Robotic Hand v3.0

by embeddedjunkie, published

Robotic Hand v3.0 by embeddedjunkie Dec 24, 2011

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My first Robotic Hand (version 2.0) was designed with no 3d printer in mind. Version 2.0 had many shortfalls and difficulties. Since then, I've gotten a TOM and have learned how to design with its limitations and benefits in mind. I present to the 'verse Robotic Hand Version 3.0. Ver 3 requires less non-printable hardware, it requires less plastic to print, less printing time, less post-print work (very little sanding), and far less pull force is required to manipulate.

Version 3.0 Video of the Robot Hand in action:

Version 3.0 Flickr Set:

Version 2.0 for reference:


This model requires no scaling to compensate for shrinkage. At the very least you will only need to lightly sand the joints to get a smooth rotation along the axis. The thumb has been "frozen" in place for now. I'm planning a special re-design of the thumb out in Summer 2012. You can use Loctite blue to prevent screws/hex nuts from falling out by the constant movement. This model uses no metal bearings. The "hook" part is used to tether the fishing line to the tip of the finger. The "ring" is used to ease the model manipulation.

Stats: 32 plastic parts (10 distinct parts, the rest are duplicates). 23 M3x12 screws, 23 M3 hex nuts, 5 strands of fishing line, between 15 to 45 dental rubber bands (I used 3 bands per joint).

Questions? Comments? Kudos? :-)
Please don't forget to give attribution.

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Hi very good design.
Actually i would like to know what kind of nuts or screws you have used to assemble all the parts?

It's all good but I think the thumb needs work.

hey i super want to make this for my tech priest cosplay but a scaled up version that's maybe twice the size, how easily will this scale up?

I only ever printed this at the current scale. If you blindly scale all pieces, it could work. I'm unsure how the margins for error or tolerances would be affected. If you get this to work, let me know and I'll update my description.

this robotic hand is very meritorious!

What size dental rubber bands did you use? I see them in multiple sizes.

One of the images posted shows the packaging of the rubber bands I used. They are 1/4" diameter 'orange' elastics from TP orthodontics. I'm not sure why the images posted don't render properly anymore but you have to click 'view full size' to view them.

Hello, I am a hand prosthetic user, your hand seems reallt good, how do you control the fingers? By pulling the cables with the other hand?

You are correct. In the youtube video I am articulating the model with my other hand using fishing line. The next step is to house motors and electronics in a forearm enclosure.

Are you also going to share the SKP?

The google sketchup design file is up!

no way robots! neat

Part I is a pretty tough print - but, fishing line tied around an M3 nut would do the trick nicely.

I agree. I didn't anticipate how much room a knot on fishing line would take up. So, I'll have to design a finger tip end cap to house all that in.

Nice, you've got me thinking about Thing from the Adam's family on this one.

How has the fishing line been working for you? Have you had any problems with slack in the line when you let loose of the controls?

I've been asked to make a cable controlled version of Vogal and ABS filament just seems to have too much stretch in it over 2 or 3 feet to provide a quick response t
o the controls.

The fishing line has been great for my application. The fingers snap back in place as soon as you release a line. You can control the quickness of the snap with the number of rubber bands you attach at the joints. Also, you can adjust which joints fold first in a finger by adding or subtracting rubber bands at particular joints. It's simple but effective.