RoboFac Details

[SimonArthur]

I've gotten some questions about my hexapod machine, so I thought I'd post some details here. I haven't done my first cuts with the machine yet, as I discovered that my original configuration was too flexible and had to go back and make some changes. I changed the legs to be much stronger and added thicker braces to the corners where the actuators attach. I also have threaded rod with turnbuckles to keep the whole frame under tension.

I've attached a couple photos to give you an idea of what the machine's like.

More details on the software:
http://robofac.sourceforge.net/

[jimbo]

Excellent, I have been interested in these types of machines. I have been collecting parts for a variation of this machine. I look forward to seeing your progress.

[Torsten]

Interesting seams like a very compact design of your pushrods.
The Frame looks messy, seams its not tall enough too.
May want to start the frame over again, use thicker tubing and build
in a triangular shape like a standard Hexapod would be much sturdier.
A friend with a welder would help.
Good effort so good Luck.

[Pythagoras]

It appears you will need to apply some of my theorum here.

Tell us more about how you plan to generate the gcode.

What will you use to drive this device?

Is the software worth downloading and going to the effort of using Linux?

What are the advantages of a hexapod ?

More details please.

[SimonArthur]

Torsten: The frame has changed a bit since the photo was taken. If I wanted to start over completely, I'd do it a little differently, but the way I'm going right now doesn't seem too bad. Once I actually start cutting with the router, I may change my mind.

Pythagoras: Yes, the RoboFac software uses the Pythagorean Theorem to calculate the lengths of the actuators. You can download the source code at
http://robofac.sourceforge.net/
and take a look at the file HexapodGeometry.java.

G-code will be generated through standard CAM programs or manually.

If by "drive", you're talking about the motor drives, they're Xylotex stepper drivers. They're located inside the red box that you see on the table in the photo.

Linux, to me, is no great effort. Of course, the RoboFac software runs on Windows (and maybe even Macintosh) now, it just doesn't talk to the parallel port. Perhaps one day the code for driving the parallel port on Windows will get written.

Hexapods have a variety of advantages, including being able to move on 6 axes. After Christmas, I'll post more details.

[SimonArthur]

I updated the screenshots on the website; the images and links were broken.
http://robofac.sourceforge.net/

[SimonArthur]

I thought I'd give a little more detail about why I chose a hexapod over other designs.

First of all, I get full 6-axis movement, as I mentioned earlier in this thread.

Second, I liked the notion that I could build this machine without having to make a lot of precision parts. I didn't have to start with an existing milling machine. No parts are precision cut or positioned other than the special plate I made with calibration points marked on it. The RoboFac software compensates for accuracy problems.

Third, I've made the machine with a minimal amount of specialized materials. Nearly all the mechanical parts come from Home Depot, Lowe's, MSC, or Metal Supermarkets (my local metal supplier).

[fyffe555]

What are you using for linear actuators?

[SimonArthur]

I made the actuators using Acme threaded rod, Acme hex nuts, and plumbing black pipe. I may try making my own Delrin nuts, as the current setup is somewhat complicated.

[HuFlungDung]

It would be interesting to see how you figure out how to avoid gouging the part. That's something useful about ordinary 3axis machining which I never thought about, its not to difficult to rise to clearance, but on a 6 axis part, where is the clearance plane? And moreover, can you safely get there from here?

[SimonArthur]

6 axis geometry can get very complicated. I'm still not sure how ordinary milling machines handle it, and if its desirable to replicate the same sort of behavior on a hexapod.

As I'm just starting out with CNC, I think I'll just try using RoboFac for ordinary
3 axis stuff for a while.

[SimonArthur]

I finally managed to cut something good with RoboFac. It's taken nearly two years of effort, off and on. Photos are forthcoming, and I hope to release a new version of the software in the next couple days.