OT: Magnet Issue

This one's not directly PLC related, but it is automation related. Perhaps someone has crossed this bridge before:

We have a line where we use 24 VDC electromagnets to grip the parts and move them hither and yon. The problem is, our magnets are holding so much residual magnetism that they don't always *drop* the part when they are turned off.

These are basic magnets, nothing fancy. We tried turning down the voltage with a rheostat, to induce less magnetisim, but if you go a little too far - drop parts prematurely. Too little, and the part hangs around like an unpleasant relative.

We're already fiddling with these things for every different part size (50 of them) and it's proving to be a pain in the ash.

Any suggestions on how to break the part from the magnet effectively?

Thanks!

TM

We had a similar conversation: http://www.plctalk.net/qanda/showthread.php?t=28462&highlight=magnet

In the old days I worked with scrap yard magnets. I think they had schemes that put resistors across the magnet when it was turned off. But I also seem to recall something about reverse polarity.

Are the magnets shown to be polarized? If not reverse the power to them and they will demagnetize the core. Of course, eventually you will get the same issue with the south pole.

Can the magnets be run with AC? They might have a spec for AC volts.

Thanks Ron, exactly what I was looking for