Nice day today, InMoov right hand has been featured on Thingiverse!
I wanted since a while to transform the wrist of the hand because of a lack of DOF. For to do that, I had to dismantle the whole hand...(again)  I decided last night to give it a go. Worked something in Blender after creating some gears with Openscad using "Parametric Herringbone and helical gears" from canadaduane in Thingiverse. Actually since it was the first time I used Openscad, it took me a while to figure out the whole thing.
I printed the parts this morning and made a test with the Arduino. I had to adjust some parts of course but the whole thing finally works. I will soon put the parts to download on Thingiverse.

Here are some pictures to illustrate the building of this new part.
After printing you should have five parts.  
Remove with pliers the support. Fix in the bracket the servo MG995. Use the Arduino to set it to 0 degree.

Use one of your spare actuator from your servo. Cut it and fix it to the small gear as shown. It shouldn't be oversized.
Grease the big gear before setting in "rotawrist2".
Drill and tight fit the gear to "rotawrist3" through "rotawrist2".

Use hot glue gun to position and fix "cableholderwrist1" to the top of the servo. This will help to guide the rods into the center hole.

Close the whole thing and tight the 3 screws on perimeter. Make a test run with your Aduino. This is the position you should have when your servo is at 180° for the left hand

Now it's time to glue "rotawrist1" to "robpart2V2". Once glued detach "rotawrist1" from "rotawrist2". Start running the rods from your servos up to each finger. (Use the Arduino to set your servos at 0 Degrees) Don't twist the rods and make sure the upper rods run through the upper parts of the fingers, run the lower rods through the lower parts of the fingers.
This is where you are going to test your patience and skills. I use twisers for to do the job.


  1. just wanted to let you know that you've got very sexy hands

  2. Nice work!
    As for your keyboard problem check this: http://en.wikipedia.org/wiki/Rollover_%28key%29
    Good luck with your project

    1. Thanks for the comment, some others have been suggesting the same idea and I have a rollover keyboard, but it seems like I can't use serialterm to use more keys at once through the Arduino Com. I'm in the process of building the arm at the moment more then trying to control. But for sure at some point I will have to dig that problem.

  3. Excellent design. You beat me to it! I'm in the process of building my robotic arm with a friend. We have a very similar way of using servos and braided fishing wire(Stainless Steel), although we are not using the horns to improve strenghth. We are using aluminium for the hand and arm. No where near complete. You have a better wrist movement that we will have to borrow. Ingenious design. Excellent!

    1. Ahh robots are born pieces by pieces. Thanks for the comment

  4. Just finished the pieces for the Right and Left wrists today - Saturday, June 30, 2012. Full printed versions each, one printed on a DLP printer and the other on a MakerBot Thing-O-Matic. Both printed extremely well. Good design with proportions and, support. I'd remind that where there may be stress buildup - in sharp corners - to create a small radius in your corners. Thanks for the work to follow your lead.

  5. I found out that drilling and fitting a screw from both sides adds stability to the rotational part of the wrist.

    In addition the new small gear is much to small for fixing it with screws to a horn. I just printed an ABS horn and glued the small gear to it. Finding the correct height requires some experimentation.

    And when using the HK15298 there are some small things to fix to make it fit correctly.

    Besides that the rotational wrist works fine for the HK15298.