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The manufacturer of the brushless motor does not specify a lifetime for the particular motor I am using (BLDC5-R-57BL120L2.) For my application it is essential that the axial and radial movement of the shaft as result of bearing wear remain within tolerances.

I was thinking of putting two screws very close to the shaft, so when the bearings wear out too much, the shaft comes in contact with both screws, completing a circuit. What I do not like about this approach is that it does not give me an early warning when the motor is about to fail. It only works for radial movement of the shaft, not for axial movement. It also ruins the motor shaft and the screw contact.

How would I detect the radial and axial movement of a motor shaft as a result of bearing wear of a brushless DC motor?

kva
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  • Choose a motor with the specifications you require. Choose a motor with a data sheet. [What to check for when buying an electronic component or module](https://electronics.stackexchange.com/questions/504044/what-to-check-for-when-buying-an-electronic-component-or-module). – Andy aka Sep 08 '20 at 09:24
  • *How to detect brushless DC motor wear* — You don't. If you don't trust the bearings, don't buy it. – Janka Sep 08 '20 at 09:37
  • I have seen vibration analysis in the frequency domain being used for detecting bearing wear; no idea how they exactly do that, though. – ocrdu Sep 08 '20 at 10:44
  • @ocrdu The motor supplier suggested this as well, but could not follow up on a concrete solution. I imagine you need to characterize your entire system including the load on the motor and the housing the motor is attached to. I cannot afford to actually test the motor for years and wait until it fails, so I am not exactly sure how much vibration is too much vibration. – kva Sep 08 '20 at 10:45
  • I suspect that a detection system that will meet your requirements will cost quite a bit more than the motor. Find a motor supplier that will provide statistics with credible evidence to assure the motor reliability. Be prepared to pay a multiple of the price shown in the link you provided, perhaps 10X. –  Sep 08 '20 at 13:08
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    I’m voting to close this question because bearing wear is a Mechanical Engineering subject, not an Electrical Engineering one. Yes, there are some coil and a drive circuit in there, but they are not the subject. And a solution might involve electronic sensing technologies or software, but choosing what to sense and how to interpret it is the meaningful part, and that's in the Mech E domain. Most competent engineers have some versatility, but the subject matter is not aligned with the purpose of this particular SE site. – Chris Stratton Sep 08 '20 at 13:53
  • Unless it's going somewhere inaccessible (like in orbit) use a dial gauge mounted to the assembly, push/pull the shaft and measure deflection as part of routine maintenance. –  Sep 08 '20 at 16:13

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