constraints and modelling a hinge


I’m trying to model a robot-arm (i.e. a thing with hinges). I want to constrain the joints to rotate about just one axis. Can anyone advise me on how to set this up in blender using some combination of constraints / parenting.

I’ve seen all the tutorial on mechanical modelling but I’m still stuck…

How-ever I try to set this up, I can (and therefor do, intentionally or not) always rotate the joints in an un-physical way (i.e. not just about the specified rotation axis for that joint/hinge). The Track-To and Lock-Track constraints seem to define the object orientation absolutely and do not allow any freedom of rotation about the joint-axis.

Any help would be much appreciated.

is each part an object, or is the robot rigged with armatures?

if the former (objects) you will just have to animate by rotating around the local axis, not the global one.

if the latter, I am not sure

either way, constraints will not really help you, unless you are doing IK with an armature and somehow find a way to specify exactly the IK plane

I’ve experimented with both methods (parenting eachjoint object to respective bones of an armature, and using a single object with full armature).

I’ve not yet got into the habit of using local view modes. It sounds like this would make things easier.

Thanks for the comments.