Lynxmotion 3DoF arm - repeatability?


I’m looking for a lightweight 3DoF robot arm that can reach the entire upper hemisphere of a spherical shell with up to 40cm radius. This is intended for a small semi-professional vertical niche market. The application requires sub-millimeter repeatability.

I’ve been looking at Lynxmotion’s 3DoF arm - the 4-bar linkage design would be ideal for my purposes, especially since it looks like the upper arm bars could simply be mounted in reverse so as to reach the entire upper hemisphere (though no longer the floor).

Where I have doubts is whether this arm would be stiff and tight enough, especially laterally, to achieve the required repeatability. I’d appreciate if anyone with experience with this arm could help me with these questions:

  • what kind of repeatability is achievable with the Lynxmotion 3DoF?
  • how stiff is the arm laterally? is it prone to oscillations?
  • are there any impediments to mounting the lower arm reversed?

I would probably upgrade the servos to HTs to increase the duty cycle and/or tightness of control; the question is whether the quality of the mechanics would suffice to translate that into higher accuracy & repeatability?

Coming at this from another angle: does anyone have suggestions for more up-market (say, up to $2k) 4-bar linkage robot arms to look at? (The Dobot & derivatives won’t work as they cannot turn a full 360 degrees, and reversing the lower arm looks tricky there too.)

Thanks in advance for sharing any relevant experience!


Hi linoleo,

The Lynxmotion 3 DoF will not work for your application.
It’s not constructed for high accuracy and the backlash alone in the motor gears will give you some mm play at the end.

Regarding it’s envelope, it will not reach your 40cm as you can see in the dimensions section:

You mentioned Dobot, it would be a more “industrial” platform if you can “hack” it to your needs.

All the best,

1 Like

Thanks for the clarification, you’ve confirmed my suspicions. Looks like Dynamixel XM/XHs would fit my bill on the servo side, but I can’t seem to find suitable 4-bar hardware for them. :frowning:

1 Like