Types of Demagnetising Systems
Hirst Magnetic Instruments manufactures five types of demagnetising systems each suitable for a particular type of application.
The type of demagnetiser chosen will depend mostly on the type of material to be demagnetised and the effects of any surrounding material on the demagnetisation process.
The required maximum magnetisation level will also determine the type i.e. how much magnetic strength is acceptable after demagnetisation.
AC Demagnetisers are suitable for small, low field demagnetisation, i.e. cathode ray tubes and certain steel applications.
These are the simplest of demagnetisers. A coil or demagnetisation fixture is connected to a mains supply that may or may not be controlled by electronics to control the magnetic field’s magnitude. For the smallest and simplest of cases a hand held AC demagnetiser may be used.
Either the fixture is moved away from the work piece, or the work piece is moved away from the static fixture. Either way the resultant demagnetisation is very dependent upon the speed of relative movement. If this relative movement is made by an operator, then the efficiency of the demagnetisation process can be seriously impaired.
Resonant AC Demagnetiser
A variation on a mains demagnetiser is to incorporate a resonant technique to offer higher fields with low continuous input current. Dependent on the application, this can achieve effective demagnetisation without the need for component removal from the demagnetising location.
This technique can be adopted for small and large applications.
Capacitive Discharge Demagnetising Systems
Hirst Magnetic Instruments Ltd. offer capacitive discharge demagnetising systems suitable for demagnetising permanent magnet materials as individual components or as part of an assemblies.
These techniques can be used to demagnetise individual parts or on mass depending on the application.
Capacitive discharge demagnetisers are the most popular form of demagnetiser.
Charging up a capacitor bank and discharging this energy into a demagnetising fixture can generate demagnetising fields much larger and can cover a much larger volume than AC and precision systems.
Hirst Magnetic Instruments incorporate microprocessor technology in their demagnetisers to safely manage the charging and discharging of the machine during the magnetising operation making it very safe to use.
Capacitive discharge systems can achieve high production rates and be part of an automated system with conveyor or other mechanical feeding systems.
The following describe the various capacitive discharge units with their appropriate features and applications.
The MCSD is the ideal general purpose machine where the ability to magnetise and demagnetise from a single unit is required. With the PLC connector and a serial port the ability to automate these units makes them very versatile.
The MCSD series has all the features of the MCD series plus the ability to apply set and magnetisation pulses. The MCSD can also apply reverse polarity pulses.
The MD range of demagnetisers is fully microprocessor controlled. The microprocessor also performs fault monitoring for system protection.
With the options to add PLC connections and RS232 serial port for external control and automation makes the MD range of demagnetisers very versatile.
Precision demagnetisers are used to achieve very accurate demagnetisation.
With this technique, a pre-programmed demagnetising wave form is generated. The frequency and decay timebase of the applied AC demagnetising field is accurately controlled. This is often required for components of a large mass.