Magnets in Die Cast Dies...Alnico 5 or 8? Limited space, inserted?

[wendorff]

We have an engine block die that requires sleeves be cast into the part. The problem is that the repeatability of the robot placing the sleeves on is not perfect and on occation, the sleeves are not fully "seated" on the core. To correct this we want to experiment with mangets placed on the bottom of the core. I have done quite a bit of research on mangets and found that I need an Alnico magnet.
My questions are...
1. Alnico 5 or Alnico 8? (I have limited space and cannot maintain a 5:1 length to diameter ratio).
2. Other than machining, do I benefit (more magnetic power) from inserting a magnet into an insert with detail or EDM the detail right onto the magnet?
Any assistance with this will be greatly appreciated!
Thank you.

 

[MagMike]

Hello Wendorff,

If you cannot maintain the long length ratio, Alnico 8 is the better choice. However, if there is some way to shield the magnet from the heat of the casting process, you'll get more power from a SmCo magnet. If the magnet will see less than 450degF, SmCo will still put out a lot of power.

Generally speaking, more magnet volume will produce more magnetic power, so I'd avoid using EDM to put any details into the magnet.

Good luck,
Mike