Testing magnet characteristics to evaluate new (to me) manufacturers
Testing magnet characteristics to evaluate new (to me) manufacturers
(OP)
What would be the ideal magnetic characteristics to have an independent test facility check to qualify new suppliers of permanent magnets. I would have them perform a B-H curve test and provide a Hysteresis graph of the sample at the temperatures I'm interested in. Some vendors will provide a representative Hysteresis graph for a single lot of magnets (in small quantities), but I am interested in an unbiased independent test.
I would also have them test the plating of NdFeB magnets to insure that they have a good process. I really don't know how to ask for this other than to slice the material and observe the interface of the layers.
I know that any testing I have done will not necessarily be representative of the repeatability of their product, but I would like to know that they have at least provided the material with the properties that I have ordered.
Any suggestions will be greatly appreciated.
I would also have them test the plating of NdFeB magnets to insure that they have a good process. I really don't know how to ask for this other than to slice the material and observe the interface of the layers.
I know that any testing I have done will not necessarily be representative of the repeatability of their product, but I would like to know that they have at least provided the material with the properties that I have ordered.
Any suggestions will be greatly appreciated.
RE: Testing magnet characteristics to evaluate new (to me) manufacturers
To check the plating, there are two tests: One is a salt fog test as per ASTM B117. The other is an ASTM scratch/peel test. I don't have the specification number handy now but can dig it up.
Hope this helps.
RE: Testing magnet characteristics to evaluate new (to me) manufacturers
The way we check for asymmetry is to measure the field in the centre of the magnet, and then at each edge.
RE: Testing magnet characteristics to evaluate new (to me) manufacturers
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RE: Testing magnet characteristics to evaluate new (to me) manufacturers
robertib, do you use a Hall probe for this test on the surface of the magnet? Should the field be the same across the entire surface (I suspect not)?
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RE: Testing magnet characteristics to evaluate new (to me) manufacturers
The field should be strongest at the centre of the magnet, dropping off towards the edges - but it should drop off in a reasonably uniform manner. The circumstances for using the magnet should determine how uniform the drop-off can be, some applications can tolerate more asymmetry than others.
RE: Testing magnet characteristics to evaluate new (to me) manufacturers
Agreed the teh center of magnet has strongest field, but I was wondering how you measured the magnetic field strength in the center of a magnet using Hall probes, one cannot insert the probe inside the solid magnet, right? waht i can image is to use a search coil to measure the flux to get Bd (devided by the cross section area) in an open circuit or a specific magnetic circuit.
except for cutting in pieces and testing them individually, it seems really challenging to evalaute the magentic uniformity along the magnetic path for a single magnet.
RE: Testing magnet characteristics to evaluate new (to me) manufacturers
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RE: Testing magnet characteristics to evaluate new (to me) manufacturers
RE: Testing magnet characteristics to evaluate new (to me) manufacturers
RE: Testing magnet characteristics to evaluate new (to me) manufacturers
Well I'm doing the same as a quality manager. We would check for the BH properties of the magnet and in addition to this, we would also perform "Total Flux Measurement" by Helmholtz Coil and Fluxmeter. This measurement can be correlated with the BH Properties and it is inter dependent (BH properties and Total Flux). In addition to this, Hall probe is used to measure the magnetic surface flux density at the center of the magnet.
For the plating on the surface of the NdFeB magnet, perform pull load and shear load test to conform the planting peel off from the NdFeb magnet surface. This is done by gluing a metal piece and test will be performed.
All the Best
N D Senthil Ram
RE: Testing magnet characteristics to evaluate new (to me) manufacturers
Well I'm doing the same as a quality manager. We would check for the BH properties of the magnet and in addition to this, we would also perform "Total Flux Measurement" by Helmholtz Coil and Fluxmeter. This measurement can be correlated with the BH Properties and it is inter dependent (BH properties and Total Flux). In addition to this, Hall probe is used to measure the magnetic surface flux density at the center of the magnet.
For the plating on the surface of the NdFeB magnet, perform pull load and shear load test to conform the planting peel off from the NdFeb magnet surface. This is done by gluing a metal piece and test will be performed.
All the Best
N D Senthil Ram