As a custom magnet supplier, customers ask about the pull force of magnets from time to time.
You may want to know what determines it, how to measure it, and how to maximize it for different applications.
This comprehensive guide will share with you everything we’ve learned about this essential topic.
Let’s dive in!
What is Magnetic Pull Force?
The pull force of a magnet, also known as magnetic force, is the strength with which it attracts ferromagnetic objects like iron and steel.
This force depends on several key factors:
- The strength and grade of the magnet itself
- The distance between the magnet and the attracted object
- The material, thickness, and surface conditions of the attracted object
- The size, shape, and orientation of the magnet
The interaction of these variables determines the ultimate holding power of a magnet in a given scenario.
Types of Magnets & Pull Force
Not all magnets are created equal when it comes to pull force.
Here are the main types, in order from strongest to weakest:
Neodymium (NdFeB)
These rare-earth magnets pack the highest strength for their size.
Different grades like N52 offer even more power.
Samarium Cobalt (SmCo)
Nearly as strong as neodymium but with better high temp performance.
They are ideal for challenging environments.
Alnico (AlNiCo)
Made from aluminum, nickel, and cobalt.
They have lower strength than rare-earth magnets but excellent stability and temperature resistance.
Ceramic/Ferrite
The most economical permanent magnets.
- They are not as strong as the others but great for lower force applications.
In addition to these permanent magnets, electromagnets can also generate very strong pull forces when powered.
The strength depends on the current and coil turns.
Measuring Magnet Pull Force
So how do we quantify the pull force of a magnet?
We can do it with the right tools and techniques! Here are the key components for accurate pull force testing:
- Pull force tester (mechanical or digital) to measure the kg or lb force
- Standardized test pieces (flat plates or steel spheres) for repeatable results
- Non-magnetic spacers to test with controlled air gaps
- Magnetic viewing film and polarity indicator for diagnostics
To get reliable data, it’s all about consistency.
That means:
- Using the same test pieces and equipment each time
- Pulling slowly at a perfect 90° angle
- Testing at the center of the magnet
- Taking the average of multiple pulls
- Controlling for temperature
With a quality test rig and disciplined methods, we can track a magnet’s strength over time with high accuracy.
Factors Affecting Pull Force
Beyond the core properties of the magnet, there are several external factors that can dramatically impact the measured pull force.
Air Gaps and Distance
Magnetic force drops off rapidly with distance.
- In fact, it decreases with the square of the distance.
So even small air gaps from dirt, paint, or uneven surfaces can tank the pull force fast.
Aim for direct steel-to-magnet contact whenever possible.
Magnet Positioning
For max force, the magnet’s poles should be perfectly perpendicular to a flat, centered contact.
Any misalignment, especially shear angles, will slash the pull capacity.
Edges are weaker than the center too.
Material and Surface
Obviously, magnets only attract ferromagnetic metals.
But the type and condition of that metal is also key:
- Low-carbon steel works best. Alloys are often weaker.
- The steel needs to be thick enough to absorb the full magnetic field.
- Rough, rusty, or dirty surfaces create air gaps. Clean and smooth is ideal!
Magnet Size and Shape
Generally, bigger and thicker magnets have more pull due to greater surface area and reach.
But the shape matters too.
Elongated designs can focus the field for more force.
Matching the magnet to the contact surface helps as well.
Tips for Maximizing Pull Force
Alright, so how can you put this knowledge to work?
Here are some pro tips for achieving peak pull force:
- Always choose the optimal magnet material and grade for your application and environment. When in doubt, go stronger!
- Use clean, flat, low-carbon steel surfaces. Avoid thin sheets, dirty or rough areas, and uneven shapes.
- Minimize air gaps at all costs. Get as flush and gap-free as you can. File down high spots if needed.
- Pay attention to positioning. Align the poles properly and avoid off-center or angled placements.
- For applications with unavoidable gaps, size up the magnet to compensate for the force reduction.
- When coupling multiple magnets, experiment with attractive vs. repulsive orientations and spacing to maximize the field.
- Regularly test and track your magnets’ strength with a quality pull test kit. Spot weakening early and replace as needed.
By putting these principles into practice, you’ll be able to select, install, and maintain magnets that deliver the full holding force you need.
Remember, the God is in the details!
Conclusion
Hope this guide has given you a solid foundation in the science and strategy of magnetic pull force.
It’s a complex topic, but understanding the key levers – from magnet grade to air gaps to positioning – empowers you to optimize your magnet systems.
Last but not least, if you need magnets with superior pull force, Osenc is always here to help.
Feel free to reach out anytime.