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Hirst recently completed two orders for magnetising and calibration solutions, for two bespoke magnetic parts used in the aerospace industry.

In both cases, we designed and built custom tooling compatible with a J2A fixture, to suit clients’ parts. The J2A is a widely used fixture for magnetising and demagnetising small assemblies. It is very adaptable, and over the years Hirst has made hundreds of these fixtures.

We still have the original hand drawn blueprints (and yes, they are actually blue), from 1965, when the fixture was first introduced. We even have customers out there still using some of these original fixtures frequently. We think 50+ years’ service represents fairly good value for money!

We have made a few minor changes over the years, and it is now all drawn up in our 3D CAD system, but the design has changed little in all this time.

Back in the 1960s we would have paired this with a MC2 magnetiser.

Time has moved on a little on the magnetiser side, and these days we supply the J2A more often than not with our MCSD100J, a desktop magnetisers which can be linked up to a gaussmeter and a PC for calibration and automated sequences.

If you have a part that requires magnetising, demagnetising, or calibrating, we can certainly come up with a way of doing this for you. We have the knowledge and experience, and love a challenge!

With the sudden and unexpected Death of John Dudding the previous managing director. Hirst have re-organised their senior management team.

Suddenly on Tuesday 11th May 2021, John aged 65 years of Falmouth. Dearest son of Molly, beloved husband of Julie, loving father of Jack, Bethany, Lamorna and Mawgan, much loved grandfer of Jonah and Erwin, treasured brother of Kim and uncle of Barrie and Ocean.

John had been Managing Director of Hirst since 1986. He had seen a number of changes and revolutions in magnetiser and magnet measurement techniques. Including introducing the first microprocessor controlled magnetisers in the 1980s and his mission was to get the Pulse Field Magnetometer as an internationally accepted standard for the measuring of magnets. John devoted is career to the development and research of PFMs. This research and the work on international standards still continues with Hirst.

https://ukmagsoc.org/events/magnetisation-measurement/

Hirst’s Pulse Field Magnetometry and Open to Closed Measurement Technologies
by John Dudding, Robin Cornelius, & James Clewett of Hirst Magnetics

Hirst’s history of practical, innovative magnetising and material parameter testing techniques is coupled to its long term aim of reinterpreting the open magnetic circuit measurements of magnet materials. Hirst’s 25 year development of Pulse Field Magnetometry (PFMs) led to the writing of IEC Technical Report TR62331 and is currently leading the international team working on the new International Standard IEC 60404 part 18 detailing the PFM technique. Hirst has overcome many of the perceived limitations of the PFM technique but the ultimate goal has always been to use the PFM technique to provide accurate, repeatable and fast Permeameter, (BH Tracer,) closed circuit like results for engineering and quality control. As well as a brief overview of its magnetising technologies which have also made progress, Hirst will describe the workings of PFMs, the limitations of the Permeameters and also its new PFM process*, enabling Open to Closed (O2C**) measurements of rare earth permanent magnet material and finished magnets in industrial shapes. This process enables, fast, repeatable measurements, between +210 °C and -40 °C with an accuracy currently under a confirmation review in an active joint project with the National Physical Laboratory (NPL) Open to Closed measurement is expected to open a new era in the magnetic measurement of magnetic materials at a time when efficiency is powering our Green Technology revolution. Shaped pre magnetised components will at last have a pre-assembly and pre magnetisation QA capability. Patent applied for. ** Registered Trade Mark

Hirst has now developed a significant advance of the PFM process with mathematical support from the University of Exeter. These new PFM self demagnetisation field function (SDFF) units allow closed-circuit magnetic measurements to be made in open-circuit circumstances, something which has not been possible before. 

This is an essential step needed for the characterisation of actual production magnets prior to assembly and magnetisation. 

This is an industry first and solves a high-value industrial market challenge.

This technology extends the PFM open-loop process, allowing closed-loop measurements to be made by using a proprietary new field interpretation model operating on a proven technology platform.

This enables a high-yield volume permanent magnet motor manufacturing supply chain and quality assurance operations worldwide. 

The SDFF technique can be applied to all ‘open’ magnet characterisation techniques, in the laboratory or factory, where it can offer potentially 100% yields by ensuring that every magnet in the assembly has the same, specified characteristics required by the application.

Essentially this advance enables a high-yield volume manufacturing of permanent magnet-based products, ahead of other techniques.

https://www.iop.org/hirst-magnetic-instruments