Electromagnetic interference—or EMI—is ever-present in our day-to-day lives. It is everywhere and it’s impossible to completely avoid. EMI is known to come from places we may never expect, including the sun in the sky and the ground beneath our feet. Too much interference can cause electronic systems to malfunction. This is somewhat ironic considering the systems themselves produce a magnetic field, and therefore magnetic interference.
The solution? Magnetic shielding.
Creating a magnetic shield, though, requires skill. But making the right magnetic shield requires extensive knowledge and expertise.
So, how do we do it?
Understanding Magnetic Shielding
Let’s take a moment to understand how magnetic fields work. Magnetic materials, by their nature, create magnetic fields. Likewise, electrical flow also creates magnetic fields. When magnetic fields move, they create an electrical current. The electrical current is the source of electromagnetic interference.
When we say “EMI is ever-present,” we mean it. Not only is it a naturally occurring phenomenon, but powerlines, computers, and cell phones also create magnetic fields and electromagnetic interference.
While electromagnetic interference does cause, well, interference, it is not typically a problem. However, as our devices and systems shrink in size and grow in capability, they become more vulnerable.
The right magnetic shield will deflect and reroute magnetic interference around the system inside, preventing malfunction.
How to Make a Magnetic Shield
When creating a magnetic shield, all factors must be taken into consideration. If the system is going to be submerged in the ocean, its shield will need to be constructed differently than if it will be going into space. So, for the purposes of this article, let’s discuss how to make a magnetic shield in the broad strokes.
1. Material Selection
The key property to be aware of when it comes to creating a magnetic shield is ferromagnetism.
Ferromagnetism is the tendency of certain metals to exhibit strong magnetic properties.
The most common metals used in magnetic shielding are:
- Iron
- Nickel
- Iron-Nickel alloys
- Copper
- Aluminum
Each of these metals will absorb and reroute EMI, keeping the device within the shield safe from the interference. This property is known as magnetic permeability.
Choosing the right metal is the first step to a successful magnetic shield
Because different metals can handle differing amounts of EMI, it’s important to select the right material for your shield early in the process.
For example, aluminum is not as effective as iron-nickel alloys, but it is much lighter. So, aluminum is great for aerospace applications, but the iron-nickel alloy would be better suited for medical devices.
2. Design and Prototyping
Now, if you’re unsure how much shielding you need, you may need to prototype different shields before you lock in which metal. And that’s totally fine! It’s better to find out what doesn’t work early in the process before you’ve invested a lot of time and money into research and development.
When prototyping and designing the shield, there are a few things to consider:
Determine Material Thickness
The shield’s thickness is critical. Determining the right thickness depends on the size and nature of the magnetic field, what you’re shielding it from, and the shape of the shield.
A shield that is too thin will become saturated, but a shield that is too thick can become too heavy for its designed application.
But there are creative ways around the problem. Recall how aluminum is not the most effective shield? When the metal becomes saturated, magnetic flux will start traveling through the wrong side of the shield. But what if you had another, smaller shield inside the bigger one? Now, you have an extra layer of protection for the device within the shield.
Having a team of engineers will help identify and work within the factors that affect the shield’s effectiveness.
Increase Distance
Another solution is to adjust the distance between the magnetic shield and the device you want to protect.
Magnetic fields become weaker the further they need to travel, so increasing the distance between the field and the device is another option to consider in your design.
3. Cutting, Shaping and Forming, and Heat Treatment
Now that you’ve identified the right metal and design for your shield, it’s time to head out to the shop floor and take the project into the real world!
Cutting
First, you take the sheet metal to the cutter. Precision is key here, as the initial cut forms the basis for the final product.
There are several cutting methods, such as laser cutting, that are both precise and powerful enough to cut different types of metals without compromising their properties. What are you looking for? Clean cuts, minimal waste, and flexibility in creating potentially complex shapes and designs.
Shaping
After cutting, the next step is to start making that sheet of metal look like a shield. We call this process shaping.
Shaping is the initial process of bending and manipulating the metal into the needed specifications for the shield. This can be achieved through techniques like press brake forming, where the metal is placed between a punch and a die to create bends.
Shaping is crucial for achieving the correct contours and angles for the shield to effectively deflect electromagnetic interference.
Both shaping and forming are important steps for creating the end result.
Forming
Next is forming. If shaping is about creating the initial shield, forming takes that outline and finalizes it.
This is done with additional bending, stretching, and compressing to refine the shield’s structure. In situations where more complex geometry is involved, more advanced techniques like deep drawing and spinning can also be used.
This step is essential for creating a perfectly shaped shield.
Heat Treatment
There are several types of heat treatment processes and subcategories of each. Just a few of these processes include annealing, normalizing, tempering, and hardening.
Each heat treatment process will achieve different outcomes, but that’s actually why it’s an important step. The goal of each process is to reorganize the metal’s atoms to make the metal do what we need it to do at a microstructural level.
For example, annealing processes make metals softer and stretchier—which we call ductility.
The normalizing process also makes metals softer and more ductile, but slightly less so than annealing.
Sometimes it’s appropriate to combine processes to yield different results. For example, we can anneal the metal to maximize its softness and ductility and normalize it later, knowing it will become harder and more durable. We explain how that works in this blog.
4. Welding
Now that the shape is finalized, it’s time to lock it in. The welding process joins the edges together and reinforces any areas in need of it.
For magnetic shields, precise welding techniques are vital for the shield’s integrity against EMI. Techniques such as TIG (Tungsten Inert Gas) welding, spotwelding, gas welding, and submerged arc welding are all renowned for their precision, control, and the high-quality welds they produce.
5. Surface Finishing
To push the magnetic shield to the next level of performance and durability, surface finishing is crucial. For instance, it can help enhance corrosion resistance and improve surface conductivity.
Grinding is an important step for finalizing the shield’s design.
Specialty powder coatings can be applied—though they are not always necessary.
Nickel alloys are very common for magnetic shields, so let’s use them as an example:
- Alloys that are 80% nickel will not rust, so they do not need powder coating.
- Alloys that are 50% nickel will oxidize and develop a yellow tint. This won’t affect the shield’s performance, so applying a powder coat is purely an aesthetic choice.
6. Testing and Quality Assurance
After the magnetic shield has been crafted, it’s time to test it. This phase is designed to confirm the shield’s effectiveness, reliability, and regulatory compliance.
Tests include evaluating the shield’s effectiveness, structural integrity, and its resistance to environmental stresses.
Turn to Eagle Magnetic for Your Shielding Needs
Developing a magnetic shield is a complicated, time-consuming process. Even seemingly small errors along the way could lead to a shield that doesn’t perform the job it needs to do.
So, don’t leave anything to chance!
The team at Eagle Magnetic has been specializing in developing and creating magnetic shields since 1970. That means when you work with Eagle, you are working with an organization that has over 50 years of experience and expertise.
Remember, EMI is everywhere, so your systems and mechanisms need to be protected from it. When your projects need the right shield, they need Eagle Magnetic.
Contact us now to get started!
