Help With Magnet Gripper for Robot

[RobotWhisperer]

Hello all, and thanks for taking time out of your day to help me.

I have a very unique problem, where we have to pick up small metal screens with a robot. About the only way I can figure out how to do this would be to use a small magnetic gripper. Something similar to this:

http://www.schunk.com/schunk_files/attachments/EGM__Highlights__2013-04__EN.pdf

My worry is that these screens are stacked one on top of another in a tall stack. My limited knowledge of magnetism says that this will not work as the magnetism will 'bleed' off into the stack and it won't be strong enough to pick anything up, or it will pick up multiple screens and not just a single screen. I'm hoping you guys and gals say otherwise.

I also considered using an electromagnet with an adjustable input voltage to where I could dial it in and find a sweet spot where it would only pick up one screen at a time, but I don't know how reliable this would be.

Anyone have any ideas as to if this will work, or how to make it work?

 

[MagMike]

Can you use a sheet fanner first, to separate the screens?

Here is a link to an industrial unit:
Link

 

[IRstuff]

I'm really having a hard time imagining that you could get that precise a control on the magnet, to keep one, but drop a second one.

What do the screens look like? Could you do something with a vacuum approach?

TTFN
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[RobotWhisperer]

@MagMike

A fanner was my original idea, and we have used them with good success in the past on solid sheets. However, I had the company that we buy ours from take a look at this and they are very hesitant because the side of the screen is not a solid line of metal, but rather just little points of sharp metal where ever it happened to be sheared. This scares them, as they think we won't get a very reliable pickup. I might be forced to try it out anyways.

@IRstuff

I'm having a hard time believing that tight of a control can be kept also. The screens run anywhere from 9" to 12" square, the metal lattice is about 0.75 to 1.0 mm wide metal, with the gaps that it makes being about 7-8mm squares. So, just because of the size of those holes I imagine that a vacuum wouldn't quite do it.

Thanks for taking the time to reply though guys, I really appreciate the help.

 

[IRstuff]

Having no solid borders will make the fanning very difficult, since it's likely that whatever process delivered the screens into the stack will have bent some of the free ends, and they'll catch on the screen underneath.

Given the scenario described, I'd be tempted to suggest using gooey adhesive stuff to pick up the screen. I'm not really sure what it's called, but it's used for a variety of applications, including some sticky toys.

TTFN
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[mac2]

What is the screen made of? Round or square wire, expanded metal, etc...

 

[RobotWhisperer]

It is expanded metal.

 

[mac2]

What is the expanded metal thickness? Is each screen free from the one below it i.e. not tangled in any way. Is there an oil film between screens. Are subsequent screen openings in line with the ones above and below or are they randomly positioned? Do the screens lay flat? Depending on the answers to these questions, there may be a way to do this magnetically.