Servo motor noise

[Hidden]

Hi folks, I installed a generic 750W servo motor (https://www.vevor.de/servomotor-c_11222/naehmaschine-servomotor-naehmotor-justierbar-befestigung-kupplungsmotor-750w-p_010611078687) on my Pfaff 545 H3 6/01 CLPMN a while ago, but it makes an irritating noise (I only found out it was the motor after presuming it was the machine itself and cleaning every part I could take off...).

Here's an example without the belt (it sounds louder in the video than it really is):

And here is the noise it makes with the (old) belt. New belt sounds roughly the same.

The noise I mean is the CHWUNKWUNKWUNKWUNKWUNK sound. I'm fine with a bit of a whirr from the motor, but this doesn't sound good.

Things I've already done:
- cleaned and lubricated the whole machine
- aligned the wheels of the motor and the machine
- tried a different (75mm) pulley instead of the 50mm pulley
- replaced the belt
- varied the belt tension

Alas, it still makes the noise. Does anyone know what could be the cause of this? I found this other thread but

but his videos are not available anymore, and there is no solution posted.

Thanks!

- Hidde

[MtlBiker]

Just a shot in the dark, but have you tried running the motor without the pulley attached to the shaft?  It's not unusual for a pulley to be out of round (not perfectly balanced) and that can cause quite a noise.  I ran into that myself about a year ago and became so convinced it was the motor that I ordered a new one.  Once I had it installed I was shocked to find the same noise was there.  And only by luck I found it was actually the out of round pulley.  I'd changed to a smaller motor pulley in order to slow the machine down and the one I got online wasn't perfect.  I ordered a replacement pulley from a dealer who knew about this issue and the new pulley was perfect... no more noise.

And I've now got a spare servo motor just waiting until I find a nice used machine with clutch motor.

 

[Hidden]

Thanks for that suggestion! I did run it without a pulley, sounds roughly the same (it sounds quieter in this video because I filmed it from farther away). I replaced the old clutch motor on the Pfaff with the servo, unfortunately the clutch motor's pulley doesn't fit on the shaft of the servo, or I would've tried that one. That one feels very solid. The pulleys that came with the servo motor feel very cheap. It makes the noise with both of them (75mm and 50mm). I may try ordering a new, better pulley!

 

[Northmount]

@Hidden  It sounds like electrical switching noise being amplified by the motor housing.  Sort of like a stepper motor/actuator which are a type of servo.

Some cordless drills sound similar, usually just not as loud.

[Gump]

I would suggest looking for a refund. That noise is mechanical, like the armature is out of round, and is hitting something inside the motor. I don't think it will cure itself until whatever is hitting breaks off or grinds away.

[Hidden]

Just took apart the servo, cleaned whatever I could and put it back together again. Same noise

One thing to note is that the sound you hear is in sync with the machine (one CHWUNK per stitch). I'm not sure if that matters.

[Northmount]

3 hours ago, Hidden said:

One thing to note is that the sound you hear is in sync with the machine (one CHWUNK per stitch). I'm not sure if that matters.

But you get the same sound whether it is driving the machine or not, so that would appear to be a misleader.

Check with the seller/manufacturer about the noise the motor makes.  Exchange it for another, same model and see if it makes the same noise.

[dikman]

Bearing noise?

[Hidden]

1 hour ago, Northmount said:

But you get the same sound whether it is driving the machine or not, so that would appear to be a misleader.

Check with the seller/manufacturer about the noise the motor makes.  Exchange it for another, same model and see if it makes the same noise.

The noise I mean is the noise you hear in the video with the belt attached. Not the whirring noise without the belt. That doesn’t bother me too much. Is the whirring also a red flag? I’m not sure what these things are supposed to sound like! Dead quiet?

[fibersport]

Is your belt too tight?  A sightly loose belt with help absorb shock and vibration.  How about a bad bearing in the motor?

[Dwight]

OK . . . go out into the shop . . . get the longest . . . skinniest screw driver you can find . . . 

OR . . . if you have something with a plastic handle and has a long hard rod coming out of it . .  .

Turn on the motor at it's slowest speed  . . . put the metal end of the screwdriver or whatever else you have . . . and put the handle end up to the little flap that covers your ear canal . . .  push that flap against your head . . . and listen.  

You want to stick the end of that screwdriver (or other tool) just above where the shaft comes out of the motor . . . and on the backside at the approximate same place.

In the Navy . . . this is how we tested every bearing on the ship . . . and how we found out if one was failing.  

I'm going to take a shot in the dark and say you have a good bearing . . . but it was not greased from the factory . . . something that happens from time to time . . .  and when they run dry . . .  they make a very similar sound.

Just wish I had a dollar for every bearing I've listened to since I started that back in 1964 . . . 

May God bless,

Dwight

Edited October 13, 2023 by Dwight

[RockyAussie]

9 hours ago, Hidden said:

Just took apart the servo, cleaned whatever I could and put it back together again. Same noise

One thing to note is that the sound you hear is in sync with the machine (one CHWUNK per stitch). I'm not sure if that matters.

I came across a servo that looks like that one recently doing the same thing. We ordered in a new motor to replace it but before doing that we took the motor off to see if we could find anything. I think there must be a magnet thing inside because when we gave it a shake to start with there was a rattle noise but then it stopped rattling. We thought well lets give it another try on the machine and it then went fine. Its been going strong now for maybe 3 months without any noise. Maybe the sudden stop they do sometimes shook the magnet loose, I don't know. He now has a backup motor if needed now but means he would have to drill some new table mounting holes etc which is why we tried the other old one first.

[Constabulary]

That sound IMO is not an issue. I have two JACK Servos with 750W and the earlier one is running since.... have to guess ... since 2014. They both make this sound. I´m not sure but I think more 750w motors make this sound than the 550w motors but I´m not 100% sure.

[Hidden]

I took apart the servo again this morning for cleaning, here's some pictures:

 

The rough patch on the axle is suspicious, but I don't know what causes it, as it isn't actually in contact with anything when the motor is assembled. It might not be a problem at all. The middle part is magnetic, which makes it a real pain to get any small metal bits off of it. I also found that rough spot on whatever you call the thing on the right ^, cleaned that up but then realized that it doesn't actually spin :') goes to show the machining on these things isn't particularly top notch, though. I also checked the bearings and they are lubricated, spin okay and don't make any noise.

Here's a picture of the 50mm pulley, it does sorta-kinda look off-center a little bit (especially the first pic)

However, more importantly, I just learned that these pulleys are supposed to use a 3L belt. The machine I bought came with an SPZ belt, which is the same width but taller. I bought an SPZ belt of the same size to replace it. The plastic part that can be screwed over the pulley also had some shavings of the old belt in it, which I found a little suspicious.

Guess I'll order a 3L belt to see if that works better, maybe a new 45 or 50mm pulley as well. Or a polyurethane belt. Thanks all for your help so far!

- Hidde

 

Edited October 13, 2023 by Hidden

[CowboyBob]

FWIW,Alot of the first servos we got in 15 yrs ago used to be pretty loud some in the same shipment were louder than others,they claimed it had something to do that they had uneven # of windings in the coils as time progressed they seemed to get quieter.We only use the brush type now & they all seem to be real quiet.

[kgg]

 

2 hours ago, Hidden said:

I took apart the servo again this morning for cleaning, here's some pictures:

I would send back the motor for a refund as the cover has damaged the bearing face as can be seen in your photo's. I would not accept a replacement as there is a problem with their cover mold and you are more then likely just going to have the same problem. The problem with keeping that motor is it will never run true and is going to fail, when who knows.

kgg

[Hidden]

1 hour ago, kgg said:

 

I would send back the motor for a refund as the cover has damaged the bearing face as can be seen in your photo's. I would not accept a replacement as there is a problem with their cover mold and you are more then likely just going to have the same problem. The problem with keeping that motor is it will never run true and is going to fail, when who knows.

kgg

Apologies, what is the bearing face? Is that one of my circled parts?

[kgg]

2 minutes ago, Hidden said:

Apologies, what is the bearing face? Is that one of my circled parts?

The circled part in photo #2.

kgg

[GerryR]

The circled part in photo #2 shouldn't be touching anything on the bearing.  The bearing sits in the machine bore in that housing.  If I was into the motor that far, I would remove that flash (lower circled part in photo #2) with a cutter of file.  Check the bearings while the rotor is out of the housing; they should be smooth as butter while applying some pressure on them as you rotate them.  If they feel "gritty" or there seems to be a "bump" while rotating, then it is a bearing problem, otherwise they are good to go.  The rough spot on the rotor shaft, top circled part in photo #2, isn't touching anything and should be of no concern.  Just my $0.02

[fibersport]

I agree that the circled part isn't the issue, that is what the bore of the bearing sits on, if the bearing is turning on that there's a big problem. Also, I don't think the flash on that end cap or end bell is causing it, look at the distance from the bearing to the armature.

[Northmount]

On 10/12/2023 at 6:16 PM, Dwight said:

OK . . . go out into the shop . . . get the longest . . . skinniest screw driver you can find . . . 

Rudimentary stethoscope, works very well.  Have used it in many cases, machinery in power and process plants, automotives, etc.  Works so well I bought a stethoscope (mechanical, not medical) and have used it a few times.  Screw driver is usually closer at hand so I often use it instead of going back to get the stethoscope.  A stethoscope helped me find a cracked/broken wrist pin in a old style Dodge 318 V-8.  Top side of the engine, noise was on front cylinder on right bank, on the bottom it was on the 3rd cylinder.  Cracked wrist pin was on the 2nd cylinder directly between the two measurement locations.  Replaced piston, wrist pin, rings, rod and gaskets, and was back on the road for about $80 in parts.

[Northmount]

2 hours ago, GerryR said:

Check the bearings while the rotor is out of the housing; they should be smooth as butter while applying some pressure on them as you rotate them.  If they feel "gritty" or there seems to be a "bump" while rotating, then it is a bearing problem, otherwise they are good to go. 

This bearing was cleaned and spun by the shop maintenance man/machinist.  Pronounced as good, no need to replace it.  I had done vibration sampling and found it to be 'noisy'.  Had the print out to show it.  Took the bearing away from him and cut it with an angle grinder.  This is what it looked like.

I had run vibration tests on the machine because it was literally screaming at 5000 RPM.  So don't trust that cleaning and spinning a bearing is an adequate measure of its health. 

Bearing on the opposite end of the shaft was the main culprit, but once you have the machine apart, replace the $10 bearing and save another 18 hours work in tear down and repair.

 

Bearing in the 2nd photo was causing the shaft to jamb during attempted startup, so he put a pipe wrench on the shaft to loosen it up.  A real no-no!  Half deaf so he didn't notice the machine screaming.  This was in a steam turbine lab in a technical school.  I could hear it from out in the hallway with the door closed.

 

[GerryR]

9 hours ago, fibersport said:

I agree that the circled part isn't the issue, that is what the bore of the bearing sits on, if the bearing is turning on that there's a big problem. Also, I don't think the flash on that end cap or end bell is causing it, look at the distance from the bearing to the armature.

I wasn't suggesting that the flash was causing the problem, but seeing that you had it apart, you might as well clean it up.  Also,  you might want to just replace the bearings as they are not very expensive and are probably stock items at McMaster-Carr Supply.  Another issue is that the rotor itself may be out of balance; from the rough machining that was done, it is a distinct possibility.  (I guess we know why a lot of the cheaper import stuff is less expensive; hit-and-miss on quality.)

[Hidden]

Been in contact with the store I bought the motor from (vevor.de), and look at this:

I replied I wanted a new motor or a full refund twice, looks like Pedro REALLY doesn't want me to return this thing (if Pedro is not a bot!). I found it quite amusing.

[AlZilla]

It doesn't make it with the belt off but does with the belt on. It's got to be a bearing. Take their 70 euros, replace the bearings and never buy another vevor product.