Rare Earth Magnet Applications
Rare Earth Magnet Applications – Magnetic Box Closures
By Tim Boettcher | Submitted On September 21, 2010
It is quite often today one will find Rare Earth Magnets used in the production of retail packaging. This is most often paper box construction which has one or more movable flaps. Often seen in high end kids book collections, DVD collections, or things like Craft type kits found packaged in paperboard. It is considered a replacement to the hook and loop type fasteners (i.e. Velcro) & magnetic pins found in older style boxes.
There are two configurations which should be considered. push pin magnets
1) Using two rare earth magnets
2) Using one rare earth magnet, and one piece of ferrous metal
Selecting which option to choose depends on a several factors:
Gap – what will be the total distance between the magnet/metal pair
Feel – how much force do you want the end user to apply when opening
Due to the somewhat fragile nature of rare earth magnets, it is usually recommended that during assembly of the box, that the two parts (two magnets , magnet/metal) not be allowed to come in direct contact with each other. This will minimize any chance the magnet could break due to shock when the box is closed.
Two Magnets – This configuration is best utilized when a stronger bond is required, and when the material is thick, creating a larger gap between them. Neodymium Magnets can be inserted into paper board which has been die-cut, or they can also be surface mounted and laminated over (or a decorative design, sticker or pad of some type could be placed over the magnet). Careful attention must be made during assembly to ensure the polarity is in an attracting configuration. Some manufactures offer rare earth magnets which are marked on the North seeking pole to aid in assembly. If office magnets are improperly mounted in an opposing configuration, they will repel and the box will not close. Magnets like to attract to each other in a very exact manner, so the two magnets will need to mate together in close proximity for the ideal bond to occur.
Magnet & Steel – This configuration is best utilized when a slightly weaker bond is desired, the material being used is not as heavy, or when overall cost is the limiting factor. Using steel as the mating piece to the magnet cuts the overall cost substantially as steel is quite a bit less expensive than the rare earth magnets. Steel discs, washers and other similar steel can be used as the mating part to the rare earth magnets for sale. Another factor which makes the magnet-steel combination attractive is the placement of magnet. Alignment of the steel piece is not as critical as the office magnets will attract well to the steel if it is over-sized or not centered. Lastly there are no concerns with polarity when using the magnet-metal configuration, as the magnet attracts to the steel equally on either the North or South seeking poles. Steel pieces are mounted in the similar ways as the magnets and box could be die-cut and the metal inserted, it could be taped in, glued in, and it could be laminated over for the totally invisible bond.
For both magnet-magnet and magnet-steel configurations there are two factors which increase the strength of the bond.
1) The diameter of the large office magnets. Larger diameter (larger surface areas) of the magnets will yield stronger the bonds.
2) The thickness of the magnet. Thinner magnets will not have as much holding strength as thicker magnetic push pins.
Just experiment. Try various configurations for your box construction. It may work better with one larger pair, or two smaller pairs. If the bond is too strong, reduce the magnets diameter, number of magnetic push pins or the thickness of the magnets or steel.
Tim Boettcher is President of Amazing Magnets LLC. Amazing Magnets LLC was established in 2002 as an internet retailer of specialty magnets. The company concentrates primarily on NdFeB magnets, as well as, SmCo, Ferrite, and rubberized magnet products targeting original equipment manufacturers (OEMs), industrial, commercial and Internet sales for both U.S. and international customers. Amazing Magnets stocks several sizes of polarity marked Rare Earth Magnets as well as several sizes of . Sales can be reached at 888-727-3327
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