I have created an animation with the Rigid Body. It is a simulation of a robotic arm. It is a 3D printable arm that I arranged in Blender. It works well for the constraints that have all the same direction (the arm itself).

But I am not able to add a constraint for the rotation. The rotation direction of the "normal arm" constraints is in the X direction, and the bottom plate is supposed to rotate about the Z direction.

I need a way to link the X-direction constraints to the Z-rotation. I can animate the two servo driven arms and the arm moves correctly, but I can't use the rotation, the arms don't rotate and the thing gets broken.

Screenshot of robotarm with empties (constraints)

Any hints?

  • $\begingroup$ To be honest I'd just use normal rigging methods for a simple arm like that, maybe with an IK constraint, rather than Rigid body which I've never used. There are lots of YT tutorials on rigging robot arms online and a very detailed one on rigging an aircraft landing gear here. $\endgroup$
    – John Eason
    Commented May 12, 2023 at 10:18
  • $\begingroup$ I know the Inverse-Kinematic-thing when animating people and so, but am not sure if it is capable of animation of such a mechanical arm. I don't need an animation to move the "hand", i need an animation that follows the rotations of the two arms that are driven by servos in the printed version. $\endgroup$
    – Tutorius
    Commented May 12, 2023 at 10:31
  • $\begingroup$ may i ask why you want to use rigid body here? because as far as i could see you animate it anyway..."normally" you would let Blender do the physics and e.g. just animate a motor constraint to move parts.... $\endgroup$
    – Chris
    Commented May 12, 2023 at 13:55
  • $\begingroup$ und mein Kompliment....! Ich habe noch nie ein so sophisticated rigid body robot arm gesehen....!! $\endgroup$
    – Chris
    Commented May 12, 2023 at 14:34

1 Answer 1


ok, i don't know whether you want it that way, but here is an example how you could do the rotation via a motor:

  1. delete all keyframes and uncheck the animated checkboxes of all animated rigid bodies

  2. Add a motor constraint like this:

enter image description here enter image description here

then you can animate the target velocity (what i did)

  1. add another motor constraint here:

enter image description here

enter image description here


(all driven by simulation, nothing animated except the velocities of the motors)

enter image description here

i think i don't have to tell you that the direction of the constraint is very important - because you wouldn't have come so far if you didn't know that ;)

Viel Erfolg!!


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