

Open-Source Library of CAD Designs for 3D-printed, Underactuated Robotic Hands - toothpickguy
http://www.eng.yale.edu/grablab/openhand

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Isamu
Underactuated robotics is a cool topic, but I hadn't heard of underactuated
hands before.

"The released hand designs feature tendon-driven underactuated fingers.
Underactuated hands have been shown to improve the generality of simple
grippers by adaptively conforming to the surface of objects without the
explicit need for sensors or complicated feedback systems. This design
paradigm separates the actuation and finger elements, enabling a greater
degree of customization."

"Based on the original SDM Hand, the Model T is the OpenHand Project's first
released hand design, initially introduced at ICRA 2013. the four
underactuated fingers are differentially coupled through a floating pulley
tree, allowing for equal force output on all finger contacts."

Anybody here take this course? [https://www.edx.org/course/underactuated-
robotics-mitx-6-832...](https://www.edx.org/course/underactuated-robotics-
mitx-6-832x) Is this ongoing?

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toothpickguy
The MIT underactuated robotics course actually deals with underactuated
robotics in terms of dynamics. Our hands considers underactuation from a
quasi-static perspective. The main take-away for our project/design is that
the final configuration of the hand is determined not only by the actuator
inputs, but also the fingers' interactions with the object and environment.

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Kliment
This makes me both very happy and very sad - happy because it's a brilliant
thing, sad because it's in a proprietary format that requires expensive closed
software to open and edit.

~~~
toothpickguy
I will provide exported STEP files soon, alongside the STL files. I used
Solidworks not only because it's the standard in our research lab, but also
because I couldn't do what I wanted with any other CAD package. My source
files are actually highly parametric, with extensive use of a set of global
variables to help me adapt the designs for different printer settings and
different system design constraints without having to rebuild the CAD every
single time. The closest open-source solution I could find with similar
functionality was OpenSCAD, but (imo) it's not mature enough to handle
assemblies or more detailed models, and I'd bet that far fewer people have
ever tried OpenSCAD than Solidworks.

If you can suggest an alternative open-source CAD package, not just file
format, I'd be happy to look into it. Thanks for the interest!

~~~
starseeker
The other two projects that leap to mind for open source CAD are FreeCAD and
BRL-CAD, but I'm not sure either would meet your particular requirements. I'm
pretty sure BRL-CAD doesn't offer the sort of parametrics you'd want (the
closest thing would probably be writing a procedural generator, which usually
means C/C++ or a scripting language). I'm less sure about FreeCAD - they use
the OpenCASCADE engine - but if the other commercial systems didn't offer what
you want I'd be surprised if FreeCAD had it (not impossible though - it might
be worth asking the dev team if your workflow could be realized in FreeCAD.)

Providing the STEP and STL files should cover pretty much what the open source
CAD world is prepared to handle - FreeCAD can import STEP and BRL-CAD is
working on it, and most 3D printing applications I know of can work with STL
just fine. Thank you for taking the trouble to make the extra formats
available.

