On 2012-07-20, Bob La Londe wrote:
Grainger price (not logged in) shows as $242.50. Ebay shows them for $75 to
$180.

I got 4 of them along with 3 12 volt cart motors and a 24 volt gear motor
(RPM unknown, but I may have an immediate use for) the other day for $40
total. The guy said he just wanted to get rid of them and start with motors
built for the purpose for his application. (Building a CNC plasma table) I
can see one reason right off the bat he might not have wanted to use them.
They are single shaft. He would have had to mount his encoder somewhere
other than on the convenient back shaft like one might on a purpose built
servo motor.

The encoder can be dealt with in other ways, such as a linear
encoder on the table to feed back its position to the controller.

However, what I consider more of a limitation is that it does
not have a built-in tach generator for speed control.

Granted, if you are using something like the Gecko servo drive,
which does not use the tach feedback at all, and simply makes the motor
behave like a stepper, then you don't care -- but if you want precise
and smooth speed control, you want the tach feedback.

A way around that could be a small permanent magnet field motor
mounted on an idler pulley which could generate the speed information
for the servo amp.

Still -- the price (from snipped info from below) certainly
sounds attractive. If you can find the small permanent magnet motors to
use as tach feedback, you will be fine. (The encoder could be on a
similar setup if you don't want the precision of linear encoders.)

Enjoy,
DoN.

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