Question for Robotic Arm guru's........

[jaxnorth]

I am looking at building a gantry style foam mill. I want to be able to run 4 axis so that I can make things in 3D like column with intricate designs, and vases as well. However, I have seen these robotic arms on ebay and often wondered if it would be PRACTICAL to use one with a turntable mounted in front of it to rotate the foam block and use the are to hold a motor and spindle and carve away with it.

What is the concensus, would this type of machine using a 6 degree robot and a turntable work? What about programing the arm to create things in 3D? Luckily a gantry mill for foam carving is not to difficult, but with the prices the way the are for robotic arms, it seems like a lot of engineering could be bypassed by a good ebay purchase.

Open to any suggestions, thanks in advance.

[Evodyne]

jaxnorth,

Hi! Given a good enough deal on a working arm, it could be worth a try. I think I'd think about the following stuff (in no particular order)...

1. Is the arm interfacable to a PC so I can control it? If not, can I realistically hack it?
2. Is it going to be able to move and meet the tolerances for what I want to make?
3. Is it powerful enough to handle the milling end effector I want to use (spindle,router, etc)?
4. Can I find CNC software that works in spherical or cylindrical coordinates?
5. Will it fit into the space I have, even as the arm moves through it travel extremes?

If I could answer YES to the above and the price was right (including shipping), then I'd go for it.

Evodyne

[keithorr]

Heroin is cheaper. Hitting yourself in the head with a hammer is more fun.

[jaxnorth]

Thanks for the tips.....I have not found an arm that could be hooked up to a PC yet, althought I wondered if I could use a controller that did work with a PC to hook directly to the axis and make it work that way. I was hoping since it would be working with foam that the arm would have enough close tolerance and torque to run. I bit more research is definately in order.......

[wjbzone]

Here is a good starter robotic arm:

http://www.govdeals.com/eas/itmDispl...2617&acctID=63

Bill

[Evodyne]

Here is a good starter robotic arm:

Good Lord! And the bidding starts at 50.00? No wonder-it would cost a small fortune to move 'em.

[jaxnorth]

yeah...but if you could make em' work....what a pair of machines.........

[whiteriver]

Stay away from the fanuc robots. I bought one and there all 3 phase. Even the servos and drives are 3 phase. Would be a nightmare. I sold mine.

Donny

[JPMach]

I saw at a recent tool show a robotic arm with a router spindle on it and a tool rack and laser tool measure. I think it was at delcam's booth but I can't be sure. They said it would work for foam and wood and light cuts in alum. I too was thinking about building a 5 axis gantry style router, but I am intrigued with the possibilities of using a robitc arm. The demo the gave the work was mounted at an angle and everything. The only thing I question, is ( and maybe they weren't running it at full speed)how fast can you move these things ( what they were running seemed like around 100 ipm wich in al regards is slow.
If it would work I could easily see a robotic arm mounted to a linear track, just think of the possibilites!

JP

[Evodyne]

I saw at a recent tool show a robotic arm with a router spindle on it and a tool rack and laser tool measure. I think it was at delcam's booth but I can't be sure. They said it would work for foam and wood and light cuts in alum. I too was thinking about building a 5 axis gantry style router, but I am intrigued with the possibilities of using a robitc arm. The demo the gave the work was mounted at an angle and everything. The only thing I question, is ( and maybe they weren't running it at full speed)how fast can you move these things ( what they were running seemed like around 100 ipm wich in al regards is slow.
If it would work I could easily see a robotic arm mounted to a linear track, just think of the possibilites!

JP

There is nothing inherently difficult about an arm; if you can build a 3-axis router ou could probably handle an arm. Two problems I see though: first is mechanical-each joint has to handle the weight of everything downstream of it. The arm acts like a log pole with a weight attached-it will tend to wobble or oscillate. So it would need to be well thought out to get the accuraies you want. Second: software-robots, because of the pivoting joints, don't use cartesian (x,y,z) coordiantes, but rather cylindrical or spherical coordinates. If your software can handle that fine, if not, oops!

Lance

[unterhaus]

A decent sized arm is pretty dangerous. It's far more dangerous than a gantry router.

On the other hand, a lot of industrial robots are going for scrap prices. They are allmost all going to be three phase, and lots of it. I think mine took 60 Amps at 230V three phase. That's why it's now in pieces.

[DrStein99]

I bought an abandond arm-robot project from ebay for about $25. I have taken over the project and completed it mechanically, under two axis so far - to operate.

It's two rails are about 19" long each. It has another rail at the end with a gear, that isn't hooked up.

You can see me operate it here, the demo video clip is on the page (be patient to download):

http://www.raidgear.net/RND.aspx

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Having trouble trying to figure out how to attach the third rail (or third axis). The first two have pulley gears at the base, the first one operates the entire arm, and the 2nd one runs belts thru the rail onto the first elbo. This makes it so when I rotate the first axis - the 2nd axis remains at the same position.

This stuff is all new to me, so if anyone has advice, or links on building arm-robots, I would appreciate it - thanks.