There are two different categories of flexible magnets; magnetic sheet and extruded magnetic profiles which are both made in different ways.
Flexible magnets can be extruded into profiles which can be coiled, typically in 10 or 30 metre rolls, and then used for applications such as shower door or refrigerator closures. The cross section of an extruded magnetic profile can have detailed protrusions that allow it to slide into a mating aluminium extrusion and remain captive with only the front magnetised edge showing.
During manufacturing, the flexible granular material is heated until it starts to melt and then forced under high pressure using a screw feed through a hardened die which has been electrical discharge machining (EDM) wire eroded to have the desired shape of the finished profile within it.
As material continually flows from the die, it cools and then passes over a magnetising fixture which magnetises the strip with either a two-pole or multi-pole magnetic configuration.
Most flexible magnets are magnetised with stripes of magnetic poles but on one face only, the other face is not magnetic. The extruded profile can be a rectangular section to produce a magnetic strip which is often referred to as magnetic tape and this can be laminated on the non-magnetised face with high-performance double-sided adhesive tape. Two identical strips can be magnetised with mating polarities so that when they attract each other they line up and meet exactly, one being NSNSN and the other SNSNS for example.
Magnetic sheets are produced using a calendaring process, and most of which tend to be 610mm wide and up to 30meters in length. They can be as thin as 0.5mm, but typically tend to be 0.76mm in thickness.
Flexible magnetic sheet is magnetised on one side only with very fine stripes of north-south-north-south polarity running down the length of the sheet. The non-magnetic side is often laminated with white or brightly coloured vinyl. The sheets are very flexible and can easily be cut with a trimming knife or scissors.
The sheets can be ‘die cut’ using a roller press and a series of sharp ‘knife type’ cutting blades which are set into a board and are arranged to form multiple sets of the desired shape. Using this technique, many identical simple shapes can be cut quickly with ease.
Magnetic sheets are naturally a brown colour and when laminated with vinyl, they can be printed upon using screen printing techniques.
Flexible sheets are often used for point of sale and advertising, particularly for cars. Taxis and driving school livery can be easily added and then removed when the car is used privately. The same is true for company cars showing company logos in the week, which are then removed at weekends. In these applications, meticulous cleaning and flat storage is essential to prevent attracted ferrous particles getting attracted to the magnetic surface of the sign and then becoming trapped in between the sign and the car. Good housekeeping will maintain the car’s paintwork.
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