[N2950H]

It's been a rough night. I'm 98% done with my build, and as I was moving the gantry around I managed to run it into the hard stops. Contrary to what I've heard countless people say, the stepper motors (620 oz-in) did not stop right away. They kept turning and making a lot of racket...this went on for about 5 seconds before I was able to shut it down. It's not really a hard stop, they are made of rubber so there was some chugging back and forth against them. It doesn't look like the rack/pinion are stripped, so I'm not sure what was making all the noise. My Y and A motors are slaved, and all the noise seemed to be coming from the Y motor.

I pulled power from the motors and the gantry seems to move alright without too much effort. Nothing seemed horribly damaged. Re-applied power to the motors and tried to move the Y-axis 1/2 inch and it moved, but made a similar awful noise.

Did I destroy my stepper motor(s)?

[N2950H]

Played around with it a little more, and the noise is only there just as the Y axis starts moving and right before it comes to rest. Maybe just a low RPM issue? Not knowing the cause, I'm afraid to keep running it around the table while troubleshooting since I don't want to hurt the motor if I didn't already.

[bhurts]

I solved this same issue by making the rack just slightly smaller then the rails. This allows the gear to drive off the rack just before hitting a stop. It does not prevent hitting the stop but it keeps the motors from being able to continue spinning without actually driving the axis.

Ben

[N2950H]

So that would probably keep it from happening, but now that it has happened...I don't know if I hurt the motor or how to quiet things back down. It sounds awful when it starts and stops.

Also, it does not do it all of the time. I cycled power to the motors for some other stuff I had going on, tried it again, and everything was back to normal. Cycled power again, and not it's back. This is driving me nuts.

[bhurts]

It almost sounds to be mechanical. Try checking all connections, setscrews, etc... Also disconnect the motor and spin it by hand. Check for damaged bearings, gears, shaft, etc. Sorry as to stepper specific issues I can't be much help since I don't use the.

Ben

[N2950H]

I think I've narrowed it down to the stepper motor itself. With the motors locked (power to them), I can grab the end of the gantry where the suspect motor is and move it slightly along the Y-axis. In other words, there seems to be 1 or 2 steps worth of play in the motor. The motor also seems to vibrate quite a bit when running. Is this indicative of a bad motor?

If so, then I can't help but wonder what the heck happened. Everything I read says you can't hurt a stepper motor by stalling it out. So why didn't mine stall out when it hit the stop?

[plain ol Bill]

Swap motors from Y to A and see if it follows the move. I suspect it is mechanical also and you will still find it on the Y after the swap.

[N2950H]

One of the support folks at CandCNC told me that despite the horrific noise, the motor cannot be hurt by what I did and to check the motor for loose set screws. While the set screw which clamps the gear onto the output shaft had slipped initially, I re-tightened it and made sure it was still good even after the Y-axis motor continued to make noise.

Due to the way my wires were routed, I chose to swap motors Y and X. As expected, I no longer have an issue with the Y-axis movement, but I also do not have an issue with the X-axis movement. I don't understand how something like that awful noise can come and go.

So I guess I'm good to go now, but it wouldn't surprise me if the X-axis motor starts acting up again.

[Torchhead]

It would surprise me since I have never seen stalling a motor cause motor damage. A stepper is a magnet, two coils of wire and some bearings. If there was motor damage you can feel it if you pull the motor and turn the shaft . it will not just spin and it will have "detents" but what you are feeling for is if it binds or gets harder to turn anywhere in the 360 deg spin/ It should all be the same. If it runs smooth on the table now it is 90% probable it was something ,mechanical besides the motor. The only thing that can cause a noise is if the rotor is out of alignment with the body and something inside it physically hitting. You can pick that up with the manual spin test. That horrible grinding sound is basically the motor stalling and vibrating. It is similar to what a solenoid would do should like if it was jammed and bouncing against a rubber stop. it sounds like gears are being stripped but there are no gears . there are in fact no parts that move save the rotor. No brushes , The only time I have seen a motor get damaged was when is was physically dropped from a height to a hard surface onto its shaft. You also have a 2yr warranty on that if it is a CandCNC product and that includes motors.
TOMcaudle
www.candcnc.com

[tinky1233]

When the steeper motor first energizes (reset) it goes to a default position (A coil ON B Coil OFF) and it moves to accommodate this. If you have slaved motor it has to be in sync so when it also energizes it falls into same detent. It's possible that hard stop jolted motor out of phase and it energizes in wrong direction. You can fix this by swapping whole coils or you can loosen clutch power up motors and then tighten clutch.

[N2950H]

Thanks for the replies, guys. The motor definitely turned freely when I had it off the table with no binding. I'm half-retarded when it comes to stepper motors and electronics in general, but now that I have done some more reading and better understand how steppers work, I see how it would be very difficult to damage a stepper by running it into a hard stop.

All the same, I'll be wiring up my limit switches today just to avoid that awful noise in the future.