InMoov Finger Servo Pulley

by MdG_NL Oct 4, 2015
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hello, how to strengthen the second fishing line (white on the video)

Ah yeh, it's hard to see...
This line (elastic) is clamped under the servo and pinned at the left side.

Hi Marten
The parts look extreamly well crafted - what design software are you using?
I have tried to round the hole entries for the tendons (in my changed wrist design for the self levelling hand) with the openscad minkowski - but that takes ages to render and - as it is additive - it's a bit hard to redefine the objects to get the wanted result.
Using a hot iron to round the entries looks like a big time safer!
I assume doing a lot of movements the tendons will dig their own channels and it will add friction.
As you should have your new servos soon in place I am looking forward to seeing your new results soon.
And you might want to replace the spring with a pressure sensor and adjusted software to command the fingers to press with a defined strenght?

Hi Juerg,

I'm using Vectorworks 2014, it has enough 3D futures.

About all friction things, I will see this hopefully this weekend where the most friction is happen.
It's still my first hand :-)
First I need to redraw the ServoBed for the smaller servo's.
I hope to finish and print it this evening, so I can mount all things together tomorrow during the day
This ServoBed is a simple version, without any sensor parts...
For the sensor ServoBed, I need more time to get a nice setup.

In my case, I think I will keep the spring when I get the sensors included.
If the sensor fails, there is still a servo safer (the spring) :-)
And it's not in the way...

Hi Marten
Did you also try to have the pulley doubled up with a closing pulley with a smaller diameter as Mats invented but with your improved shape?
Might be worth a try.

there is also a material called igus which should reduce friction. maybe print the tendon channels with a 2 extruder printer with this material for the channels?
maybe also use the servos kind of round ended messing tubes for using the screws with the buffers to avoid sharp turns on the tensions?

Hi Juerg,

I think the tendon channels are fine, these are printed in the length which gives less friction.
About your idea with the messing tubes could be nice.
Did you test this with your hands and do they fit easy ?

A other option is to heat up a metal peace (not to hot) which has the correct rounded form...
Hold in on place by each hole for a second.
This gives (I think) a nice round and "blurry edge" result without extra weight.

Have you seen the new pulley's ?

InMoov Finger Starter (including a servo-safer option)
by MdG_NL

Hi Juerg,

Thanks for your comment!
In my new design I will include Mats option.
It's a easy thing to include this, so why not give it a try :-)
This new pulley will be soon uploaded here @ ThingiVerse.

Hi Marten,

thanks for sharing your pulley design. I try to understand and use it. However I'm not sure how to connect the different lines to the pulley. For the black one in the video (the one bending the finger) it seems quite obvious. But I can't figure out how to connect the white one (the one stretching the fingers). In the video it seem to run on a "fixed radius" compared to the black one. Any chance that you share some more details. And by the way, have you already finished the pulleys for the other fingers. Would be perfect if you could also upload.


Hello Michael,

Sorry for my late reply.

I will come back later with some more details, how all things are connected.

The white line is a elastic cord !
It's just strong enough to pull the finger back to the open position.
I'm still testing some other configurations, with a spring instead of the elastic cord.

And no, I haven't finished the pulleys for all other fingers :-(
But with the new spring configuration, it's no matter about the exact size of the pulley :-)

I hope to finish this soon in a successful finger / servo configuration.