiber And Kevlar Make This Linear Actuator Fast And Strong

May 3, 2023 by Dan Maloney 9 Comments

When it comes to the “build versus buy” question, “buy” almost always wins. The amount of time you have to put into building something is rarely justified, especially with a world of options available at the click of a mouse.

That’s not always the case, of course. These custom-made linear actuators are a perfect example of when building your own wins. For a planned ball-juggling robot, [Harrison Low] found himself in need of linear actuators with long throw distance, high speed, and stiff construction. Nothing commercially available checked all the boxes, so he set out to design his own.

A few design iterations later, [Harrison] arrived at the actuators you see in the video below. Built mainly from carbon fiber tubing and 3D-printed parts, the actuators have about 30 centimeters of throw, and thanks to their cable-drive design, they’re pretty fast — much faster than his earlier lead screw designs. The stiffness of the actuator comes by way of six bearings to guide the arm, arranged in two tiers of three, each offset by 60 degrees. Along with some clever eccentric spacers to fine-tune positioning, this design provides six points of contact that really lock the tube into place.

The cable drive system [Harrison] used is pretty neat too. A Kevlar kite string is attached to each end of the central tube and then through PTFE tubes to a pulley on an ODrive BLDC, which extends and retracts the actuator. It’s a clever design in that it keeps the weight of the motor away from the actuator, but it does have its problems, as [Harrison] admits. Still, the actuator works great, and it looks pretty cool while doing it. CAD and code are available if you want to roll your own.

These actuators are cool enough, but the real treat here will be the ball juggler [Harrison] is building. We’ve seen a few of those before, but this one looks like it’s going to be mighty impressive.

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The Real John Wick-Style Bullet Proof Suit

April 10, 2023 by Al Williams 55 Comments

If you’ve seen the John Wick movies, you’ve probably had to suspend your disbelief about many things, but the bulletproof suits are perhaps the hardest thing to swallow. They look like stylish suits but are impervious to just about anything at any range. What’s more is when you are hit, they seem to absorb all impact with no effect on the wearer at all.

You can keep running, firing, or karate kicking while the suit takes all of the bullets. You can even pull your jacket up over your face if you want to protect that million-dollar smile. Physics, of course, tells us that a suit like this is pretty much impossible. Except that they actually exist. Granted, the real-life suits don’t have the magic physics-defying powers of Mr. Wick’s suit, but if you have the cash, you can get a smart-looking suit that protects you from getting killed by a bullet.

Real Life, Part I

In the movies, the suits supposedly have Kevlar in them just like a real piece of ballistic body armor. The problem is, Kevlar is bulky. However, most of the real body armor you see — like a vest on a SWAT team operative — is made from Kevlar or similar ballistic fibers like Twaron, Goldflex, or Dyneema. They also have plates made of metal or ceramic. Continue reading “The Real John Wick-Style Bullet Proof Suit” →

3D Printed Material Might Replace Kevlar

July 29, 2021 by Al Williams 12 Comments

Prior to 1970, bulletproof vests were pretty iffy, with a history extending as far as the 1500s when there were attempts to make metal armor that was bulletproof. By the 20th century there was ballistic nylon, but it took kevlar to produce garments with real protection against projectile impact. Now a 3D printed nanomaterial might replace kevlar.

A group of scientists have published a paper that interconnected tetrakaidecahedrons made up of carbon struts that are arranged via two-photon lithography.

We know that tetrakaidecahedrons sound like a modern invention, but, in fact, they were proposed by Lord Kelvin in the 19th century as a shape that would allow things to be packed together with minimum surface area. Sometimes known as a Kelvin cell, the shape is used to model foam, among other things.

The 3D printing, in this case, is a form of lithography using precise lasers, so you probably won’t be making any of this on your Ender 3. However, the shape might have some other uses when applied to conventional 3D printing methods.

We’ve actually had an interest in the history of kevlar. Then again, kevlar isn’t the only game in town.

Stephanie Kwolek: Saving Lives With Kevlar

March 13, 2018 by Dan Maloney 41 Comments

Like most accidents, it happened in an instant that seemed to last an eternity. I had been felling trees for firewood all afternoon, and in the waning light of a cold November day, I was getting ready to call it quits. There was one tiny little white pine sapling left that I wanted to clear, no thicker than my arm. I walked over with my Stihl MS-290, with a brand new, razor sharp chain. I didn’t take this sapling seriously — my first mistake — and cut right through it rather than notching it. The tree fell safely, and I stood up with both hands on the saw. Somehow I lost my footing, swiveled, and struck my left knee hard with the still-running chainsaw. It kicked my knee back so hard that it knocked me to the ground.

In another world, that would likely have a been a fatal injury — I was alone, far from the house, and I would have had mere minutes to improvise a tourniquet before bleeding out. But as fate would have it, I was protected by my chainsaw chaps, full of long strands of the synthetic fiber Kevlar.

The chain ripped open the chaps, pulled the ultrastrong fibers out, and instantly jammed the saw. I walked away feeling very stupid, very lucky, and with not a scratch on me. Although I didn’t realize it at the time, I owed my life to Stephanie Kwolek.

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Ask Hackaday: What Can You Do With Origami?

February 26, 2017 by Dan Maloney 43 Comments

At some point, most of us have learned a little of the ancient art of origami. It’s a fascinating art form, and being able to create a recognizable model by simply folding paper in the right order can be hugely satisfying. Most of us move on to other pursuits once we master the classic crane model, but the mathematics behind origami can lead some practitioners past the pure art to more practical structures, like this folding ballistic barrier for law enforcement use.

The fifty-pound Kevlar and aluminum structure comes from Brigham Young University’s College of Mechanical Engineering, specifically from the Compliant Mechanisms Research program. Compliant mechanisms move by bending or deflecting rather than joints between discrete parts, and this ballistic shield is a great example. The mechanism is based on the Yoshimura crease pattern, which can be quickly modeled with a piece of paper. Scaling that up to a full-sized structure, light enough to be fielded but strong enough to stop a .44 Magnum round, was no mean feat. But as the video below shows, the prototype has a lot of potential.

Now it’s your turn: what applications have you seen for compliant mechanisms? Potential applications range in scale from MEMS linkages for microinjecting cells to huge antennas that unfurl in orbit. We’ve featured a few origami-like structures before, like this self-assembling robot or a folding quadcopter, but neither of these really rates as compliant. This elegant parabolic satellite antenna is more like it, though. There are applications for designing origami and a mathematical basis for the field; has anyone tried using these tools to design compliant structures? Sound off in the comments below.

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3D Printering: Aramid And Carbon Fiber Infused ABS

September 15, 2016 by Moritz Walter 43 Comments

Last week, we had a look at a carbon-infused PETG filament. This week, I’d like to show you two composites based on a more common thermoplastic in 3D printing: ABS. Among a whole lot of other engineering plastics, the french company Nanovia manufactures Kevlar-like aramid-fiber-infused and carbon-fiber-infused ABS 3D printing filaments. These materials promise tougher parts with less warping while being just as easy to print as regular ABS. Let’s check them out!

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