Re: Timing Pulley Accruacy and Servo shaft runout

> 5 thou ? on a new motor ? I shudder to think that is even possible !
>
> I would think that is scrap from the trash bin of the QC department.
> or it fell on the floor from the top of the rack.
>
> Dave

Well Dave, I retested the motors. The worst was .005" the best was
.0002". The best was a new Ametek motor.
Many were .002" runout (I tested 5 Baldors)and these new Baldor motors
came to me in a sealed factory box. The motor was shrunk wrapped to a
plywood bottom.
Boxes are in fine shape, no damage here. The Ametek that tested
so nice has a short 1.5" shaft that appears well machined.
The Baldor servos have longer 2.25" shafts that don't have nearly
as nice a finish as the Ametek servos. But the runout is there
regardless of the surface finish. The .002" motors are the ones
I plan on using on my machine and I am struggling to see if that
runout can cause any significant error. I would think that as
the belt gets tighter and looser the teeth engage a bit deeper, or
a bit shallower and that error would be a function of the tooth and
how deep it is going into the pulley. I would imagine that a spring
loaded tensioner would eliminate the runout as a source of error.
How far off base am I here?


Scott