[j_cso]

If I add a range extender axes to a UR robot, all the axes move together as expected.  But if I run the UR posts, they say >6 axes aren't supported.  

I see that there are posts like the _sync post that will have multiple robots wait for each other so that they start each motion command together.

But I'm wondering how it's supposed to work when the arm and external axes need to move together to execute a MOVEL.

I'm guessing that some robots have built in support for external axes, so you can hand everything to the robot and let its IK handle controlling the external axes as well as its own.  (And then hope that the robot's IK matches what your simulator expected).

But for robots like UR that don't support that, how would I get my extender to follow the (potentially quite complex) path to get a MOVEL while the arm is following its path (which, it occurs to me, probably is also more complicated than a MOVEL since only the coordinated motion actually produces a linear move)?

[Albert]

You can try generating your programs with the Universal Robots Conveyor post processor. This post processor uses the set_conveyor_tick_count to drive an extenal axis (first synchronized external axis).

It is better if you contact us by email so we can better help you customize your post processor to drive additional axes for Universal Robots.