Ignoramus17560 wrote:

I have been doing a fair amount of scrapping CNC equipment, lately.

It works out great, typically just the ironplus copper wires pays me
back 2x what I pay for the machine, and then I am left with servo
motors, boards, hydraulic pumps, coolant pumps, etc to sell.

But, at the same time I feel that listing and saying things like "this
motor comes from an obsolete piece of CNC equipment that belonged to a
bankrupt company" does not let me get the highest value for the item.

Whiel I have no hope of being able to test boards, I do feel that I
could adequately test the motors.

So, what would constitute a good test of an AC servo motor like a red
cap Fanuc motor?

I see a few things.

1. Run it from a VFD and measure vibration
2. Somehow test the encoder.

Anything else?

I know that there are companies that buy those motors for $200 each,
refurbish and test them professionally (this involves change of
bearings, rebalancing etc) and sell for 2,000 each. I would like to be
able to do the same and can invest a few grand into scavenging proper
test setups.

You should already have most of the parts for the test setup if you
scrapped the machine, i.e. the servo drives and power supply. AC servos
aren't very likely to go bad, they're just three phase motors, nor are
their bearings likely to go bad since in use they don't see a lot of
loading. Encoders are the usual failures and just being able to power
the encoder and check the outputs on a scope should provide good
indication if they are ok.