Nakamura lathe spindle motor temperature

I recently found on my Nakamura WT-150 with Fanuc 18i-TB control that diagnostic #400 shows the temps of the four spindle motors (2 turning and 2 milling). I've been monitoring them, and the main turning motor seems to be getting really hot. The last two days of production, I've seen it get into the mid-90s Celsius area. It's been warm in the shop, but this seems excessive. Can anyone tell me if this is normal or if there might be a problem? It sounds fine, and the fan on the motor is pushing air, so I'm not sure what the problem could be if there was one. The spindle is doing probably half it's time turning and the other half milling. The turning being done is not heavy cutting. It's only working on 15/16" diameter bar. If anyone else has a lathe that shows spindle motor temp, could you let me know what temps you're seeing after running all day? Thanks!

Correction: The diagnostic numbers are 403 and 404. 403 is for the turning spindle and 404 is for the milling spindle.

Dont fix whats not broke. Motors do get hot. Can you put your hand on it? If fan is working, and machine is working ok I wouldnt worry about it.

We see about 35-50 degrees centigrade during normal operation. Our machines alarm out if any servo motor reaches 100 and I believe the warnings start at 80. I would definitely be looking into the cause of a motor constantly running 90*. We have only had them get that hot when there was a significant issue. The one I can remember right now was one of the two ball screws on an axis fell apart and the remaining servo had to handle the whole load. It could do it, but struggled.

Do you have any way to see the loading on the servos?

I checked the servos and spindle motors on my Nakamura TW-10 at the end of the day with a hand held thermometer and every thing is under 35C. 90C sounds really hot.
Something is going on here. Have you checked if the controller temps vs a hand held corroborate?

mmurray70 said:

Dont fix whats not broke. Motors do get hot. Can you put your hand on it? If fan is working, and machine is working ok I wouldnt worry about it.

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I’m a huge proponent of not fixing what’s not broke, but something seems off here. I can’t hold my hand on it for more than a moment. It’s hot.

J Gilles said:

We see about 35-50 degrees centigrade during normal operation. Our machines alarm out if any servo motor reaches 100 and I believe the warnings start at 80. I would definitely be looking into the cause of a motor constantly running 90*. We have only had them get that hot when there was a significant issue. The one I can remember right now was one of the two ball screws on an axis fell apart and the remaining servo had to handle the whole load. It could do it, but struggled.

Do you have any way to see the loading on the servos?

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I saw temps of 96 C today and no alarms. Maybe if it hits 100, it’ll alarm out. I feel like a really hot day in the shop, and I’ll find out. The load meters aren’t showing anything that’s out of the ordinary.

NASTYZEN said:

I checked the servos and spindle motors on my Nakamura TW-10 at the end of the day with a hand held thermometer and every thing is under 35C. 90C sounds really hot.
Something is going on here. Have you checked if the controller temps vs a hand held corroborate?

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I checked with an IR thermometer on the motor housing and was getting a max temp of 82 C while the diagnostic was showing 92. I’d say that those two temps are close enough to corroborate.

I checked some of the other machines, and the highest temp I saw was 68 C. The other turning spindle of this machine is only at 48. I’m really not doing any turning with this second spindle, though, other than grabbing the part when it gets cut off.

Something kind of weird that I did notice is that the temperature fluctuates with the machining cycle. The part I’m making has a cycle time of about 3.5 minutes. About the first half of that time is turning, then the rest is milling, cross drilling, cross tapping, etc. When the milling starts, the temperature starts creeping up. Then, once it goes back to turning, the temp drops. Today, for example, I watched it go up to 96 for the milling, then drop down to 92 for the turning. It does this repeatedly for every cycle. I don’t know how much of a lag between the heating of the motor and the reading of the temp sensor there is, so I can’t say for sure if it’s really the milling that causes more heat on the motor than the turning.

Like I said, the motor fan is working. I’m wondering if the vents through the motor housing might be clogged.

By the way, it seems that machines with Fanuc 18i-TB and 21i-TB (and probably newer) have these temp diagnostics if anyone else is interested in monitoring their machines. It seems like it could be a good preventative maintenance tool. 18i-TA and older don’t seem to have it.

I would go out on a limb and say that motors will produce more heat doing duty as a servo (c axis mode) than as a motor (spindle mode) so I'm not that surprised that it's hotter doing the milling than the turning.

if it's too hot only Fanuc can answer, but I guess if it was then you would get an alarm!

wmpy said:

.......Like I said, the motor fan is working. I’m wondering if the vents through the motor housing might be clogged...........

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I’ve seen the cooling passages in motors get gunked up so it’s worth looking at.

Is the spindle motor used as a servo when milling (Fanuc Cs function) or a separate servo? I’m thinking it is Cs. When the spindle motor is used as a servo there is a fair amount of current flow when holding a position. Current makes heat.

Have you amp clamped the motor legs? Have you megger checked the motor? Both those checks will be needed if you find no problem with the cooling system. Another thing to check is that there are no restrictions for air to reach the motor area.

Vancbiker said:

I’ve seen the cooling passages in motors get gunked up so it’s worth looking at.

Is the spindle motor used as a servo when milling (Fanuc Cs function) or a separate servo? I’m thinking it is Cs. When the spindle motor is used as a servo there is a fair amount of current flow when holding a position. Current makes heat.

Have you amp clamped the motor legs? Have you megger checked the motor? Both those checks will be needed if you find no problem with the cooling system. Another thing to check is that there are no restrictions for air to reach the motor area.

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Yes, the spindle motor is used as the servo when milling. There is no separate servo motor that gets engaged. I had the idea that maybe I forgot to program the brake to turn on for the operation where I do a lot of Y-axis milling, and the motor was heating up while trying to hold position instead of the brake. I checked the program, though, and the brake is programmed to come on for that op.

I haven't checked the motor with a megger. I can do that. I don't own and have never used an amp clamp. Maybe it's time for that to change. What would I be looking for? I still need to check out the cooling passages. It's a bit of a job to get at the motor, and I have to make another 1000 pcs or so before I can comfortably tear into the machine.

An easy check is to get your machine warmed up then run your program without stock and watch the temperatures. If you see the same temperatures, seems likely you have an issue with your stator or motor drive. If the cycle runs with lower temps, then likely a lack of cooling.