Re: [CAD_CAM_EDM_DRO] degrees of freedom Was: Angle Iron Ways

Look closer... If you have 'fixed' length struts (I mean really fixed, not
extensible or retractible) the platform cannot move. On a hexapod, at least
two adjacent struts must be extensible to have even one degree of freedom.
four adjacent extensible struts should allow you 3 degrees of freedom, and
all 6 struts movable should give you your 6 degrees of freedom. ...Unless
my observations are greatly in error...

RayHex

-----Original Message-----
From: Dennis Schmitz <denschmitz@...>
To: CAD_CAM_EDM_DRO@yahoogroups.com <CAD_CAM_EDM_DRO@yahoogroups.com>
Date: Friday, August 18, 2006 9:52 PM
Subject: [CAD_CAM_EDM_DRO] degrees of freedom Was: Angle Iron Ways

>I was reading the description of hand tooling a precision flat and was
>trying to figure out what he meant by "kinematic" since it could be
>lots of different things, and one of my google searches lead here:
>
>http://www.hexel.com/
>http://www.prsco.com/rotopod.html
>
>Call me sheltered, but I've never seen a positioning stage anything
>like this. I've seen these things (which I now know are called
>"stewart platforms" or "hexapods") in optics labs, but never on a
>machine tool. But then again that shouldn't be too surprising because
>I design high performance processors and systems for in my day job
>rather than CNC machines.
>
>What's neat about this one is that there aren't any hydraulic
>cylinders or otherwise complicated mechanical strut actuators, but
>simple fixed length struts. And what look to be very expensive ball
>joint bearings, but I don't think they're really necessary.
>
>Then I looked around some more and found this router. It looks like a
>giant robotic spider took over his shop, but in a cool way. The lead
>screws are enormous.
>
>http://www.foxkid.net/cmm/platform/project-notebook.html
>
>You obviously don't need REALLY need a 6-deg freedom system for a
>router, but it might come in handy if you needed to carve a couple
>dozen wooden indians or something.

<snip>