Rotary conveyor tracking question IRB 120

Chitty · Apr 30, 2012

I am looking at buying an ABB IRB 120 robot, I am needing it to be able to pick a small part off of a tray with pockets in it to locate the part, then put it into a revolving rotary table that does not stop that had 5 collet chucks on it. The chucks are on the same bolt hole circle, but not exactly the same spacing apart,(rough casting/only clearance holes on collet chucks) The robot has to hit the collet chuck with a clearance of +-.005 from collet to part. Is this possible? An encoder would be used for registering the table speed. The robot has a repeatability of .001" but when adding the conveyor tracking does it loose that tolerance?

Ox · Apr 30, 2012

Read through this thread:

http://www.practicalmachinist.com/vb/cnc-machining/need-someone-look-over-path-calculation-237498/

You would be adding a radius to the equassion as well.

However - I wonder if you could run in ABSOLUTE and continually follow the table as opposed to catching the spot with a prox as in the conveyor app?

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matt_isserstedt · May 1, 2012

I don't think that's a good idea...think about if you have anything which stops robot motion or the robot's program (Estop, fail to close gripper, etc) you stop the robot in the path of the rotating table...crash.

Not to say its impossible but can you build a simple indexing mechanism that locates on a series of hard stops. It could also be Camco-type (Ferguson also makes them) boxes are impressively repeatable but spendy as well.

Could also be a servo rotab so you can hit positions reliably.

Another tactic, place the parts into a tube with an escapement mechanism at the bottom, position over the nest in the rotab. Then use timing to hit the nest, then you'd need some sort of clamping crowding to make it reliable in the nest to your .005"....sounds like a PITA....

Chitty · May 1, 2012

Ox

Yup! that is what i am trying to do, but adding rotation. just wondering if the robot can keep the positions of 5 chucks within the tolerance i need.

this machine is up and running manually, parts are .080" thick .5" dia. only gets held by.020" in collet

Basically its a manual mill with a motorized rotary table on the bed. parts get loaded into collet chucks, collet closes, face mill removes .050" in one pass, keeps rotating collet opens, and shop vac picks part out of collet and is ready for another part. We have machined 500 000 of these pc's so far and would like to automate it. Robot is going to load and unload these pc. at 900pc's per hr.

Wishful thinking? or possible? table needs to keep moving to keep up with parts per hr required.

motion guru · May 1, 2012

Unless the Robot has a built in kinematic function for a dynamic rotary table . . . forget about it.

I have seen this done with Delta Robots - typically using an open controller like a Delta Tau or Siemens Simotion. I have also seen robots retrofitted with 3rd party controls that have been programmed to do this - but I have not seen an OEM robot manufacturer provide this functionality out of the box - doesn't mean it hasn't been done, but usually I get companies contacting us to do this kind of thing and it is never cheap.

Mini Delta Robot with background noise to verify actual speed - YouTube

Tonytn36 · May 1, 2012

Don't know about other mfg's, but Kawasaki offers an encoder input option on the robot. The robot motion can be tied to the encoder as basically a 7th axis rotary unit. This is used for several things (rotary welding and conveyor tracking, just to name a couple.) Sounds like you only need an RS03N for what you are doing. If you need the precision, which you do, this is the way to go. We've had one such system running since 2004 tracking a conveyor, no issues with it.

Chitty · May 6, 2012

Just found out from ABB rep, that robot is accurate to .01mm, repeatability to .02mm add conveyor tracking it jumps to +- 2mm when tracking at 150 mm/sec, this is not gonna work for my application, Damm, thought i had this one figured.

Ox · May 6, 2012

Chitty said:
Just found out from ABB rep, that robot is accurate to .02mm, repeatability to .01mm add conveyor tracking it jumps to +- 2mm when tracking at 150 mm/sec, this is not gonna work for my application, Damm, thought i had this one figured.

Fixed it for yuh. :Yawn:

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I am Ox and I approve this h'yah post!

Chitty · May 7, 2012

Thanks Ox, still won't work! :cool:

Ox · May 7, 2012

...yeah .... well ... (shrug)

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I am Ox and I approve thie h'yah post!

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