[Noteworthy] Stepper Motor, Nema 34- Deconstructed

[GLCarlson]

Did you check torque?

Stepper manufacturers routinely warn against disassembly because steppers are magnetized after assembly, and the stator acts like a "keeper" to maintain the magnetic field. Disassembly weakens that field. In one reported test, the a measured 112 oz-in stepper was able to generate 70 after disassembly/reassembly. It's likely that the critical parameters include the rotor/stator spacing, not just keeping the rotor in place; even pulling an end bell may be problematic.

In light service, a loss of power might never be noticed. In other situations, it could create a serious safety hazard or a very hard to find intermittent fault (e.g., lost steps at heavier loads).

 

[Ulma Doctor]

Interesting theory, but in the real world there were no ill effects.
The equipment operated by the stepper that i reduilt sees service 7 days a week.
Just because a manufacturer says something does'nt make it true

 

[GLCarlson]

So you didn't measure the torque..... and don't really know if the stepper now meets spec. Thought so.

As noted, one may get away with this if the stepper isn't stressed. Looks like that's the case here.

Others may not be so lucky.

 

[mmprestine]

This is a false theory that has been passed on to often. There are no ill effects from stepper motor disassembly.

 

[Ulma Doctor]

No i did'nt dyno test the stepper, i did something more realistic, i put it back into operation.it carries its rated load just a brand new stepper.
If you want what i did to be wrong in your eyes,
congratulations!

 

[John Hasler]

Stepper manufacturers routinely warn against disassembly because steppers are magnetized after assembly, and the stator acts like a "keeper" to maintain the magnetic field.

That *may* have been true for steppers built with the old alnico magnets but is unlikely to be a problem with modern rare-earth ones.

 

[RJSakowski]

Older magnets made from a high carbon steel or Alnico required keepers because the magnetic domains reoriented over a period of time and keepers slowed that process down. Most magnets escape their keeper for some amount of time. There are countless examples of magnets that have never had a keeper.

While it may be true that a magnet has an initial instantaneous loss of flux when a keeper is removed it's not something that I have ever witnessed in more than sixty years of dealing with magnets. But then I can't honestly say that I have ever encountered a virgin magnet.

IMO, a magnet removed from a keeper for a reasonably brief period of time will not suffer great losses.