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Spindle motor overheat, alarm 254 WTF?

Rapid_Tech

Aluminum
Joined
Oct 27, 2014
Location
Toronto
Hey guys,

I got alarm 254 (spindle motor overheat) on my 2006 vf4. Spindle motor fan is working, touching the motor by hand, it is barely above room temperature. Machine was running a small endmill when it first popped up, at maybe 10-12% load. Called the HFO and they say the sensor or the wiring could be the problem. They said you can pull the sensor out of the motor but I've been trying to pull it and it's not moving at all, looks to be the original wires. Anyone with some words of encouragement?
 
Go into your Diagnostics screen and look dead center at the Analog Inputs. What does the temperature say? How about the coolant level and DC voltage? You're looking to see if those all look normal and make sense. I nuked a Mocon board from cutting wood in the machine and then vacuuming out the dust. The spark went back up that spindle temp wire and zapped the converter circuit on the board. Those values were wandering all over the place.
 
There's no spindle temperature reading, only what looks to be microprocessor temp, but that's normal 77F. The other values are steady.
 
That temperature is your spindle. So if it says 77F the error should clear and it should work. Does it work at all and then trigger an alarm again later? Or is the alarm stuck on and the display still says 77F?

This page shows the location of the temp sensor in the motor's junction box. There's nothing but, that sensor and the cable going to the Mocon.

There is one other possibility but, lets hope that's not it. When was the last time you changed the backup battery? Are you having any other weird behaviors? There was a parameter that I remember had to be flipped as I was restoring a completely-lost processor board (battery). It also said there was a spindle overheat until it was fixed but, parameters shouldn't be flipping on their own so this is low likelihood.

Are you able to clear the alarm and get the machine running at all?
 
Oh it is, I always thought it was the processor temp since it had the mu symbol in it. The temperature reading remains the same even when it's giving the alarm. There's no rhyme or reason as to when it alarms and when it clears by pressing reset. The alarm can come on and I can hit reset 100 times in 5 minutes. Then the alarm might clear and I can use the machine for 30 seconds or 10 minutes before the alarm reappears.

I thought I'd check the sensor cable to see if that's the issue. It was wrapped really tightly around the motor so I cut one zip tie and let it have some slack. I though that had fixed it because the machine ran fine for about 30 minutes. All of a sudden, the alarm came back and I pressed reset another 50 times until I gave up and went home.

I did check the backup battery and it shows 3.2V and there are no other problems with the machine.
 
Sounds like a damaged wire to me. Blipping a wrong reading for a microsecond.

Does simply unplugging the sensor work? To would read zero but who cares.
you could always plug in another thermistor to the board. That way it has something to read, it would no longer read the motor but who cares
 
Whether you try to replace it or even unplug it to diagnose further, you have to dig into the processor triple-stack. The temp wire is top-center of the Mocon board (the last / bottom of the stack). I agree that it may work fine with that unplugged. If you haven't dug into the board stack before, pay careful attention, use a grounding wrist strap, etc. Everything is clearly labeled but, it doesn't hurt to take lots of phone pictures on your journey into it. Routing can sometimes seem like a mystery when you get everything out. Particularly a couple of the ribbon cables that go to and from the serial ports.
 
Finally home after a long 13 hour day and I have a little update for you gentlemen. The day started off with the machine alarming from the get go. Looking at the parameters, I noticed the "Cold Spindle Temperature" value was 100F. I don't remember if I changed it earlier but I put to 60. Alarm disappears, wonderful, let me get back to the job on the machine. Runs great for the next hour and a half and think the machine is fixed. Text a friend of mine that the machine is finally working properly. Five minutes later, alarm comes back, fu*k. The alarm now reappears almost as soon as I hit reset. Screw it, let me shut off the machine for a few minutes. Start it back up and the alarm is on right away.

I unplugged the sensor but it didn't make any difference. Came back a few hours later and started going through the parameters again. Found one called "spindle overtemp N/C" that was set to 0. Changed it to a one and the alarm is gone. Ran it for the next two hours without an issue. I'll see tomorrow if the alarm will still be off. Fingers crossed for now.
 
You unplugged the sensor from the harness or from the board? My suspicion is the harness is damaged somewhere and has a short. I might be mistaken on the display temp showing on Parameters being the spindle. Maybe it has another sensor somewhere.

If you dig through the parameters, there is one of those Overtemp NC for each axis. What I'm pretty sure that does is select if the axis has a normally open or normally closed thermal switch. If it has no switch or if the switch is normally open, that should be zero. If your spindle harness is shorted, all changing the parameter did was say, "no, no this is normal, your switch is normally closed." My factory settings show that as a zero for the spindle. Check it against your own book.

The other temp you changed from 100 to 60 is the setting for when it says "Your machine is cold and if you don't warm it up and feed it hot cocoa, it will smash all your parts forever more." 3 days and 60 degrees is what mine shows (late 2004).
 
I unplugged the sensor at the connector behind the spindle, before it goes into the caterpillar tray. I don't trust myself enough to start digging around the Mocon boards. I'm pretty sure the temperature displayed in the parameter page is for the microprocessor. It doesn't change as much as you might expect from a spindle. It'll start at room temperature at startup and only increase 5-8F after a while.

I'll see how the machine runs later today when I go in.
 
You unplugged the sensor from the harness or from the board? My suspicion is the harness is damaged somewhere and has a short. I might be mistaken on the display temp showing on Parameters being the spindle. Maybe it has another sensor somewhere.

If you dig through the parameters, there is one of those Overtemp NC for each axis. What I'm pretty sure that does is select if the axis has a normally open or normally closed thermal switch. If it has no switch or if the switch is normally open, that should be zero. If your spindle harness is shorted, all changing the parameter did was say, "no, no this is normal, your switch is normally closed." My factory settings show that as a zero for the spindle. Check it against your own book.

The other temp you changed from 100 to 60 is the setting for when it says "Your machine is cold and if you don't warm it up and feed it hot cocoa, it will smash all your parts forever more." 3 days and 60 degrees is what mine shows (late 2004).
I doubt it is a simple “on/off”
Electric motors typically use thermistor’s.
These vary resistance based on temp
This is read by the controller to say what the temp is.
Due to their size they are the most common temp sensor in electric motors and can easily be embedded into the winding


But I digress

Unplug it and try.
And yes. Use a grounding strap if your gonna play around. It’s a very cheap insurance policy.
 
I unplugged the sensor at the connector behind the spindle, before it goes into the caterpillar tray.
Yeah, that's why we suspect it's a pinched wire. If you have a momentary short, the NO/NC toggle in software will just flip behavior except now it will happen when the wire opens instead of shorts.

I doubt it is a simple “on/off”
Electric motors typically use thermistor’s.
I hear you loud and clear but, having a NO/NC toggle in the software would only work for a switch. Haas included it. Maybe it has both a temperature and an overheat switch.
 
I'm beginning to suspect I've got bigger problems than a pinched wire. I was running the machine without issue today and after 2 hours, I get an alarm, but this time it isn't for spindle overheat. The alarm was 237, spindle following error. I hit reset, bring the head to home position and try running the spindle again. I input S500 into MDI and all I get is maybe 30-50 rpm with the spindle load meter maxed out. I shut off the machine for a few minutes and restart, everything is normal again. I restart the program where I left off and after a few minutes I get the same alarm. I could understand if I had an old spindle encoder that was on the way out but I just changed it a few months ago when the same error came up.
 
Quick update, machine ran fine with no alarms Monday and Tuesday. On Wednesday evening, alarm 254 popped up again. I went into the parameters and switched "Spindle Overtemp is N/C". This was the parameter I changed on the weekend that cleared the alarm and now I changed it back to what it was before. Machine ran fine like this for the next 2 hours before I left.
 








 
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