Spindle noise

[Eyecon]

Hello All,
My PM728 spindle recently started making high frequency screeching noise that mainly happens at speeds above 2000 RPM but recently also at lower RPMs. The sound is not coming from the belt or motor (disconnected and replaced the belt with a brand new one to isolate the sound) and PM tech support are telling me this doesn’t sound like the bearings. Wanted to get a second opinion because it does sound like a bearing issue to me. Video linked below:

 

[David]

I hear a slight rattling but no screeching.

 

[Eyecon]

I hear a slight rattling but no screeching.

Do you hear a high frequency noise that sounds like a worn alternator belt on an old car?

 

[David]

A little bit maybe but nothing alarming. To me anyway.

 

[Eyecon]

It’s very loud and very annoying to me at least 🙂
Can angular contact bearings make this sort of squeaking high pitch noise if they are worn or improperly setup?

 

[whydontu]

A harmonics issue at a specific rpm? Odd that the squeal reduces in volume at higher rpm.

 

[Eyecon]

A harmonics issue at a specific rpm? Odd that the squeal reduces in volume at higher rpm.

I think it gets drowned out by the motor and belt noise (the anti-clipping in the phone’s recording software)…just a byproduct of recoding the sound on the phone.

It shows up randomly at various low rpms as well with no specifics, the warmer the spindle gets, the more I hear it.

 

[whydontu]

Shot of oil into the quill bearings - if the noise changes, you know the problem.

 

[Mike R]

It’s very loud and very annoying to me at least
Can angular contact bearings make this sort of squeaking high pitch noise if they are worn or improperly setup?

Yeah, I hear that screetch, not normal for sure.
Looking at the exploded diagram, there is only 1 angular contact (#42 - a 7007) and there are 4 regular deep groove ball bearings - items 8, 11 (x2) and 39.
My bet is a skidding ball in a bearing, and as they are all sealed / shielded (ZZ) its going to be hard to get any lube into them.


You could try dropping the quill, may give some access to lube the one angular contact, and maybe check for tightness in rotation or slop in either end of the quill.

 

[David]

Changing bearings in these mills is a real PITA.

 

[Susquatch]

A harmonics issue at a specific rpm? Odd that the squeal reduces in volume at higher rpm.

It's prolly not the volume going down. More likely a hearing problem.

Happens to me with all high frequency sounds. I don't hear my wife unless I can see her lips move. But I hear all 3 of my sons just fine.

 

[jcdammeyer]

Hello All,
My PM728 spindle recently started making high frequency screeching noise that mainly happens at speeds above 2000 RPM but recently also at lower RPMs. The sound is not coming from the belt or motor (disconnected and replaced the belt with a brand new one to isolate the sound) and PM tech support are telling me this doesn’t sound like the bearings. Wanted to get a second opinion because it does sound like a bearing issue to me. Video linked below:

I hear the screeching when I use YouTube to play the video. To me that would be quite painful if I'm wearing my hearing aids.

I agree, some oil into the bearings to see if it diminishes or goes away. Alternatively a different VFD controller on the motor since it's very RPM dependent. If it goes away you know it's the controller.

 

[Eyecon]

Thanks everyone for the suggestions. I narrowed down the sound to the top spindle sleeve bearing (#8 in the diagram above) because after spraying a little bit of WD40 the sound went away…trouble is it only goes away for a few minutes and then comes back. Any suggestions on how to properly lubricate this type of bearing or should I try and get it replaced?

 

[jcdammeyer]

Thanks everyone for the suggestions. I narrowed down the sound to the top spindle sleeve bearing (#8 in the diagram above) because after spraying a little bit of WD40 the sound went away…trouble is it only goes away for a few minutes and then comes back. Any suggestions on how to properly lubricate this type of bearing or should I try and get it replaced?

If it's not sealed you can always just pour in something dramatically thicker than WD40. Or pull it and grease it ala wheel bearing style to force grease into it. If it's sealed then replace it.

 

[David]

Almost 100% chance that it's a sealed bearing unfortunately. And pulling the bearings on these machines is a bit of a trick.
There are loads of videos out there showing how to do it

 

[Mike R]

If its screeching its done, kaput, gone, TU, etc. No coming back. etc...
Don't waste time with it, lubing it will just make you think you fixed it until it fully seizes on you or gets so loose the balls fall out.
I mean, I would also probably lube it too to keep it going if I needed to, but my logical side says its already damaged and just going to get worse. May as well bite the bullet.
When changing it, try to take measurements of the shaft its going on. Often a failure like this is precipitated by the bearing being fit onto an oversize shaft, or pressed into an undersize hole.
That bearing is cheap. You could probably replace with 6209 2RS instead (rubber seals vs the metal shield ZZ type) - limited to 5K rpm - which I understand is above the rated speed of that spindle (4K)?

 

[Mcgyver]

What Mike said. Go with SKF or other reputable make and another vote for 2RS bearings. Unless there is a speed issue, all shielded or sealed bearings in my shop get replaced with 2RS (low friction sealed).

If you are not sure how install bearings ask, and if you have to pull one to get at the offender, replace it to. Generally pulling them destroys them (damages or brinnels the high precision internal surfaces which is the beginning of the the end)

 

[Eyecon]

Thanks all for the suggestions, I will replace that noisy bearing but that will require a full disassembly of the head. I'll just use a heavier oil to dampen the noise for now until I obtain the replacement bearing.


On a related note: I think I got some WD-40 into the bottom 7007 angular contact bearing in my attempt to locate the source of the noise.So far everything seems to be running fine (not heating, no noise from that bottom bearing...) but I likely compromised the grease in that bearing. I have some NBU 15 grease, should I just reapply or do I have to flush the grease out of the bearing completely (with kerosene), dry and re-grease? I never had to re-grease an open bearing but done it a bunch of times on new ones.

 

[Proxule]

but I likely compromised the grease in that bearing.

Absolutely

I have some NBU 15 grease,

Atta boy!! Remember, not too much. 30% or less. Especially on high speed applications. YMMV

should I just reapply or do I have to flush the grease out of the bearing completely (with kerosene), dry and re-grease?

If its a RR or similar seal you can pry off easily, Then yes absolutely flush and clean and repack. Especially if its an open bearing. I use varsol and and small painters brush. Never use compressed air to spin up the dry bearing. Alcohol or brake clean after wards and some compressed air on low PSI. Dont let the races spin up.

Gluck

 

[Eyecon]

Absolutely

Atta boy!! Remember, not too much. 30% or less. Especially on high speed applications. YMMV

If its a RR or similar seal you can pry off easily, Then yes absolutely flush and clean and repack. Especially if its an open bearing. I use varsol and and small painters brush. Never use compressed air to spin up the dry bearing. Alcohol or brake clean after wards and some compressed air on low PSI. Dont let the races spin up.

Gluck

from what I can see, the bearings are completely open, there's a removable plastic cap at the bottom of the spindle that provides access...that cap was leaking a bit of WD40 which is how I figured that it go into the bearing. I'll use a small acid brush and mineral spirits to get all the old grease out and clean with alcohol and then reapply grease using a blunt tip needle and syringe. Specs I found from SKF indicate about 2 cm3 or about 2 grams of grease is standard for this bearing which I guess should be about 20-30% of the volume.