Flexures Make Robotic Fingers Simpler To Print

July 16, 2024 by Dan Maloney 6 Comments

Designing an anthropomorphic robotic hand seems to make a lot of sense — right up until the point that you realize just how complex the human hand is. What works well in bone and sinew often doesn’t translate well to servos and sensors, and even building a single mechanical finger can require dozens of parts.

Or, if you’re as clever about things as [Adrian Perez] is, only one part. His print-in-place robotic finger, adorably dubbed “Fingie,” is a huge step toward simplifying anthropomorphic manipulators. Fingie is printed in PLA and uses flexures for the three main joints of the finger, each of which consists of two separate and opposed coil springs. The flexures allow the phalanges to bend relative to each other in response to the motion of three separate tendons that extend through a channel on the palmar aspect of the finger, very much like the real thing.

The flexures eliminate the need for bearings at each joint and greatly decrease the complexity of the finger, but the model isn’t perfect. As [Adrian] points out, the off-center attachment for the tendons makes the finger tend to curl when the joints are in flexion, which isn’t how real fingers work. That should be a pretty easy fix, though. And while we appreciate the “one and done” nature of this print, we’d almost like to see the strap-like print-in-place tendons replaced with pieces of PLA filament added as a post-processing step, to make the finger more compact and perhaps easier to control.

Despite the shortcomings, and keeping in mind that this is clearly a proof of concept, we really like where [Adrian] is going with this, and we’re looking forward to seeing a hand with five Fingies, or four Fingies and a Thumbie. It stands to be vastly simpler than something like [Will Cogley]’s biomimetic hand, which while an absolute masterpiece of design, is pretty daunting for most of us to reproduce.

Continue reading “Flexures Make Robotic Fingers Simpler To Print” →

3D Printed Fidget Knife Snaps Back And Forth All Day Long

May 8, 2024 by Donald Papp 31 Comments

Fidget toys all have a satisfying mechanical action to engage with, and [uhltimate]’s OTF (out the front) “fidget knife” model provides that in spades. The model snaps open and closed thanks to a clever arrangement of springs and latches contained in only three printed pieces.

Here’s how it works: at rest, the mock blade (orange in the image above) is latched in the closed position. As one presses the slider forward, the bottom spring begins to pull up against the blade until it moves far enough to release the latch. When the latch is released, the tension built up in the spring propels the blade outward where it again latches in the open position. Retraction is the same essential process, just in the opposite direction (and using a latch on the opposite side of the blade, which faces the other direction.)

As you may imagine, effective operation depends on the material. The model is designed to be printed in PLA, but [uhltimate] also provides a part variation with a stiffer spring for those who find that basic model isn’t quite up to the task for whatever reason. Smooth surfaces are also helpful for hitch-free operation, but lubrication shouldn’t be necessary.

If this sort of thing is up your alley, don’t miss the satisfying snap action of this 3D printed toggle mechanism, either!

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Spooky Noise Box Plays War Drums

September 20, 2023 by Kristina Panos 6 Comments

What do you have cooked up to scare trick-or-treaters this Halloween? We humbly suggest adding in some type of noise box, especially one like this offering from [Paisley Computer] that uses reverb and other effects to achieve chilling, thrilling sounds.

As you can see, this instrument is essentially a bunch of doodads affixed to and through a cigar box. And as you’ll hear in the first video after the break, the various rubber bands make great drum sounds. The springs are nice, too, but our personal favorite has to be the head massager thing. Shhhing!

Inside the box you’ll find a guitar jack and some piezos glued to the underside of the top surface, but you’ll also find springs mounted across the inside that add to the resonance of the cigar box.

You can use either an interface and DAW or an effects pedal chain to really make things freaky, and [Paisley Computer] does a showdown between Focusrite interface versus various stomp pedals in the second video. In the third video, we learn how to make one of our own.

Do you like the idea of a spring reverb? How about a really big one that sounds sort of Satanic?

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Spooky Noise Box Has Post-Halloween Potential

September 5, 2023 by Kristina Panos 8 Comments

There’s more than one way to scare people on Halloween. Sure, there’s always the low-brow jump scare, but that will generally just annoy the person and possibly cause a heart attack. No, what you need is a sustained soundscape of hellish audio. And where does one find hellish audio? Well, you make your own with a spooky-sounds noise box.

And no, we’re not talking about a soundboard that goes ‘boo’ and ‘ooo-OOO-oooh’ and whatnot. This is a full-on DIY instrument that has potential beyond Halloween. Essentially, the wooden box takes input vibrations from various doodads, and these vibrations are picked up by a piezo disk or two glued to the underside of the lid. The piezos are wired up to a 3.5 mm jack, which runs out to the PC and [SvartalfarQc]’s favorite Digital Audio Workstation (DAW). From there, it’s just a matter of playing around with the sounds — looping them, running them through various instrument voices, adding effects, and so on.

We love the the things that [SvartalfarQc] came up with, including a wind-up walking heart thing, a retractable badge holder, and that noise box mainstay, a sproingy doorstop.

We all know piezos are awesome, but have you ever considered that they can be used to digitize old wax cylinder recordings?

The Voltaic Pile: Building The First Battery

May 25, 2023 by Bryan Cockfield 11 Comments

In the technologically-underpinned modern world, most of us interact with a battery of some sort every day. Whether that’s the starter battery in a car, the lithium battery in a phone, or even just the coin cell battery in a wrist watch, batteries underpin a lot of what makes society possible now. Not so in the early 1800s when chemists and physicists were first building and experimenting with batteries. And those batteries were enormous, non-rechargable, and fairly fragile to boot. Not something suited for powering much of anything, but if you want to explore what it would have been like to use one of these devices, follow along with [Christopher]’s build of a voltaic pile. Continue reading “The Voltaic Pile: Building The First Battery” →

Tiny Palm-Sized Crossbow Build Is Cute And Dangerous

November 17, 2022 by Lewin Day 17 Comments

Crossbows were a major development in the history of weaponry. They enabled lesser-skilled soldiers to shoot arrows at great speed in a compact form-factor. You can now build your own tiny version, thanks to this creation from [Maciej Nowak].

The main body of the crossbow was cut from a piece of aluminium bar stock, being shaped with an angle grinder. A slot was then machined to mount the crossbar and pulleys. A round piece of aluminium tube serves as a spring holder, and the spring is tensioned via pulling back a length of sailing rope to rest on a latch. The latch is released by a small trigger, just like on a full-size crossbow.

The arrows (or bolts, more typically) were made by machining skewers and giving them hard metal tips cut from nails. This enables them to penetrate apples, and presumably other fruits. They fly straight enough to reliably hit a target from a meter or two away.

We’ve seen other crossbow builds before, like this one that fires cannonballs! Just be careful where you aim, and don’t get yourself or anyone else hurt.

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Mouse Finds New Home In Pinball Machine

October 3, 2022 by Bryan Cockfield 14 Comments

Restoring pinball machines is an excellent hobby, and can even be more than that as we see businesses like bars and museums focusing on them as a main attraction. There’s all kinds of intrigue to be found, from esoteric mechanical systems to classic electronics and unique artwork. For those building new pinball machines, though, one way to bypass a lot of the hassle of finding antiquated parts is to build a digital machine with an analog feel, like this machine which repurposes a computer mouse in an interesting way.

One of the important design considerations with a more modern system like this is to preserve the mechanical components that the player interacts with, in this case the plunger. This pinball machine is really just a large screen driven by a computer, but the plunger is a spring-loaded one from an old analog machine. Attached to the end of the plunger inside the cabinet is a cloth strap which passes underneath an old optical mouse. When the plunger is pulled and released, the mouse registers the position of the plunger and sends that information to the computer controlling the pinball display.

We really appreciate a KISS-style design like this in general. Mice are a proven, reliable technology and the metal components of the plunger are unlikely to ever wear out, which means that at least this part of the new pinball machine is unlikely to need much maintenance over the lifespan of the cabinet itself. For other ways of preserving the original feel of old machines, take a look at this build which incorporates all kinds of tricks within a MAME cabinet.