[Mieth1]

we do a dull nickel plating to our parts. have always use copper wire. would like to make and use racks. what metal are racks normally made of? Copper racks work, but we'd be wasting nickel. what the best process?

[Arkcon]

If you spoke to the plating bath company, they may suggest a type of plastic that's compatible with your parts and their bath.  If you do everything yourself, you may find trade references.  Or you can just try some dense plastic for bath resistance.  I suppose, one nickel has plated out on your copper wire, it can't plate out any more.  So maybe simply reuse?