Noisy EMC Spindle ?

[northwestfab]

We have a 2005 Fadal EMC, when getting into the 6K+ RPM range, I can hear what I can only describe as ringing - sort of the ringing you'd get in your ears after a loud concert coming from the spindle. I cannot honestly recall if this has been on-going, but I am only noticing it recently, making me thing it is only recenty it started to occur.

We have 3 months of warranty left - is it time to get a tech over to look at the bearings ? could somthing else be the cause ?

Thanks for any input.

-Kyle.

[carbidecraters]

Its probly an idler bearing

[fpworks]

It doesn't have idler pulleys.

I think I know what you're talking about. Is it a cyclic sound, or is it constant?

[Geof]

Originally Posted by northwestfab ...We have 3 months of warranty left - is it time to get a tech over to look at the bearings ?....

Yes. I don't have Fadals but my policy is if you have warranty left you bug the hell out of them until whatever is bothering you is fixed. To me that is the whole idea of a warranty. Don't worry about what might be making the noise just tell them you want it to go away.

[NC Cams]

Welcome to the issues that high speed operation of a spindle can generate/uncover.

You could have a condition called "cage rattle". At high speeds, the cages of unpreloaded bearings or bearings that are slightly misaligned, albeit acceptably within the allowed specs, start to "rattle".

This occurs due to the cyclic speed up and slow downs that are natually occurring in non-DC motors or on acceptably misalighed bearings. The speed up/slow downs causes the cages to chuckle as the cages and/or balls crash into each other.

This phenomenon is not uncommon in pressed or machined metal cages, it does NOT tend to occur in/with moulded nylon cages. It is also highly cage design dependant. Some cages run on the ball C/L and these can rattle quite a bit. Land rinding cages which may or may not rattle about as readily as they are a bit more stable as they slide along the outer or inner ring.

Over time, however, the cage can rattle to the point that it crack and gets pounded out by the ball hammering. At that point, things get REAL expen$ive.

This is a good example of what happens when guys start to run spindles are high speed day in and day out. Guys think that it is easy to make/run spindles at high speed. That is hardly the case. Worse yet, the DIY crowd thinks that simply installing some magic bearing will make a spindle high speed ready/capable. Again, not hardly.

I'd get the service people in and keep them there until they properly diagnose and/or repair the machine. Don't be surprised if they claim it is "normal" - which it just might be (see above) although, in the long term, it could turn ugly.

[northwestfab]

Originally Posted by fpworks It doesn't have idler pulleys. I think I know what you're talking about. Is it a cyclic sound, or is it constant?

At high RPM its constant. at low RPM I'm getting a cyclic sound, and when it turns the spindle off at low rpm there is a quick 'whrr' that wasn't noticible before. Sounds bearing related to me.

-Kyle

[NC Cams]

This could be a stretch but it is not unrealistic.

We had a VFD on a bearing noise test spindle. For some reason, no matter what bearing you ran on it, if it had a metal cage, it would sing rhythymically. The technicians were rating any bearing they ran on it as "defective" or "noise sensitive" for this reason.

On a hunch, we took it to speed and then cut off the power and let it coast - dead quiet. Having run into the problem before with some 3 pole cheap PM DC motors (armature cogging) , I then tried some other experiments with cutting off the power at various speeds. Again, at speed, noise, with power cut off, stone quiet.

It turns out that the armatures of AC motors (or any for that matter) do not run at a perfectly constant angular velocity - they literally accelerate and decelerate thru each and ever revolution as the current flow rises and falls in the coil windings. The bearings can't help but "feel" these accelerations/decelerations as they go up and down in speed right along with the minutely instantaneously fluctuating speed of the armature.

Over time, the cages will loosen up and rattle about a bit. Depeding on the wear, grease and/or accel/decel rate of the armature, the noise/rattle can be worse or not. Amazingly, in our experiment, as soon as you cut power, the noise simply quit - the thing was then purely acting as a flywheel and the bearing drag loaded the cages in one direction and that's where they sat until the rotor stopped.

Turn power on, they'd be quite while the thing accelerated, let the rotor stabilize at speed, it would sing away. Vary the speed and so would the noise frequency. If you turned power back on, the noise would come - cut power, quiet.

That sort of ruined that machines viability for noise testing from that point on in my mind but the machine was someone else's sacred cow - as far as I know, they still do "noise testing" with the machine today. Go figure.

[fpworks]

Quite possible it is bearing related.

I thought the same in our case, but the dealer kept pushing me to the bottom of their priority list since the machine wasn't down.

I got tired of waiting so I traced our noise problem to the belt. First, the big nut that controls how the belt "rides" on the pulleys needed a SLIGHT adjustment. Secondly, the edge of the belt that rides on the flange of the pulleys needed to be cleaned. Don't laugh, but cleaning the edge of the belt with WD40 completely licked the problem.

Hasn't made a funny noise since.

If you need me to explain in more detail, give me a call...I'll PM my numbers.

Justin