How are spherical rare-earth magnets manufactured?
A question came up the other day when playing with Buckyballs of how you manufacture spherical rare-earth magnets.
I'm surprised they could use that name, given the original Buckyball, but these Buckyballs are powerfully magnetic spheres with one side a North pole and the other a South pole which can be stuck together to make 2D and 3D structures. Sale has been restricted in many places because of people ingesting them and requiring emergency surgery.
I've found information on neodymium magnet production using a sintering process, but can't see how you could produce a perfect Ni/Cu plated sphere with this method as individually machining to a sphere would be excessively laborious and tumbling would be a non-starter because of the attraction between balls.
The sintering page wasn't the one I thought I was linking, but the one I've linked looks like it may have the answer in die-pressing or isostatic pressing in the aligning field of a solenoid. Is this how it's done for spherical magnets? (Polishing the coated spheres would still be a problem.)