Capacitive discharge demagnetiser
AC demagnetiser

Hirst Magnetic Instruments Ltd. design and manufacture demagnetising systems capable of reducing the existing flux in magnets, ferrous material, magnet housings and equipment.

Hirst’s range of easy to use demagnetising systems offers flexibility and control at both high and low production rates. They can be supplied for manual operation, with suitable PLC interface controls or integrated with other Hirst products.

Models are available in each range suitable for demagnetising permanent magnets or ferrous material.

Demagnetising materials, (or degaussing or deperming as it is also known), plays a vital role in the flow of work of many industrial processes around the world.

Components may become magnetised as part of the production process or are supplied magnetised (intentionally or otherwise). They often need to be demagnetised to avoid production problems, to make handling easier or to recycle components. It is therefore necessary to remove, or greatly reduce this unwanted magnetism.

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 Demagnetiser

AC Demagnetisers are suitable for small, low field demagnetisation, i.e. cathode ray tubes and certain steel applications, machined parts etc.

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. AC Demagnetisers have become less popular due to the Health and Safety requirements of limiting exposure to magnetic fields. While they remain a viable system for some automated processes, manual operation is now problematic.

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.

Precision Demagnetiser PDM

Precision demagnetisers are used to achieve very accurate demagnetisation.

With this technique, a pre-programmed demagnetising wave form is generated. The frequency and decay time base of the applied AC demagnetising field is accurately controlled. This is often required for components of a large mass. Systems can be a single axis or two and three axis systems for the best demagnetisation processes.

Mechanical handling

Hirst’s demagnetiser systems are available with a number of loading options. The various typical configurations are described below. Please note if you do not see what you require then just ask! We manufacture systems to your requirements, so if you have specific loading and handling requirements we would be happy to discuss these with you.

Manual loading

The most basic system is manually loaded and unloaded. The operator would load the part to be demagnetised into a fixture and press the start button on the demagnetiser unit.

Conveyor systems

Conveyor systems are ideal for integration into existing production lines. Typically the parts would be loaded or fall onto the start of the conveyor and be carried into the demagnetisation fixture. A “magic eye” senses the part is at the correct position and initiates the demagnetisation pulse. Additional “magic eyes” can be added to stop the system if the conveyor belt is not emptied or to fit in with an existing production flow.

Interface ports

The interface ports of the MCSD and MD series are suitable for integration in mechanical handling systems where the parts to be magnetised are fed to the fixture by means of an appropriate loading and unloading system and a fully automated system can be developed.

Various I/O options are available and include 12 or 24v DC logic, 110 or 240v AC logic and RS232 ports. The exact format of any interface port fitted is designed to meet the customers requirements.

Hirst Magnetic Instruments design and build mechanical handling systems specifically to interfacing with our demagnetiser systems.