Re: [CAD_CAM_EDM_DRO] A "simple" Hexapod project

I'd be interested in theory, but my shop's a little short on practice at
the moment (low cash flow). But I'd definitely be interested in peering
over people's shoulders during the design phase.

Tom

On Fri, 13 Jun 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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