Re: [CAD_CAM_EDM_DRO] A "simple" Hexapod project

Yo Graham;

I've never built one, but a hexapod has a potential I've never seen anyone try
for. Have you considered a, "universal pantograph"?

This would entail two hexapod setups, one with linear encoders and a probe tip,
and another with servos/steppers, with the cutting tool on it. Size scaling
could be accomplished in software.

Just a thought.....

Bill

On Fri Jun 13 07:47:35 2003 Graham Stabler wrote:

>This is a tentative and probing post just to get an idea of the level
>of interest folks have in making Hexapods. They were mentioed a
>while back and I have seen a couple of designs on the web that have
>been built by amateurs, one using an inverted Stewart platform and a
>router and the other using cables. (Search for hexapod in the archive
>for the links).
>
>I'm actually quite new to CNC really but the dream has kept me amuzed
>for a while now and the reality is proving to be most enjoyable. (I
>just made some USEFULL parts in Delrin on my Proxxon). I am doing a
>4th axix for that but after seeing a homemade 5 axis taig I have got
>re-inspired and see another potential dream to persue.
>
>I don't have the skills, time or money to make a hexapod capable of
>machining metal but I am an aeromodeller and the ability to shape
>foam, plastic, wax and balsa in 5axis would certainly be of great use
>or at least great interest.
>
>What I propose is a simple Hexapod based on the ideas of the home
>router/engraver constructor rather than the THK and ballscrew set.
>
>Hexapods have 6 actuator legs and as they are legs all designs I see
>tend to be based on telescoping tubes. Personally I can't imagine
>building a very rigid actuator in this manner (i.e. I can't) and
>finding tubes with precision bores makes the task more difficult. I
>am thinking of making an actuator based on two silver steel or
>precision ground rods. At the end which would be pillow blocks
>including at one end a stepper motor mount and leadscrew bearing and
>at the other a largeish Delrin bushing. A simple Delrin carriage
>could ride up and down these rails pushing the actuator leg through
>the bush in the pillow block. The part of the leg that moves would
>then have three points of support. The leadscrew would reside within
>the hollow actuator leg and be supported by a derin rider that could
>be a loosish fit in the tube. To stiffen the whole thing up plates
>could be added covering the assembly and locking the pillow blocks to
>prevent twisting.
>
>The leadscrew could be cheapo 6mm threaded rod and the nut a long
>nylon job these seem to be pretty good on the backlash and cheap to
>replace.
>
>Pivots for the ends of the actuators might be off the shelf ball
>joints of some kind or maybe gimble types.
>
>I am just wondering if anyone else might be tempted, and if my ideas
>are stupid. I suspect if a group of people had a go issues such as
>software and tricky hardware prolems could be ironed out more
>easily. Perhaps just start by making one actuator as I intend to.
>
>Off to Dream,
>
>Graham


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