SX3 ?motor? problems - help with debugging

[Joel779]

Just curious if anyone else has seen these symptoms on the stock motor setup. I have a call in to Griz for replacement parts, but haven't heard back from them yet.

Here is the story... When starting up, I get very little torque. Very easy to hand stall the motor below 200rpm. Run it up to 1500 and it starts making wierd noises, kinda rattling sounds. Run it up to 1800 and it's either making loud rattling sounds or ERR with stop. When it ERR, sometimes it is almost like 'jammed' and I have to give a short turn by hand to allow it to restart.

When I give it this turn by hand, there is a loud 'clunk' sound, much like a gear outta whack. Def not a good sound to hear.

Funny thing is if I start out forward, switch to reverse, it spins up smooth as silk. Doesn't make any noise or complaint at all. I pulled the belt and drive off the motor and the results are the same. Forward, ratty, reverse smooth.

Could this be a 'monday morning' bearing installation in the motor? enough out of whack that for some reason spinning in reverse allows it to seat and settle, but forward pulls it out and creates a binding?

I was thinking it might be a timing issue with the controller, but the more I think it is prob a bad bearing in the motor.

Thoughts?

[cornbinder23]

I would tend to agree with you on the bearing issue, some have had issue with the bearings, but not too many have had any issues with the motor and controller, other than not being able to interface it with Mach3
There are sources for upgraded spindle bearings here in the benchtop forum, I did this to mine as I am spinning it at 6000 rpm on a regular basis.
One more thing to check would be the pulley holder on top of the spindle, mine had the clunking noise, and still does to some extent, it was the interface between the splined part of the spindle and the pulley, I just loosely install the bolts holding the pulley so it can still wiggle a little bit and spin the spindle by hand while tightening the bolts, took about 75% of the noise away.


JTCUSTOMS

[Joel779]

Hello JT

Thanks for the response. The bearings are def the ones in the motor. My testing included removing the belt and running the motor by itself without the spindle. When I run the motor forward, I get the ratty sound, going from slightly rough at low speeds, to really noisy at 1800 indicated RPM. (remember, this is just the motor, should be smooth as silk.

One other thing, as I mentioned, again with the belt off, when I run this reverse it is very smooth sounding, no 'grinding' sounds at all. Another slightly subjective test was when I ran the tool at 1700 forward, after 5 min I could not touch the motor without burning my fingers . When I let it cool down, and did the same test in reverse, it was mildly warm, but not hot after a similar timeframe.

I'm going to get a motor replacement as it looks like it is not a controller issue.

[Al_The_Man]

This is the P.M. AC motor correct?
What can cause weird noise that at first appears to be mechanical is when the commutation firing is either not phased right, which should not be the case here as you have not changed the connections, and also something either in the motor halls or perhaps more likely a commutation fault in the drive giving false firing. Any of these can cause rapid heating of the motor.
Al.

[Joel779]

Not sure about PM AC motor. I thought these beasts used DC motors. There is def a 'mechanical' type noise if I try to restart the spindle in forward after it has 'jammed'. But I am not familiar enough to decide if it is a field 'freeze' for lack of a better term. This was one of my guesses, timing. But I don't have
anywhere near enough knowledge about these motor/driver combos to decide if this is electrical vs mechanical.


Anyway you look at it, things get noisy and toasty when running above 1200 RPM forwards, but not when running in reverse.