Stepper trouble shooting (not your typical case... I think)

Hello! So we built an LMS X2 conversion a while back. Pretty proud of it, as we've done everything from scraping the ways to reinforcing the column. We use a CNC Fusion kit with three 425oz in steppers from Automation Technologies. We used one of their kits that comes with KL4030 drivers. We've had this thing going on two years and have become quite familiar with it. The issue we're having now is that the x-axis motor is no longer able to push the table. I tore the x-axis down and rebuilt it, making sure the gibs are properly adjusted and that the ball screw is aligned from each end and the ball nut.

I used the machine one night, quite heavily, with absolutely no issues. After making several parts, I shut everything down. When I returned the next morning, I fired everything up, but for some reason the x-axis refused to move, making that god awful "WHEEEEEEEEERRR" noise. Absolutely nothing was done to the machine after I shut it all off the previous night. I realigned everything, but no joy. None of the other axis are having problems. Here's what I noticed:

1) I am able to pretty easily turn the motor by grasping the shaft coupling (not coupled with the ball screw, mind you, just holding the motor in my hand) and turning it. If memory serves, this used to be much much harder.

2) If I disconnect the motor from the ballscrew and hold it in my hand, it will make the awful noise just from me lightly jostling it while running the motor.

I need to compare this to the other motors, see if they have comparable features. If it turns out that the other motors seem to not have these same features, my question to you is would this be an issue with the motor or the driver? I think I can rule out resistence in the table, as even if I loosen everything up it seems to struggle. Thoughts?

Do you use Mach? If so, double check all of the settings for your steppers. It could have been corrupted.

A stepper shouldnt offer any resistance if it has no power applied. If the controller is powered up, you should get a very firm resistance if trying to turn it by hand. Of course you can turn it but it will take an effort.

Is there a way you can swap the stepper for a momentary test? Try a different stepper to that driver. This will confirm whether it is the stepper or the driver.

Thanks for the reply! So I was able to isolate the problem to the motor. Interestingly enough, the whole thing goes fine for about 5 minutes after power up. Shortly after that, it goes sour. Replacing the motor with the Z axis motor resulted in the axis having trouble free movement.

During all of this I discovered what I think is a Mach issue. When moving the x axis, if I move the y axis simultaneously, the x axis jumps when the y axis changes direction. Only occurs with backlash comp enabled. Is this normal? I'll post it to the mach forum as well.

Each axis will implement the backlash comp just before a reversal of direction. You can hear it depending upon which % of rapid speed you have the BC running. Just verify which version of Mach you are running on that forum and read what bugs it has. All versions have bugs. It just depends on which bug affects your work.

Thanks again, I'll be sure and check. The oddity is that the x axis is bumping when the y axis changes direction.

What are you using for a BOB? Are your cables shielded? Run side by side possibly?

I'm using a C10. The wiring is quite close together, but I'm doubting signal noise being the issue as it only occurs when backlash is enabled. I think it's normal behavior that I just never noticed. I cut a circular pocket that was perfectly round, so it seems mach knows what is doing.

Personally I like Mach. Of course I dont have any experience with anything else. I have had a few problems over the years. Some explainable, some not. Eventually I get it sorted out. It is great for its price, support and ability to use it on as many hobby machines as I desire.