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  • OT: Magnets?

    I have an interest in magnets and I am wondering how they are made in different shapes, wedges, etc..

    Where do I research such things?

    Thanks, Dennis

  • #2
    They are commonly made by combining the right materials, then either compressing the powders and heating (sintering) to solidify them together, or alloying and forging or otherwise shaping the alloyed material. The new type, neodymium, are powdered materials mixed and highly compressed and heated. They are then at net shape, or are cut further into sizes. Once the size and shape are made, they are coated with any of a number of materials, nickel being common, to prevent corrosion. They are magnetized last, just before packaging.

    If you look at speaker magnets, the compressed and sintered ferrite material is made into rings which are then faced, assembled fully into a speaker frame, etc, and then magnetized.
    I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

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    • #3
      Depends on what kind.

      Refrigerator magnets are magnetizable powder mixed with a plastic-rubber mix and molded to shape. Some of the harder rubber magnets can be machined to desired shapes.
      Indeed most magnets are molded to rough shape. Samarium-Colbalt and Neodymium are pressed and sintered to some shape and then sawed. For example, disk magnets are molded in rods and then sawed to thickness. Square or rectangular magnets start out as big blocks or square or rectangular bars and are then sawed and sawed and sawed.

      Ceramic magnets are molded to net shape.

      Alnico magnets are cast and machined. This are the only material that can be magnetized as a horseshoe.


      All are magnetized after being brought to final shape by subjecting them to an overwhelming electromagnetic pulse for everything but the refrigerator magnets. These can be easily magnetized with the field from a Neo magnet. I have dealt with magnetizing equipment on a production basis.
      Weston Bye - Author, The Mechatronist column, Digital Machinist magazine
      ~Practitioner of the Electromechanical Arts~

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      • #4
        Seems like dark magic to me. Any books or ?? out there that I (not being an EE or even close) could read about the way they are made with ideas etc????

        A curious mind shouldn't be wasted, even tho it has finished off a person or two......

        Dennis

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        • #5
          Magnets

          Take a look over here:
          http://www.kjmagnetics.com/categories.asp
          for some practical magnetic info and a great supplier.

          I used them to supply the N50 magnets that form the smart bits of my magnetic drive oxy-actylene pattern tracer. Helpful folks just an email away...

          paul
          Last edited by ironmonger; 06-06-2013, 01:09 AM.
          paul
          ARS W9PCS

          Esto Vigilans

          Remember, just because you can doesn't mean you should...
          but you may have to

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          • #6
            A video of the making of Alinco magnets:

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            • #7
              Not so hot video of Nd magnets being made:

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              • #8
                It is possible to drill holes in NIB magnets. It requires a carbide bit and very slow speed to avoid generating heat. The material is very flammable, similar to Mischmetal, from which lighter flints are made.
                Free software for calculating bolt circles and similar: Click Here

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                • #9
                  Originally posted by Evan View Post
                  It is possible to drill holes in NIB magnets.
                  I found it a bit difficult to remove chips when drilling. . .
                  Cheers,

                  Frank Ford
                  HomeShopTech

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                  • #10
                    Hmm- all we need now is to combine shape memory alloy with neodymium. We'll get a magnet which can be turned on and off with heat
                    I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

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                    • #11
                      Originally posted by darryl View Post
                      Hmm- all we need now is to combine shape memory alloy with neodymium. We'll get a magnet which can be turned on and off with heat
                      The principal's used bass-ackwards, for instance Weller temperature-controlled soldering irons are fitted with a magnetic switch where the magnet's attracted to the soldering tip: the tips have a disc of an alloy that's chosen for its Curie temperature where it loses its magnetic properties, a variety of alloys give different tip temperatures. The Curie temperature also occurs at the critical temperature for annealing, so if you can't pick a piece of steel up with a magnet, it's hot enough - it happens when the crystalline structure changes.
                      Rules are for the obedience of fools, and the guidance of wise men.

                      Holbrook Model C Number 13 lathe, Testa 2U universal mill, bikes and tools

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                      • #12
                        Originally posted by Weston Bye View Post
                        Alnico magnets are cast and machined. This are the only material that can be magnetized as a horseshoe.
                        Anything can be magnetized as a horseshoe, but it requires quite much costly materials (like neodymium), specal jigs and in the end costs a hell of a lot more than just clipping a couple of magnets to a piece of steel.
                        Amount of experience is in direct proportion to the value of broken equipment.

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                        • #13
                          Turning magnets on and off

                          Well, it's not really turned off, but you can counteract the magnetic field of a N50 type magnet by putting it contact, pole to pole, with an electromagnet. Kind of like a series circuit. When you apply sufficient current to the electromagnet, whose poles are opposite of the permanent magnet, the permanent magnets field will be canceled. The force to demagnetize the magnet is 3 or 4 times greater than that required to counteract it, so the effect is reversible.

                          The same principle applies to other permanent magnet types, but you would need to find out how much reverse magnetism your type of permanent magnet material can withstand without damage.

                          I thought it would be useful for concealed magnetic latches. Could also be used for lifting. Or just 'fun with magnets' applications...

                          paul
                          paul
                          ARS W9PCS

                          Esto Vigilans

                          Remember, just because you can doesn't mean you should...
                          but you may have to

                          Comment

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