Re: [CAD_CAM_EDM_DRO] Re: RoboFac / Stewart-Gough Platform / Hexapod Milling Machine

Jeff Goldberg wrote:

>[...]
>
>I don't think I am talking out of turn by saying that the number of moving
>parts and joints in a tool, as well as the length of unsupported linear
>mechanisms and the accumulated backlash are all going to play a part in the
>overall accuracy of a tool. A hexapod, for example, seems to exhibit a
>challenge on all of these parameters. While the control (software and
>hardware) seems to be what we all tend to look at, the mechanical design
>seems to take a back seat. While we, as hobbyists, are on occasion, willing
>to make compromises based on budget or ability to create professional
>versions of what we envision, we should be aware of the consequences of our
>decisions and a discussion of what constitutes a rigid design is not a bad
>idea.
>
>Jeff
>
>

I have some ideas on how to reduce rigidity and play if I get around to
building a RoboFac Mark II.

RoboFac's number one rigidity problem is in the linear actuators. They
have to be able to move smoothly, the insides of the plumbing pipe I use
is not smooth. Therefore, I have to compromise and make the guide for
the screw inside the pipe a little small. This causes some play in the
actuators perpendicular to the long axis.

I've tried to skirt around the rigidity issue so far by taking light
cuts. For hobbyists, I think this is fine.