I set myself a task to create a single 3D printed hand with an "Opposable" thumb.
If you would like to build this then check my Video here first, it will run you through the basic build .....
Full Build instructions :-
The design I present here comes from some of my previous jointed finger experiments.
First version (blue one) was made with normal PLA just for a feel of the concept.
Second version was made with Flexible PLA and I would advise this for full flexibility, for best results choose a low Z axis increment ie 0.1 mm ... this will give the base part may cross layed layers to help with strength and durability.
Also with 0.1mm the cable tubes are stronger.
If you are using flexible PLA then i also suggest you use 100% infill as this also helps strengthen the cable tubes.
Basic hand has a backplane , the flexible_ish part.
The cable/ligament trunking runs hide the cables.
The cable ductings carry the Fishing Gut from wrist to finger tips/opposable thumb and knuckles.
I used a flatbed scanner to freeze my hand in time and imported it into blender "Images as Planes"
(just remember to activate this command under user preferences.....then be sure to select the texture button so the image appears)
Its then an easy job to use the Bezier curve tool to plot points around the outline of the hand.
The Curve was then converted to a mesh and extruded along the Z axis - and this was the basis of its creation.
The cable runs were done almost the same way ....
Yes the normal PLA version worked however it had limited movement....so... I designed a second version for flexible PLA.
Cables were threaded through the ductings and secured at the fingertips,opposable thumb and knuckles.
...and a few test hand positions proved its concept.
To help with the springback of the fingers after activation I coated on the back thin tracks of elastic silicon sealant,
this worked wonders and gave a good realistic action.