# Neodymium magnet partial shielding

• Martin Quevedo
In summary, the conversation discusses a situation where two cylindrical magnets are axially aligned with opposite poles facing each other, with a HiperCo 50 metal in the middle. The goal is to have the net force on each magnet be zero by canceling the force of repulsion between the magnets and the force of attraction between the magnet and metal. The participants suggest testing the setup physically and provide resources for finding the necessary math and theory. They also discuss the potential effects of the thickness of the metal plate on the behavior of the magnets.
Martin Quevedo
Hi all distinguished members of this forum !

As my first post here I would like to open with a situation I have been struggling with
I have attached a simple diagram of my problem

I have 2 cylindrial N52 neodymium magnets axially aligned with each other with opposite poles facing each other.

in the middle of both magnets there is a HiperCo 50 metal

The idea is that the net force on each magnet is zero. That is, the force of repulsion between the magnets and the force of attraction between magnet and metal (hiperco alloy) cancel one another.

I will very much appreciate if someone can share some math that allows to calculate the thickness required on the hiperco metal to achieve Fa and Fr to cancel.

I have also attached BH graph of the hipeco alloy

best regards,
Martin

Why don't you just test it physically? It's a lot more fun :-)

This website might be what you need for looking up the maths and theory:
http://www.physicspages.com/index-electrodynamics/
http://www.physicspages.com/2013/07/16/diamagnetism/

Magnets are dielectric with centripetal and centrifugal forces. They will exert that typical sideways pushing-away from each other if too close, which can be tricky to calculate. Hopefully you can try and make your "hovercraft" float with a far enough distance between the two magnets ;-) I suspect you need find a sweet spot (making the distance a harmonic of the wavelength maybe?).

If the plate is much larger than the magnets's field size it might be difficult to keep it horizontal.
I'm sure you already have this covered, but you will need something else to keep the plate stable until the forces settle and there is no more movement to induce new imbalance. Perhaps a simple tensegrity structure that will not restrict movement too much but stop the plate (and magnets?) from flying off. Just google it (or youtube).

By the way there are a few "home-scientists" on youtube who have created very interesting videos showing what EM fields actually look like. This might help you to figure out if your calculations make sense.

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Martin Quevedo said:
I have 2 cylindrial N52 neodymium magnets axially aligned with each other with opposite poles facing each other.

in the middle of both magnets there is a HiperCo 50 metal

The idea is that the net force on each magnet is zero. That is, the force of repulsion between the magnets and the force of attraction between magnet and metal (hiperco alloy) cancel one another.
If the plate is thick enough not to saturate, I don't think much of the field from one magnet will affect the other magnet. So the magnets will both stick to the sheet.

If the sheet is very thin and can saturate, then I think the math gets pretty complicated, and you may just need to simulate the setup to get an idea of the behaviors.

A better way to do this, IMO, is to cut a hole in the sheet between the magnets to let some field through so the magnets can influence each other. Experiment with the diameter of the hole versus the magnet diameters and spacings to see if you can arrive at a stable configuration...

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mfb
Dear Karin,

Thank you very much for your response!

I am planning to do some tests on this particular situation
I also wanted to know some math on the matter because I needed to at least get an approximate of the thickness of the hiperco 50 material to place between the magnets.

All 3 components are fixed in space by mechanisms not shown in my picture.

berkeman said:
If the plate is thick enough not to saturate, I don't think much of the field from one magnet will affect the other magnet. So the magnets will both stick to the sheet.

If the sheet is very thin and can saturate, then I think the math gets pretty complicated, and you may just need to simulate the setup to get an idea of the behaviors.

A better way to do this, IMO, is to cut a hole in the sheet between the magnets to let some field through so the magnets can influence each other. Experiment with the diameter of the hole versus the magnet diameters and spacings to see if you can arrive at a stable configuration...

I was under the impression (wrong apparently) that a portion of magnetic field would go through depending on the thickness up to a saturation point. But according to what you described, it is a all or nothing situation. If no saturation accurs, all magnetic field will be re routed by the metal plate. and only if it saturates the remainng portion of the field would pass through.

I am correct in the interpretation of your explanation?Martin

It is not "all or nothing", but if the plate is thick, the influence of the magnets on each other will be very small.

mfb said:
It is not "all or nothing", but if the plate is thick, the influence of the magnets on each other will be very small.
I was doing some simulation with QuickField. I used the BH curved provided by the manufacturer to configure the behaviour of permeability of the metal plate.
In the simulation I was able to reduce the force to zero by varing the thickness of the plate. So, if the simulation is correct, this should mean that there is a portion of the field passing through the plate influencing the magnet on the other side.
This would prove what you are stating here, mfb.

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Karin Rodrigues said:
I sure will
I am working with the simulations but sometimes it is a bit hard to get the BH curve of the material
Regards,
Martin

Karin Rodrigues

## 1. What is a neodymium magnet partial shielding?

A neodymium magnet partial shielding is the process of using a material, such as steel or mu-metal, to partially block the magnetic field produced by a neodymium magnet. This results in a weaker, but more controlled magnetic field.

## 2. Why would someone use neodymium magnet partial shielding?

Neodymium magnets are extremely strong and can have a wide range of uses, such as in motors, generators, and speakers. However, in some applications, the strong magnetic field can interfere with other electronic devices or cause safety concerns. Partial shielding allows for more precise control of the magnetic field and can prevent interference.

## 3. How does neodymium magnet partial shielding work?

Partial shielding works by using a material with high magnetic permeability, such as steel or mu-metal, to redirect the magnetic field lines away from the area that needs to be shielded. This creates a path of low magnetic field strength, effectively shielding the area.

## 4. What are the benefits of using neodymium magnet partial shielding?

There are several benefits to using partial shielding for neodymium magnets. It can reduce the strength of the magnetic field, making it safer to handle and less likely to interfere with other devices. It can also help with precision and control in certain applications, such as in motors or sensors.

## 5. Are there any limitations to neodymium magnet partial shielding?

Partial shielding is not a perfect solution and has some limitations. It can only reduce the strength of the magnetic field, not eliminate it completely. The effectiveness of the shielding also depends on the strength and orientation of the magnet and the type of material used for shielding. Additionally, it may not be suitable for all applications, so it is important to consult a professional when considering partial shielding for neodymium magnets.

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