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Spindle current problem

ifixcnc

Hot Rolled
Joined
Feb 6, 2015
Location
Cleveland Ohio
Horizontal boring mill, gear head. The speeds that have the disturbance will over heat the spindle motor. Fanuc has been in on the problem, and swapped out the drive, and tried to tune the problem away, with no luck. Motor meggers OK? Any ideas?

hyund I chop grp1 3 copy.jpg

hyund sp mtr 1.jpg
 

ifixcnc

Hot Rolled
Joined
Feb 6, 2015
Location
Cleveland Ohio
Incoming power is fine.
The current to the machine shows the disturbance on all 3 legs.
The speed is steady, so the electronics are compensating for what ever this is?
 

Milland

Diamond
Joined
Jul 6, 2006
Location
Hillsboro, New Hampshire
Incoming power is fine.
I will amp clamp the incoming to see if it is being disturbed.
The speed is steady, so the electronics are compensating for what ever this is?

My knowledge of electronics and electrical isn't fantastic. If the power is fine, is there any chance that the motor megging didn't catch something that's still a problem? At elevated temperatures could insulation fail, but it works at room temp?

If you have access to a multi-channel storage scope and three induction probes, could you get readings from the drive to the motor itself? Is the motor unstable, or overcurrent alarming, or what?
 

ifixcnc

Hot Rolled
Joined
Feb 6, 2015
Location
Cleveland Ohio
I do not have a multi-channel storage scope and three induction probes.
The motor over heats (80C).
The problem only happens at certain motor speeds, above and below are fine.
The problem is exactly the same hot or cold.
 

Milland

Diamond
Joined
Jul 6, 2006
Location
Hillsboro, New Hampshire
I do not have a multi-channel storage scope and three induction probes.
The motor over heats (80C).
The problem only happens at certain motor speeds, above and below are fine.
The problem is exactly the same hot or cold.

Interesting - but it does point to the drive, not the motor, at least in my limited understanding.
 

Ziggy2

Stainless
Joined
Jun 22, 2013
Location
Northern Il
Horizontal boring mill, gear head. The speeds that have the disturbance will over heat the spindle motor. Fanuc has been in on the problem, and swapped out the drive, and tried to tune the problem away, with no luck. Motor meggers OK? Any ideas?

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I don't think your problem is electrical. FANUC swapped the drive and the problem still exists.

If it were a motor problem, it would likely be heat related and would not be cyclical in nature. More like a single event and somewhat random depending on the load.

I would be looking for a problem in the gear train between the spindle and the motor. Likely a bearing going bad or gear with a tooth chip in it or else the spindle.

Much to consistent to be an electrical/heat issue. Also the current would likely not be a sharp spike but rather a ramp up to peak.

Could also be the spindle brake is either toggling off for some reason. That you could see on the I/O display and or rack. Now that could be a bad wire that has an intermittent connection.
 

Milland

Diamond
Joined
Jul 6, 2006
Location
Hillsboro, New Hampshire
I would be looking for a problem in the gear train between the spindle and the motor. Likely a bearing going bad or gear with a tooth chip in it or else the spindle.

For a bearing to be bad enough to put enough drag on the motor to cause an overheat, but then get better at higher RPM doesn't seem reasonable.

Could also be the spindle brake is either toggling off for some reason. That you could see on the I/O display and or rack. Now that could be a bad wire that has an intermittent connection.

This is more interesting, but still seems unlikely. It might be a good test to track the temps of the braking resistors (if it has them) during operation in "proper" and "bad" operating speeds.
 

BT Fabrication

Stainless
Joined
Nov 3, 2019
how was the motor tested? need HV tester, a digital multimeter won't pick up certain issues like this
to me it sounds like a vibration that is causing a short/bad connection. wont see it unless under load.
 

Vancbiker

Diamond
Joined
Jan 5, 2014
Location
Vancouver, WA. USA
First thing I'd do is remove the motor or disconnect it from the load. Then run the motor at the speeds that are troublesome. If it runs OK then this points to mechanical issues. If it still overheats then I'd look at the speed feedback signal.
 

swarfmeister

Aluminum
Joined
Aug 29, 2017
Check all the physical connections from the power source to the motor. I had an air compressor that would pop the overload on the motor starter but the actual amps drawn were far less that what the overloads were rated at (measured each leg with an amprobe). What I found was that there was a little bit of arcing that had occurred between the motor starter and the modular overload, which would overstate the current to the overload unit. I replaced the overload with a new module set it up, and it's been trouble free ever since.
 

13engines

Hot Rolled
Joined
Jun 30, 2015
Location
Saint Paul
Some tidbits.

I 2nd the disconnect the load idea unless it's a nightmare to get at and do. Though running in neutral would be practically the same thing... to a point.

I'm sure I read somewhere back in my "I'm going to meg all my motors" days that Fanuc was not keen on high voltage meggers. Meaning 500 volt type might be better then 1000.

For a bearing to be bad enough to put enough drag on the motor to cause an overheat, but then get better at higher RPM doesn't seem reasonable.

A bearing going bad to the point of overloading a motor would also have some noise attached to it, which the OP has not mentioned. Though when these things go out over time they're harder to detect, because the operator slowly gets used to what is a deteriorating sound. Still, it's not uncommon for a gearbox to be quieter and under less self imposed load at higher rpms, because entire countershafts are likely dropping out of the gear/torque train. If that countershaft is losing its bearings well...could that be enough to bring the motor to overheat? You'd think the noise would run you out if that bad. Unless your hearing is sort of crap like mine. Or as I said, you got too used to it.
 

atex57

Hot Rolled
Joined
Sep 6, 2006
Location
SW Wisconsin
My question would be. Is the problem at a certain spindle speed or at a certain motor speed. Try a different speed in the gearbox. I think a couple of others have hinted at the same thing.

Ed.
 

13engines

Hot Rolled
Joined
Jun 30, 2015
Location
Saint Paul
It is a nightmare to get at and do, and no neutral.

How big is this boring mill anyway? :-)

I see you have a dual winding motor. There are possibly two big fat contactors involved in the changeover for that. Have you checked their contacts lately? Burned up contacts could be at least part of your problem.

I wish I knew more about this machine of yours. Looking up this motor I see it's your basic flange mount. When you say "gear head" do you mean reduction gear head? If you have a single, automated gear change-over point, one you can see and hear happen, it's likely you have something like a 4:1 reduction gear box. When you hear it shift into the high range, for all practical purposes you're power is now being transferred straight thru the main shaft and the reduction gears are out of the picture. So other then the motor bearings, there's only one other set of bearings to think about. That's it.

If your machine has multiple gear levers and you're changing out gears in both the high and low windings of the motor, then you can forget all I just said. In the case of multiple gear levers, there is probably a point between shifts that will allow free movement of the motor or spindle. Though without seeing anything, it would be hard to know if the motor was spinning free as if in neutral. Running the spindle with a gear lever or two in it's mid point might be a bit scary. I'll leave that up to the OP to decide if he has the nerve for that or not. A close look at the gearbox in your parts manual might show you what levers to move to isolate the motor shaft as much as possible.
 

ifixcnc

Hot Rolled
Joined
Feb 6, 2015
Location
Cleveland Ohio
Hyundai KH63G
630MM Pallets, X37" Y33" Z30"
There are two gear ranges, and Y Delta contactors. Connections are good.
The problem occurs at the same motor speed in both gear ranges.
This machine is only 2 years old.
We bought it new (AS IS) from an out of state dealer who had an cancellation.
 

markz528

Hot Rolled
Joined
Sep 25, 2012
Location
Cincinnati
This is not a motor insulation to ground issue. That is what a megger (is actually a DC high voltage insulation ground wall tester - megger is a company that makes these testers) checks.

That graph is telling you something. What is capturing and displaying this data? What is the y scale scaling and the x scale scaling?

The spikes looks quite periodic. That usually refers to a mechanical issue. If you have the data, the way to tell is if speed dips and load increase are in phase or out of phase. In phase indicates a drive issue and out of phase indicates mechanical issues. Periodic disturbances are usually mechanical but not always.

One reason I ask what the x scaling is so that we can figure the period and how it may relate to a mechanical equipment period. It is best to run a fft (fast fourier transform) to determine the actual periodic frequencies. Some oscilloscopes have the ability to do a fft otherwise you need some software.
 








 
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