Magnetic Component Engineering

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Writing Specifications for Magnets on Drawings


Data on drawings submitted by the customer is used by MCE to manufacture and inspect the parts. It is therefore critical that your drawings have the correct information.

In the absence of a specification, MCE follows the industry standard specification MMPA-0100.

Here are some guidelines that you should consider when writing specifications for magnets:

  1. After selecting the material required, you can copy the pertinent data from the material detail sheet. The drawing can state the nominal and minimum values as given for the material selected. However, occasionally, you may wish to include a maximum value, especially if your design is very sensitive. Having too strong a magnet may not always be desirable.
     
  2. Make sure to positively identify the type of finish (plating or coating) required. If you do not wish to have any plating or coating, indicate that using industry standard practices, such as a line in the "Finish" box of the drawing, or state "None".
     
  3. Use conventions on your drawings that conform to industry standards. In the US, the standard is ANSI Y14.5M. ISO standards are also popular and widely used.
     
  4. If using Geometric Tolerances, remember the six point rule:

    4.1 Specify the datums
    4.2 Establish dimensional relationships
    4.3 Determine the "dimension type" for each dimensional relationship
    4.4 Select the best geometric tolerance for each dimensional relationship.
    4.5 Select the proper modifier for each geometric tolerance.
    4.6 Establish the tolerance value for each dimensional relationship.

  5. Communicate with us! Feel free to send us a preliminary drawing to review before you release the drawing for production. We are here to help you achieve your goals!
     
  6. Make sure to identify and show the polarity of the magnet.
     
  7. If your design is demanding, you should consider putting test specifications on the drawing. For example, the test specification could give the expected flux density at a particular location from the magnet pole surface, with appropriate tolerances. Giving "total flux" readings when taken with a helmholtz coil is another way magnetic performance can be checked, and typically this is much more accurate and repeatable than flux density measurements. However, MCE always takes exception to this until parts are made for the first time and checked, or sample parts are supplied, since occasionally calculations may not be entirely accurate. After verification, MCE remains bound to achieving the results.