My Series I PCNC1100 sat for the last couple of days while I was sick. I go out today to run a part, oil it up and ref all. Yikes! The X axis is howling/growling. It's moving just fine, but whenever is gets up to a rapid move speed, I got a bad howling. My immediate thought was the ball screw was ground up. After very quick troubleshooting, I am hoping that I hear the sound from the axis motor. After loosing the coupling, I am pleased to hear that the noise follow the motor.
I tear the motor apart, and find that the rear bearing is completely shot. I ordered a new one from McMaster for $9, and it looks like I'll make out cheap on this.
So here's what I found out: The electrical connection box on the end of the motor covers up a a hole, used to push out the motor shaft. (I'm glad it was there!) But, there is not a watertight seal between the electrical box and the motor housing. Enough water leaked in and rusted out the bearing. Thankfully, everything else is OK.
When I reassemble the motor, I plan to seal all the joints to keep this from happening again. It is interesting that this motor is the only one with coolant actively running over it.
Well that was my fun story for the day.