How Long Do Magnets Last and What is the Magnet Lifespan on a Shelf?
We are asked many times about the shelf life of permanent magnets. The simple answer is, no, there is no shelf life; however, as all things go with magnets, it is not that simple…
Magnetic Pull Force & Strength Explained
Breakaway force, holding force, fixturing force – “How can all of these represent the same measurement?” a younger engineer recently inquired. Engineers and non-engineers alike can be puzzled trying to understand some of the commonly used – but potentially misinterpreted – terms related to the concept of a magnet’s pull force…
Does Temperature Affect the Strength of a Magnet?
The maximum operating temperature of a magnet is an important property, but it is simply the point beyond which the magnet will experience an irreversible loss in net magnetization. In actuality, a magnet will lose net magnetization as soon as it starts to heat up. This loss is called “reversible” as it is recovered as soon as the magnet cools back down. While avoiding irreversible loss may seem to be the primary concern, even reversible loss can cause a negative impact on a magnet’s performance because while the magnet does not permanently demagnetize, it may not generate enough field for a given application at a particular operating temperature.
How Air Gaps, Workpiece Conditions, and Operating Temperature Affect Magnetic Pull Force
In sizing and selecting magnets and custom magnetic assemblies, it is important to ask a number of questions about the working area in which the magnet will operate. The answers to these questions help deliver a higher level of success in providing a magnet that meets the fit, form, and function of the application. Three areas of concern that we’ll address are: air gap relative to holding force, workpiece conditions, and operating temperature. All of these represent important conditions for the magnet’s ultimate performance…
Magnetic Saturation: Understanding Practical Limitations to How Much Induced Magnetism Can Be Achieved in a Workpiece
There are limits to how much induced magnetism is possible in different materials and similar workpieces of varying size, shape and configuration. The principle of magnetic saturation observes that there is a point of diminishing returns at which attempting more externally applied magnetic field (H) will give rise to no additional magnetic induction (B). Increasing the thickness of a workpiece is generally beneficial. However, these changes will likely impact cost, mass, and possibly ease of manufacturing. It is therefore beneficial to understand and control for the magnetic saturation of materials during the design stage…
How to Qc (Quality Control) Magnet Strength
How do you QC a permanent magnet, magnetic assembly, or a piece of equipment utilizing magnets? There are several methods which will pass a Gage R & R, but they are generally unknown to people outside of the magnet industry…
What Is Magnetic Permeability?
A material’s magnetic permeability refers to its ability to align itself with a magnetic field. A high magnetic permeability indicates that a material easily aligns itself to a magnetic field. If it is difficult to align to the magnetic field, the material is said to have low magnetic permeability. Magnetic permeability can also be thought…
Choose the Optimum Magnet Grade: Know Why Magnets Demagnetize
In the absence of external influences, a commercially viable magnet alloy should remain magnetic for hundreds of years. The alloy’s resulting field may degrade slightly from aging effects, but for the most part it should remain an effective magnetic field source. With that said, most magnets used in real world applications experience many external demagnetizing conditions. A partially demagnetized magnet may greatly impact operational performance that may result in failures in the field…
Scenarios & Techniques for Machined Magnets
The use of as-cast or near net shape magnets is almost always a preferred design path, but this is not always feasible. This is where machining comes into play. Some of the machining techniques common in the metalworking arena are modified and adapted to create special design features or to achieve specified tolerances on magnets. …
What is Maximum Energy Product / (BH)max and How Does It Correspond to Magnet Grade?
The term Maximum Energy Product ((BH)max) is a commonly used, but often misunderstood figure of merit of magnets. The (BH)max is an Energy Density and it is oftentimes used to denote grade. The grade convention is especially used for Rare Earth magnets, (Neodymium Iron Boron Magnets and Samarium Cobalt Magnets). For instance, a grade 48 Neodymium Iron Boron magnet will generally have an advertised (BH)max of 48 MGOe…