Mechanics and Construction > Mechanics and Construction

Need Help Spec-ing Robot Arm

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awilson:
I need a robotic arm capable of picking up a part weighing less than 16oz. from a tray no bigger then a sheet of paper (8.5” x 11”).  The arm will need to move the part through a plane on the opposite side of the tray, but no farther from the base.  Estimating here, but I don’t believe the arm will ever need to fully extend.

Time is more critical then price (to a degree), so I thought my best bet would be to purchase a higher quality robotic arm kit.  This way the robot can be constructed faster and the learning curve for programming “should” be less.

My question to anyone gracious enough to check is, do you think the CrustCrawler SG6-UT
http://www.crustcrawler.com/products/arm6.php?prod=11 would be suitable?

From what I can gather, the lifting capacity should be adequate and the reach is there.

Thanks.

First time robot builder (assembler)
awilson

Some calculations to show the crustcrawler arm cant do what you want . . .

The crustcrawler robot arm base servo can lift 343 inch ounces.

Looking at the arm, based on given weight and length, and an estimated center of mass at 1/2 distance (probably more), it would require at least
2.34 lbs * 16 oz/lbs * (17.2"/2) = 321 inch ounces
just to lift its own weight . . .

So at full arm extension, the arm can lift and additional 343 in-oz - 321 in-oz = 22 inch ounces.

Now if you put a 16 oz item on the end of the arm, that would require 16 oz * 17.2 inches = 275.2 inch ounces.
Thats ~250 in-oz more than the arm could ever handle!!!

So the reason why their robot arm claims to lift so much is that the rating is NOT at full extension ("max lift capability" just means how much it can lift, not at what distance). If the robot arm was retracted half way, the torque required would also be halved (since the distance is half). Theoritically, the arm can lift its maximum amount when it is completely vertical because the moment arm distance is near zero.

Depending on motions that you require, an X-Y table robot arm might be more suitable for you.

awilson:
I can get away with changing the requirements to lift a max of 3oz.  But I still need a robot to do this.  Can you think of any other easy to use (quick startup) robot kits that could handle this beside the crustcrawler and the lynx.

awilson

P.S.  Sorry, I did post in a couple of places.  As a newcomer I didn't want to anger anybody for posting a question in a unrelated area.

more hobby like robot arms:

http://www.pololu.com/products/joinmax/0097/

http://www.pololu.com/products/elenco/0325/

http://www.hobbytron.com/product634.html

affordable professional robot arms:

http://www.strobotics.com/r17.htm

http://www.strobotics.com/r15.htm

http://www.strobotics.com/r19.htm