Re: Hexapod design drawings

Doug,

Thanks for the explanation, but do you know of a diagram or picture
that would help in understanding the connections and layout of the
joints you describe as A,B,C,D,E,F. I'm afraid I'm having difficulty
in fully understanding it.

Rab

> The socket universals that I purchased, have no backlash.
> And of course being designed for high torque (a hundred or
> more foot pounds of torque) they are up to the task (for a
> small machine).
>
> > Can you pre-load the axis on a hexapod design ?
>
> That is the basis for a hexapod's phenomenal rigidity at
> such a light weight!
>
> Of the six actuators, three are always in tension, acting
> against three in compression. Coming to a triangular
> mount point above, the pairs
>
> AB CD EF
>
>
> instead are paired differently at the bottom (tool platform):
>
> BC DE FA
>
>
> so if AC&E are in compression, and BD&F are in tension at
> the top, then each actuator under tension is matched with
> one under compression. So it is also at the bottom (ie
> B under tension is paired with C under compression, etc).
>
> Keeping this state of affairs of course is one of the
> constraints of the hexapod controller software, and
> hence very difficult.
>
> - - -
> Some of you are no doubt thinking that under great tool
> pressure, all of the members will be under compression.
> In fact (or should I say, I understand) that the whole
> structure would then relax (causing positioning error)
> when the compression is relieved.
>
> Instead, the tensions and compressions are pre-set to
> far overwhelm the tool pressures, and hence there is
> insignificant relaxing (dimensional change) when the tool
> pressure is relieved (helping maintain tolerances).
>
> Or so I am led to believe......
>
> Doug Fortune
> http://www.cncKITS.com