Encasing Magnets to prevent demagnetizing. Glue?

[lnlogauge]

I'm working on a project, that requires magnets attached to the side of an aluminum casting, with the potential of 160kA pulling through the casting. Not being too familiar with magnets, we tested the assembly with an AlNiCo horseshoe magnet at 75kA. I bet you can guess that outcome.

Since then, we've moved on to NdFeB, and possibly SmCo magnets. I'm thinking I will use a similar horseshoe shape, with the 2 magnets encased in a low carbon steel rod. Does anyone have experience with the thickness I need to use to encase the magnet? I'll start with a 1/2 dia x 1 magnetic rod. Also, what kind of adhesive do you recommend keeping the magnet in the steel?

 

[sreid]

You'll need to provide much more information about what you are trying to do. RE magnets are much more difficult to demagnetize than AlNiCo. Encasing magnets in steel can keep external fields out but will also keep the magnet's field in.

 

[MagMike]

As far as the adhesive is concerned, the magnet is just another piece of metal. Choose any that'll meet your specifications but keep in mind that thermally cured epoxies might weaken/demagnetize the NdFeB during the heating cycle. Experiment before going to full production.

 

[lnlogauge]

I'm only encasing the magnet on 3 sides. I'm going to build the assembly below, and do some testing. I've heard that by recessing the magnet, you can narrow the magnetic field. On the assembly below, the top piece rotates around. I want the bottom to be pulled up only when the top piece is completely level.

 

[lnlogauge]

what would be the best way to map out the forces of this magnet? I was looking into buy an EMF meter, but not sure that's going to give me the precision I need. I also grew tired of reading ghost EMF meters.

 

[BrianE22]

It might be worth while for you to buy a 2d magnetics program. Quickfield offers a student version. I believe the are some other free ones. You can then get a plot of the magnetic field lines.

 

[lnlogauge]

Thanks for the reply. I have Solidworks EMS, but it's not working I want it to so far. I'm only a few hours into it, but the magnetic field its showing me isnt even close to real world. I'll take a look at quickfield

 

[MagBen]

hard to catch what you are asking, people can hardly help you out. what is 160KA? pulling force (wrong unit)? are you trying to pull the steel rod? in the images what are magnets, what are steel parts?

The pulling force is strongly related to the distance betrween magnets and steel. horseshoe shape doesnot matter as long as you are forming a close circuit.

if red ones are magnets, top plate is steel, 2D software will get you nowhere. Thinking about how the magnetic flux flows will help you to mkae an ideal design.

 

[lnlogauge]

Its going along a high voltage switch. the 160kA is the amperage that the switch is rated for, for 10 cycles at 60hz.

The design I currently have is replacing the horsehoe magnets with the design above. On the top I would have the left magnets in N, and the right magnets in S. the magnets below would swap. The plate in between is aluminum, its just a plate for the magnet to rest against when its pulled up by the top assembly.

Right now, the magnets are pulling too early, because our the field is too wide at the pickup point. I need a way to narrow the field significantly, without losing any strength at the middle of the field.

 

[MagBen]

It seems to me you wanted a strong magnetic field and the field needed to be foucs. I donot fully understand your design, but maybe in some point, the magnets cancel out yielding a wide range of flux density. My recommendation is, to simplify your design, you may try only one magnet with two steel pole pieces to mimic the horeshoe for a close circuit with your top plate. You will be almost impossible to get a horseshoe rare earth magnet. The horseshoe AlniCo is to increase L/D ratio for improved demagnetizing, and to form a close circuit with a pole piece for a highest pull force. A RE magnet is much stronger than AlNiCo, and also, much more capable to against demag effect, so you may not need to have multiple RE magnets to form a so-called horeshoe structure.