Re: RotoBot hexapod

>I'm thinking in terms of a benchtop machine with a fairly small
>work envelope.

Me too.

> There was a discussion, about a week ago, of how to make an
>antibacklash pinion

Someone also mentioned just spring loading the pinion against the
rack.

> Electrical connections could be done with rotating couplings --
>bushings or bearings, centrally located, would make easy connection
>points.

If conventional 5 axis milling was all that was to be performed then
I suspect you could just have he wires comming out of the top of the
central post. However the rotobot has the ability to do a good
impression of an upwards facing rotary table it it wants too. You
just send all the carriages around together and the table spins
around the central axis. I am assuming that with the right software
you could make it spin around any axis in fact. This is actually
better than a normal hexapod that can only manage a small degree of
rotation. Having said that they normally move the spindle so there
is not much point. So yes bushing, bearings or slip rings, but that
is a lot of them. 6*4 for steppers and more for servos.

>Unless I'm completely mistaken, it appears that the common balljoint
>at the platform end of the struts >is coplanar -- it functions
> as nothing more than a hinge between the struts, and not a 360
>degree

Only partly mistaken. It does function as a proper ball joint as
remember that although there is the hinge element because of the
coplanar nature of the stuts it still needs to hinge in other
directions to acheive movement of the table. i.e. the struts are
always coplanar but their plane it not always at the same angle to
the base.

> >If the machine is there, the software will follow.
> Yeah, but how quickly?

Well never without a machine. The CNC toolkit can be put to use to
produce 5-axis tool paths. TurboCNC could be modified for 5axis
jogging if required.

>(Especially > if there already exists an alternative) ;-)

Oh well, if there is one then that's another story.

Graham