gripper wrist assembly

[DrStein99]

I want to build a robot gripper wrist assembly; does anyone have any project links or resources for diy-designs? Please help, thanks.

[unterhaus]

You want just the wrist, or the gripper too? How much weight? Is it going to sit on a desk or be at the end of an arm? Most of the DIY grippers use hobby RC servos.

I need an arm like the one on the iRobot Packbot EOD. Unfortunately they cost more money than I have and iRobot isn't going to tell me how to program it anyway. I was just doing a search for parts, since I do have money. I'd love to build, but there is no way I'd get it done.

It's amazing what you'll find on ebay as far as robotics parts. Some of the older robots are pretty much selling for scrap. I bought a very large GE welding robot for $125. And there are a lot of pneumatic parts too, if that's and option.

[DrStein99]

I'm looking for a jaw-gripper style. I seen pic's here and there of some styles, but am missing different angles to give me ideas of how the mechanics work exactly.

Most of what I have seen the hobby-rc servo ones are made out of WOOD, and use rediculous thin metal to engauge the motion, or otherwise "hobby" mechanics (I assume) are intended to be safe for small children to learn.

The one I'm looking to build should have alot of clamping power, and jaws be about 3-4" apart (open).
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ebay is a good source for robot parts, I did buy a scrapped arm-robot project, all aluminum for about $20, that needs some finishing to work!

[unterhaus]

Not really defending them, but there are some pretty expensive arms that use hobby gearboxes. We have one that can definitely hurt you, maybe put you in the hospital. The gripper is fairly robust on that robot, it will hold a resonable amount of weight, but it's limited to golf ball sized objects. It's made out of plastic. There are heavy duty rc servos, so I wouldn't reject them out of hand. You can always make the gripper itself out of metal.

The gripper that Activmedia robotics makes for the pioneers basically is two jaws on a linear motion stage. The lead screw is right hand threaded on one side and left hand threaded on the other. As you actuate the gripper, they simply move together. This seems to be a pretty common design.

I suspect there are a lot of grippers based on the same principle as a scissors jack with a parallelogram on each leg so the jaws are parallel. And the rc servo version basically would be the same thing as the scissors jack variety, only they drive one of the arms directly with the servo. Although the jaws travel through an arc, that usually isn't a problem.

I don't know if that helps you, but it helped me

[DrStein99]

unterhaus;

Yes that helps alot. I'm looking at some designs with the lead-screws - but knowing the threads are setup like that solves alot of questions i was wondering!

And the more complex scissor jack design seems to have more torque and holding pressure - and definately alot of fun to watch activate!

I'll have a look into that activmedia stuff - thank you.

[unterhaus]

I was just looking at the powercube gripper, and a very simple realization hit me. It seems obvious that they use two leadscrews. http://www.powercube.de/files/PowerCube%20PG.pdf
I don't even want to think about how much that thing costs, I've heard that the powercube pivot costs $17000.

[trubleshtr]

what about a pneumatic over a spring type gripper?
I use alot of smc and schunk brand grippers. I may even have a few kicking around That I maybe persuaded to part with

[DrStein99]

Pneumatic spring gripper? Well. I need two. I'm building a tool changer.

Spaced about 2 - 1/4" apart, to grip a 1/2" rod.

I'm interested in knowing and seeing more on those smc grippers.

[greybeard]

Just a thought from an old lab. tech. - could you use/modify 'retort stand clamps' ?
One common design in the lab had a central right/left hand threaded rod at right angles to the axis of the gripper, with a simple knurled wheel in the middle driving the fingers outwards. Worm drive that and you have a powered gripper.

[DrStein99]

Thats a good idea. i didnt know what those things were called. I got some good pics here thank you!