Manufacture of special industrial demagnetizers since 2010
How a demagnetizer works ?
Industrial demagnetizer: operating principle
As it passes over the demagnetising coil, the part to be demagnetised runs perpendicular to the lines of force of a magnetic field created by an electro-magnetic circuit.
As it passes in front of the circuit, the part is subjected to a magnetic flux that increases until it reaches saturation, then decreases to a value close to zero.
The electrical originality of the system lies in the use of a series Self-Capacitance circuit that resonates when the part to be demagnetised passes by, which allows a low consumption of active energy.
A coil capable of subjecting the part to be demagnetised to an induction at least equal to that of saturation.
Mileresis industrial demagnetizer : Electrical diagram
Our system acts efficiently to demagnetise parts with simplicity and energy saving. An originality that allows the circuit to enter into resonance when the part to be demagnetised passes by, so that no energy is consumed in a vacuum.
The creation of the decreasing magnetic field only takes place when the part is perpendicular to the demagnetising coil. The magnetic circuit is then closed by the part to be demagnetised.
How does magnetisation work?
The basic priThe basic principle of magnetising and demagnetising tools is a process called the 'hysteresis loop'. To magnetise a tool (usually made of steel), you bring it in an orderly fashion close to a strong magnet and then remove it. The magnetic field inside the tool increases, the tiny magnetic domains inside line up, and when you remove the tool, some of these tiny magnets remain in order.
The steel has gone through a loop of increasing and then decreasing magnetic fields, but the removal step leaves a residual field. So when you trace the field through the steel, you get a loop - this is the hysteresis cycle.
To demagnetise, the workpiece is passed through a series of decreasing hysteresis loops, going essentially in the opposite direction and being exposed to successively lower field lines.
When a ferromagnetic material, such as iron or steel, is exposed to an external magnetic field, the material becomes magnetised.
What happens inside a ferromagnetic material during magnetisation? The external magnetic field (H-field) aligns the elementary magnets inside a material. These elementary magnets are not freely arranged within the material, but are grouped together in "domains".
These domains (also called Weiss domains) are separated from each other by domain walls. The size of the domains is usually less than 100 µm (for non-magnetised materials), the thickness of the domain walls is only a few hundred atomic distances.
The domain walls are displaced in the material as the external magnetic field increases and due to the magnetic flux (B-field) associated with it. However, this induced magnetic flux does not increase uniformly, but rather in small non-continuous jumps called Barkhausen jumps. As the magnetic field increases, larger and larger domains are formed with the corresponding regular alignment of the elementary magnets. In the ideal scenario of magnetic saturation, a single large domain with magnetically anchored elementary magnets is formed. Ferromagnetic materials retain a higher or lower magnetism after magnetisation, also called residual magnetism or remanence.
Why does a part demagnetise?
If objects are magnetic, they can be demagnetised. With a coil that changes polarity, the elementary particles become "confused" and lose their uniform alignment. Eventually, the magnetism is below the measurable threshold and is no longer considered.
Demagnetisation is achieved by using the alternating magnetic field to move the uniformly aligned elementary magnets into a homogeneous disorder and to generate as fine a domain structure as possible. The demagnetising power that must be applied for this is defined by the field strength. This depends on the current, the coil aperture, the coil length and the number of coils.
Demagnetisation is successful if the demagnetisation pulse is designed in such a way that the polarity of all elementary magnets, including those inside the material, is reversed in one direction once the required maximum field strength is reached.
A fine domain structure is generated by the frequency shake effect. This first occurs inside the component. However, the polarity of the elementary magnets in the outermost region and on the surface continues to be reversed until the applied demagnetising field decreases completely. The component is thus demagnetised from the inside out.
A demagnetising device or entmagnetisierungsgerät considerably reduces the residual magnetism/remnance to a value close to zero. They are used to demagnetise all types of machine parts, tools, cutting plates and other products.
How to demagnetize a part?
Ferromagnetic materials that include alloys contain a relatively large amount of magnetism after being exposed to a magnetic field. To remove the residual magnetism, the part must be subjected to an alternating magnetic field that is gradually reduced to zero. Industrial demagnetizing systems are used for this purpose, which effectively remove residual magnetism in various materials and workpiece sizes and restore the desired functions to lifting or load clamping magnets.
Mileresis demagnetisers are ideal for machine builders, subcontracted machinists (grinders) or factories that manufacture (ball) bearings, sensitive mechanical parts (aeronautical, automotive, railway, aerospace industries, ...).
The MILERESIS 1000 T15 demagnetiser is ideal for parts with a diameter of 20 to 150 mm.
For parts with a diameter of between 50 and 250 mm, the MILERESIS 1000 T25 demagnetiser is perfectly suited.