Making A Metal Hand Doorknob

Regular doorknobs are widely reviled for their bare simplicity, but by and large society has so many other problems that it never really comes up in day to day conversation. Fear not, however, for [Matthew] has created something altogether more special: a doorknob in the shape of his own outstretched hand.

The build was inspired by a similar doorknob at the WNDR museum in Chicago, and its one you can recreate yourself, too. It’s achieved through a multi-stage mold making process. [Matthew]’s first step was to make a flexible mold of his hand using Perfect Mold alginate material to do so.

Once solidified, [Matthew’s] hand was removed and the mold filled with wax. The wax duplicate of [Matthew]’s hand was then used to create an investment plaster mold for casting metal. Vents were added in the end of each fingertip in the mold to allow molten metal to effectively fill the entire cavity.

Once the investment mold was solid and dry, the wax was melted out and it was ready for casting. A propane furnace was used to melt the casting metal and fill the mold using a simple gravity casting method. [Matthew] ended up making two hands, one in aluminium and one in copper. Some cleanup with grinders and a wire wheel, and a replica of [Matthew]’s hand was in his hands!

The finished piece looks great attached to a door knob, and we’re sure it’s quite satisfying shaking hands with your hefty metal self every time you open the door. It bears noting that the same techniques can be used with 3D printing, too! If you pull off your own great home casting project, be sure to drop us a line. Video after the break.

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Leap Motion Controls Hands With No Glove

It isn’t uncommon to see a robot hand-controlled with a glove to mimic a user’s motion. [All Parts Combined] has a different method. Using a Leap Motion controller, he can record hand motions with no glove and then play them back to the robot hand at will. You can see the project in the video, below.

The project seems straightforward enough, but apparently, the Leap documentation isn’t the best. Since he worked it out, though, you might find the code useful.

An 8266 runs everything, although you could probably get by with less. The Leap provides more data than the hand has servos, so there was a bit of algorithm development.

We picked up a few tips about building flexible fingers using heated vinyl tubing. Never know when that’s going to come in handy — no pun intended. The cardboard construction isn’t going to be pretty, but a glove cover works well. You could probably 3D print something, too.

The Unity app will drive the hand live or can playback one of the five recorded routines. You can see how the record and playback work on the video.

This reminded us of another robot hand project, this one 3D printed. We’ve seen more traditional robot arms moving with a Leap before, too. Continue reading “Leap Motion Controls Hands With No Glove”

Meticulous Bionic Hand

[Will Cogley] is slowly but surely crafting a beautiful bionic hand. (Video, embedded below.) The sheer amount of engineering and thought that went into the design is incredible. Those who take their hands for granted often don’t consider the different ways that their digits can move. There is lateral movement, rotation, flexion, and extension. Generally, [Will] tries to design mechanisms with parts that can be 3D printed or sourced easily. This constrains the hand to things like servos, cable actuation, or direct drive.

However, the thumb has a particularly tricky range of motion. So for the thumb [Will] designed to use a worm geared approach to produce the flexing and extension motion of the thumb. These gears need to be machined in order to stand up to the load. A small side 3d printed gear that connects to the main worm gear is connected to a potentiometer to form the feedback loop. Since it isn’t bearing any load, it can be 3d printed. While there are hundreds of little tiny problems still left to fix, the big problems left are wire management, finalizing the IP (Interphalangeal) joints, and attaching the whole assembly to the forearm.

All the step files, significants amounts of research, and definitions are all on [Will’s] GitHub. If you’re looking into creating any sort of hand prosthetic, the research and attention [Will] has put into this is work incorporating into your project. We’ve seen bionic hands before as well asĀ aluminum finger replacements, but this is a whole hand with fantastic range and fidelity.

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Roller-Based Robot Hand Grasps

In a recent International Conference on Robotics and Automation paper, [Shenli Yaun] and some others from Stanford discuss the design of a roller-based robot hand that has many features that mimic the human hand. The key feature is that each of the three fingers has a roller with a small geared motor.

The rollers allowed the hand to change an object’s orientation without losing its grasp. Of course, this works well with spherical objects like a ball. But the video shows that it can manipulate other items like a 6-sided die, a water bottle, or even a piece of paper. By spreading the fingers it can even hold large objects you wouldn’t expect at first glance.

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Assistive Gloves Come In Pairs

We have to hand it to this team, their entry for the 2020 Hackaday Prize is a classic pincer maneuver. A team from [The University of Auckland] in New Zealand and [New Dexterity] is designing a couple of gloves for both rehabilitation and human augmentation. One style is a human-powered prosthetic for someone who has lost mobility in their hand. The other form uses soft robotics and Bluetooth control to move the thumb, fingers, and an extra thumb (!).

The human-powered exoskeleton places the user’s hand inside a cabled glove. When they are in place, they arch their shoulders and tighten an artificial tendon across their back, which pulls their hand close. To pull the fingers evenly, there is a differential box which ensures pressure goes where it is needed, naturally. Once they’ve gripped firmly, the cables stay locked, and they can relax their shoulders. Another big stretch and the cords relax.

In the soft-robotic model, a glove is covered in inflatable bladders. One set spreads the fingers, a vital physical therapy movement. Another bladder acts as a second thumb for keeping objects centered in the palm. A cable system draws the fingers closed like the previous glove, but to lock them they evacuate air from the bladders, so jamming layers retain their shape, like food in a vacuum bag.

We are excited to see what other handy inventions appear in this year’s Hackaday Prize, like the thumbMouse, or how about more assistive tech that uses hoverboards to help move people?

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Rolling Out A New Robot Arm

A lot of great scientific breakthroughs come through imitating nature, but technology often runs up against limits in certain areas. This is particularly evident in robotics, where it takes a lot of effort (and cost) to build a robot which can effectively manipulate heavy objects but not crush others which are more delicate. For that, a research group has looked outside of nature, developing a robotic grasper which uses omnidirectional wheels to grab various objects.

The robot hand is composed of three articulating fingers with fingertips which are able to actively manipulate the object that the hand is holding. With static fingertips, it is difficult to manipulate an object in the hand itself, but with the active surfaces at the fingertips it becomes easier to rotate the object without setting it down first or dropping it.

The project is much more than designing the robot hand itself, too. The robot uses calculated kinematics to manipulate the objects as well, but a second mode was also tried where the robot was able to “learn” how to handle the object it was given. The video linked below shows both modes in operation, with interesting results. If you prefer more biologically-inspired robot arms, though, there are always novel designs based on non-humans.

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Haptic Glove Controls Robot Hand Wirelessly

[Miller] wanted to practice a bit with some wireless modules and wound up creating a robotic hand he could teleoperate with the help of a haptic glove. It lookes highly reproducible, as you can see the video, below the break.

The glove uses an Arduino’s analog to digital converter to read some flex sensors. Commercial flex sensors are pretty expensive, so he experimented with some homemade sensors. The ones with tin foil and graphite didn’t work well, but using some bent can metal worked better despite not having good resolution.

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