Testing and Certification
Permanent magnets are manufactured with the magnetic characteristics being the primary focus. The chemical composition of the material is “adjusted”, as required, to achieve a particular blend. Due to factors that are typically difficult to control, blending is the most desirable method of ensuring that the required magnetic characteristics have been met. Factors that are difficult to control are those factors that are either unknown, or current technology does not exist to be able to provide a close enough control to ensure repeatability. For example, impurities may influence the final outcome of the permanent magnet. However, it may be easier to use “blending” technology rather than further refining the material to achieve the desired characteristics.
In this article we describe different types of tests and certifications that are offered, and where applicable, some cost estimates are given. Actual costs will depend on the type of test, extent of testing, sample size, frequency, the type of data processing desired, and the type of documentation required (MCE is ISO9001:2008 and SAE AS9100C certified; our documentation meets the requirements of these certifications). Here are some of the tests offered:
Certificate of Conformance
Certificate of Conformance
Also know in the industry as Certificate of Compliance, a “C of C” is a certification provided by MCE that states that the products being shipped to you comply with all the specifications submitted to us at the time of the order. It also states that we maintain quality files on hand that are open for inspection by authorized personnel. All orders that we process will be accompanied by this certification, even if you did not request this. There is no charge for this certificate. This certification can be found on our packing slip that accompanies the product.
This is a “test report” where the test is magnetic in characteristics. This is a plot of the second quadrant hysteresis curve and shows how the magnet material will behave under different operating conditions. This type of test is only done on a sample from a material production lot. This information can be provided if your requirements state this at the time the order is placed and we have agreed to send you this data. For traceability reasons, this data may be reviewed at no additional charge. If you need us to run this test on your sample, the test ranges from $350.00 to $600.00 depending on sample condition, type, number of curves required, and other factors. For more information on getting this test done, see BH Curves - Testing Magnetic Materials under Services. This is a destructive test, the magnet can no longer be used in the field.
This is a chemical test of the base material. This is done by sending a material sample from the same lot that was used to make the parts to a laboratory that can chemically analyze this material. The benefit of this test is very limited especially since there are no benchmarks by which the material may be judged as acceptable or unacceptable. Other than giving the ability to the recipient to make the distinction as to what the basic material is, there is no real value to this test. Some customers, however, require this test. The cost of this test is assessed at $300.00. The test is a destructive test and the magnet sample cannot be used in the field.
Mechanical tests such as Yield Strengths, Young’s Modulus, and other such tests are available at additional costs. Mechanical Tests are not acceptable as a means of accepting or rejecting a lot of permanent magnet materials. The test is a destructive test and the magnet sample cannot be used in the field.
Flux Density and Total Flux Tests
These tests are conducted internally to ensure compliance. However, unless predetermined and agreements to standards have been established, MCE takes these readings only for reference purposes. Flux Density readings are taken using a gaussmeter, while the Total Flux readings are taken using a fluxmeter and a helmholtz coil or a search coil. The costs of these tests depend on the quantity of magnets that need to be tested, the documentation and subsequent analysis required. These tests are non-destructive and magnets that have undergone these tests may be used in production.
Humidity Chamber Age Test
Humidity Chamber testing is occasionally required by some customers to force age a magnet or magnet assembly so as to predict how the magnet will behave after a specific length of time. Correlations should be developed by the customer. The humidity chamber tests are typically performed to determine the longevity of a coating or plating on Neodymium Iron Boron (sintered) magnets only when the magnet is expected to see extreme conditions or a very high reliability is required from the plated or coated magnet. The test involves putting a sample, or set of samples, of the coated or plated magnet in a humidity chamber at 85% Relative Humidity, a temperature of 85°C, for a predetermined number of hours (ranging from 24 hours to 240 hours, however, 72 hours is considered a good standard). Magnet samples from the humidity chamber tests should not be used in the field; these magnets should be considered as "aged" and a short life expectancy should be assumed. Depending on the length of the test, costs will vary. Typically, a 24 hour test will cost about $300.00, while a 240 hour test will cost approximately $1200.00 (You can assume the cost to be $200.00 to initiate, and then $100.00 per 24 hours that the test is conducted). Maximum sample size cannot exceed 20 lbs. for one test.
Autoclave Age Testing
Autoclave tests are occasionally required by some customers to force age a magnet or magnet assembly so as to predict how the magnet will behave after a specific length of time. Correlations should be developed by the customer. This test is generally performed on Neodymium Iron Boron magnets that have been plated or coated. The objective of this test is to determine the longevity of the coating or plating. The test is usually conducted at 120°C, 2 atmospheric pressure, for 24 hours. The test is a "pass/fail" test, the requirement being that upon removal of the samples no oxidation or peeling should be observed. This is also a very stringent test for very demanding applications. Typical costs of this test start at $900.00. Our Process K1055 requires that we conduct this test on a random basis, however, results are not released to the customer, but internally maintained. The customer is not charged for this test when Process K1055 is used. If the customer does require MCE to submit the results of the test, a charge of $900.00 will be assessed per sample lot. Magnet samples from the autoclave age tests should not be used in the field; these magnets should be considered as "aged" and a short life expectancy should be assumed.
Conventional Age Testing
Conventional age testing is also commonly known as the "boil test". This test is done by taking a sample and exposing it to 100% Relative Humidity, 100°C, 3 hours continuously. After this, the sample is removed from the chamber and evaluated. The tests are used on coated and uncoated magnets, typically Neodymium Iron Boron (sintered). Results are correlated with customer requirements and the test is used on a "Pass/Fail" basis to accept or reject a production lot of magnets. This test is inexpensive (typically costs range from $125.00 to $185.00 per test, depending on documentation type, sample size and evaluation requirements). Magnet samples from the test should not be used in the field; these magnets should be considered as "aged" and a short life expectancy should be assumed.
Pressure Cooker Testing
This test is done by taking a sample and exposing it to 100% Relative Humidity, at high pressure (typically 2 atms) for a predetermined length of time (12 hours to 24 hours). After this, the sample is removed from the pressure cooker and evaluated. Care must be taken to ensure that the pressure cooker does not run out of water. The water must be distilled water so that contaminations are not present. This test can be done on coated or uncoated magnets, depending on customer requirements, typically on Neodymium Iron Boron (sintered). Results are correlated with the customer requirements and the test is used on a "Pass/Fail" basis to accept or reject a production lot of magnets. This test is inexpensive (typically costs range from $300.00 to $450.00 per test, depending on documentation type, sample size and evaluation requirements). Magnet samples from the test should not be used in the field; these magnets should be considered as "aged" and a short life expectancy should be assumed.
Salt Spray Testing
This test is also used to force age the magnet, typically Neodymium Iron Boron. This test is generally not performed for production lots, but rather internally to qualify certain blends of materials. Should a customer require this test, each test will cost $1500.00 and generally will take about 2 weeks. A sample or samples of magnets are taken from a production lot, then exposed to a continuous salt spray for a predetermined period. The test is a "Pass/Fail" type of test. Magnet samples from the test should not be used in the field; these magnets should be considered as "aged" and a short life expectancy should be assumed.