Apr. 16, 2016 | By Alec

3D printed weapons are the source of much controversy and disagreement within the 3D printing community, but we are pretty sure that everyone will agree that the latest creation by Portuguese engineer João Duarte is extremely cool: a 3D printed hidden sliding blade, taken directly from the very successful Assassin’s Creed IV: Black Flag video game. What’s more, he has shared his designs online for free, so we can all recreate this amazing assassin’s weapon from Edward Kenway, the world’s coolest pirate.

As you might remember, we’ve already seen a number of amazing 3D printing projects from the mind of João Duarte. A young electrical and electronics engineer from Algarve, Portugal, who absolutely loves technology, he is one of the founders of the Faro eLab Hackerspace. “I've recently entered the 3D printing world by building my own Prusa i3 and so far I've been learning and evolving a lot,’ he previously told us. He previously shared this amazing glow-in-the-dark 3D printed DNA Helix lamp with us, and even a 3D printed ion thruster.

Though he regularly works on very interesting projects, he explains there is one thing that has been on his agenda for a very long time: A hidden blade from Assassin's Creed, though he won’t be the first to make one. “There are a lot of hidden blades online, and people have been making amazing designs for a long time, but I've always felt that there wasn't much info on how to build them and how to adjust them,” he says of other designs. “Few people actually share their design with the web, and among those, even fewer actually teach you how to assemble it.”

That, in a nutshell, is what João has decided to share, and it is a very fun project indeed. Consisting of just a few 3D printed parts, some screws, nuts, glue and two rubber bands, it’s also definitely doable for the average maker. The design visible above was designed on the web-based TinkerCAD software, and completely looks the part. Of course, every new Assassin’s Creed release features another design, João simply felt that the ACIV Black Flag design was absolutely amazing. “Maybe because he was a pirate, maybe because there is a skull, I don't know. The thing is, I thought if I was gonna draw inspiration from any blade, it would be his,” he explains. Design ques were mostly taken from the official replace, along with a healthy helping of creativity.

And as you can see in the clip below, it does actually shoot out like a hidden blade should. To create that function, João simply copied the often used OTF (out-to-front) knife mechanism of existing blades. “The secret is the springs or in this case, rubber bands, when activated, they will release the accumulated energy onto the blade, making it slide out or slide in the casing. The rubber band connects two parts, called "sliders", one is on the back and is responsible for pushing the blade out, and another is on the front and it's the one that pulls the blade back in,” he explains. “Then there are 2 locks that keep the blade in place either when its retracted or deployed Finally there is another piece that also slides inside the mechanism, and it's responsible for keeping the tension of the elastic band.”

It’s quite a clever mechanism, but obviously requires quite a few 3D printed parts. All of João’s designs can be downloaded on Instructables here. You’ll see that there are in fact two versions: the standard version, and the more complex wrist-activated sliding version (at the bottom of the page). This version will actually work with an activation wheel that shoots out the knife when wrist pressure is exerted onto it. Cool, but more difficult to get right –  but you might like the challenge. If you opt for the latter, you’ll also need some strong nylon wire and an additional rubber band.

Both, however, were 3D printed on João’s DIY Prusa I3 Rework. “I was careful during the design stage in order to always be able to print all parts using a small bed like 200 mm x 200 mm (for example max. Prusa I3 printing area),” he explains. This might require some part rotation to make it fit. To get the color scheme right, he mainly used Silver and Gold PLA filaments, but this is obviously open for interpretation. “The printing settings were pretty normal, though some parts require more infill because they will be subjected to mechanical forces. So on average 40% infill, 0.2 mm of layer height, 1.2 mm shell thickness and a speed of 50 mm/s. My Prusa I3 nozzle size is 0.4 mm,” he explains. Some parts do requires support structures. All in all, 3D printing took about nine hours.

But of course a springing blade mechanism requires a lot more work than simply turning on your 3D printer. “The trick to get a 3D printed hidden blade working is actually sanding the parts. Depending on the 3D printer, on the settings, on the material, no parts come out with exact same size, so either there are going to be loose pieces or tight pieces,” he explains. Most will probably be too tight, which will create too much friction for the rubber bands to overcome, so carefully sand each and every part extensively – until everything can slide onto each other nicely and freely. If you feel any friction, you’re not ready yet.

If you have the patience to properly clean and sand all those separate parts, you simply have to assemble everything. As there are a lot of moving parts involved in a very confined space, make sure you carefully follow João’s tutorial on Instructables. While it is a bit of work, the results are extremely cool and look very dangerous indeed. Perfect for Comic-Con.



Posted in 3D Printing Application



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Ethan .I. Vadney wrote at 10/14/2018 7:15:39 PM:

would this hidden blade be able to be printed in metal? or only in plastic it shal work?

Nelson Neves wrote at 4/21/2016 12:02:08 PM:

Awesome work João, congrats! ps: the "glow-in-the-dark 3D printed DNA Helix lamp" link is not correct, it should point here: http://www.3ders.org/articles/20150929-maker-develops-3d-printed-ion-thruster-shares-files.html

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