Noise from lathe drive

[Niels AbildgaardParticipant @nielsabildgaard33719]

[Niels AbildgaardParticipant @nielsabildgaard33719]

Four or two pole?

[Niels AbildgaardParticipant @nielsabildgaard33719]

Somehow I cannot put text on when having linked a photo.

I need some advice.

Single phase 4 pole drive system of my WM250 lathe makes an awful noise and I want   60 to 1200 rpm spindle speed with a VFD.

I can either use a two pole motor and a 1 to 5 Poly v belt or a 1 to 2.5 SPZ belt .Both with a big disc diameter of 125mm.

What will make most noise and trouble?.

Edited By Niels Abildgaard on 01/02/2019 09:18:02

Edited By Niels Abildgaard on 01/02/2019 09:18:47

[Brian WoodParticipant @brianwood45127]

Niels,

I can't guess at what you mean by " an awful noise". Is it the usual heavy hum from a standard single phase motor? Try it with the belt off to see if you have that too tight. Judging if it is excessive is rather subjective.

Fitting the motor on bonded rubber mountings will reduce the motor noise transmitted through the foot plate into the machine

Your second point regarding spindle speed will not be helped by fitting a 2 pole single phase motor as you will be doubling the motor speed from 1425 rpm to 2850 rpm instead. That too will be a 'noisy' motor.

I am confused by your reference to vfd as well, those systems are not compatible with single phase motors and you would have to change the motor to the 3 phase unit that the vfd will drive.

Regards

Brian

[Niels AbildgaardParticipant @nielsabildgaard33719]

Hello Brian .

The choice for was to buy either a two pole 0.75kW or a four-pole three-phase.

I will go to my electro pusher and buy a 0.75kW four-pole .

Noise,as You point out,depends more on rpm than load or anything else.

Thank You for guiding.

A friend changed the original S7 sinle-phase to three and VFD.

He is not going back

[SillyOldDufferModerator @sillyoldduffer]

Posted by Niels Abildgaard on 01/02/2019 09:17:31:

…

I can either use a two pole motor and a 1 to 5 Poly v belt or a 1 to 2.5 SPZ belt .Both with a big disc diameter of 125mm.

What will make most noise and trouble?.

…

I have a WM280VF lathe – 1.5kW 3-phase motor with VFD, and a similar headstock layout to yours except the 280 has two pulley stages and two belts driving the spindle.

3-phase motors are quieter than single phase, but not by much. The motor is not the noisiest part of my lathe, motor noise being drowned out by other sources:

• A cooling fan on the motor that runs all the time allowing the VFD to turn the motor slowly without risk of overheating.
• A cheap computer-type fan on the VFD that runs all the time keeping the electronics cool. The VFD is silent, the cooling fan is noisy!
• The change gears are noisy. Carefully adjusting the gap between teeth much reduces the problem but the lathe is much quieter when they are disconnected.
• The lathe has a simple 3-speed gearbox – it too adds noise.
• The bearings aren't silent, the chuck stirs air at high speed, and cutting metal can be noisy!

The thing I miss most about my mini-lathe is how quiet it was! The bigger lathe is much more capable, but it makes about the same audio volume as my workshop radio. Not ear-defender loud, but the noise is an irritating hash and hiss rather than motor hum. A mini-lathe could be used indoors, a WM280 needs a workshop.

Removing the cooling fans would reduce the noise of my lathe considerably, but I'd rather have them. I don't think there's much to be done about the gears – they are made down to a price and break most of the rules needed for quiet running – not cut highly accurately, not accurately assembled, not suitably finished, not made of sound deadening materials, gear profiles not designed to reduce noise, not fully lubricated, and not fully enclosed.

Worth listening to your lathe to see where the noise is coming from – perhaps it is just the motor! A wooden rod used as a stethoscope is good for finding sources. I suspect switching to 3-phase + VFD won't reduce the noise much but don't be put off – 3-phase is better than 1-phase for other reasons.

Dave

[Jeff DaymanParticipant @jeffdayman43397]

Hi Niels,

If that is a piece of big steel pipe the lathe is sitting on, the pipe itself could be acting like a sound amplifier of the motor noise, vibrating like a bell. I'd try the lathe on a wood or angle iron bench to see if noise is reduced before spending $$$ on VFD or different motors to reduce noise. Just a thought.

[HopperParticipant @hopper]

Could it be that strange drum arrangement you have your lathe mounted on amplifies noise?

[Niels AbildgaardParticipant @nielsabildgaard33719]

Noise was more or less the same as in picture.Single phase motors are junk.

[Phil WhitleyParticipant @philwhitley94135]

Chinese single phase motors ARE junk, and known to be very noisy. My brother has a factory making aircraft covers, and the noisiest motor in the place is a chinese single phase sewing machine motor. Usual causes are balance, loose laminations, and poorly wound badly laid coils. British made single phase motors are almost completely silent by comparison!

[Niels AbildgaardParticipant @nielsabildgaard33719]

Posted by Phil Whitley on 01/02/2019 16:03:02:

Chinese single phase motors ARE junk, and known to be very noisy. My brother has a factory making aircraft covers, and the noisiest motor in the place is a chinese single phase sewing machine motor. Usual causes are balance, loose laminations, and poorly wound badly laid coils. British made single phase motors are almost completely silent by comparison!

It will be a three-phase ,four pole 0.75kW motor of noble origin(made in China most likely)

What VFD to go for?

[Howard LewisParticipant @howardlewis46836]

The bench on which you mount your lathe needs to be rigid, if only from the point of view of dimensional stability.

I would not expect to get consistent work from a lathe on a flimsy support.

Plain sheet steel is likely to radiate any slight noise and effectively amplify it. (Especially if any of the frequencies coincide with the natural frequency of any of the panels ). A panel with a natural frequency of 50 Hz, or 60 Hz in North America, could be a nightmare!

Sheet steel panels are often braced, or slightly dished (Look for shallow diagonals, pressed in), to stiffen the panel.

In extreme cases, to damp out sound, panels have been made as a sandwich, double skinned with a lead or rubber filling. At least one Lotus car had a firewall consisting of two sheets of Aluminium with a foam filling, for strength as well as sound deadening.

Either the panel can be isolated from the exciting forces, (such as rubber mountings) or tuned so that the resonant frequency is above or below the normal spectrum of human hearing..

Lets hope that the "horrid noise" is not failing bearings! Nothing is fouling anywhere is it? Pulleys, or belts on guards?

Howard

[Niels AbildgaardParticipant @nielsabildgaard33719]

Posted by Howard Lewis on 01/02/2019 16:15:54:

The bench on which you mount your lathe needs to be rigid, if only from the point of view of dimensional stability.

I would not expect to get consistent work from a lathe on a flimsy support.

 

 

Hello Howard

 

All my lathes are mounted on a piece of granite or diabas(dolerit).

The black tube is a piece 600/640mm PEHD tube.

Motor makes the noise and I want 60 to 1200 rpm by turning a potentiometer anyway.

My wish for advise was between two pole and four.

I try four first.

 

Edited By Niels Abildgaard on 01/02/2019 16:40:59

Edited By Niels Abildgaard on 01/02/2019 16:42:31

[Howard LewisParticipant @howardlewis46836]

Ah! A man after my own heart! That should not flex noticeably. If in doubt, make it like a brick mausoleum!

Four pole motor will be smoother than 2 pole. Three phase, dual voltage, will be ideal for VFD speed control.

Howard

[Dave HalfordParticipant @davehalford22513]

Niels, You might find the noise is caused by the sheet steel rear splashback drumming, it's quite a big sounding board.

That said I have just swapped out a 1980's 1/2hp 4.5A 1480rpm Brooke Crompton English motor for a modern 1hp 4.8A 1480rpm Belgian Javac EFF2 efficiency on my lathe and the noise level is greatly reduced along with the current. So the problem still could be a noisy motor.

[Ian S CParticipant @iansc]

Not all Chinese motors are rubbish, and not all British motors are perfect, it's more a case of what you can afford.

Ian S C

[JasonBModerator @jasonb]

Is noise your only critera for choosing between 2 pole and 4 pole?

As you want to run down to 60rpm I would be more interested in which of the two will give the better torque and which will be happier running at a very slow speed with regards to cooling as well as power, long running at 150rpm  motor speed won't be ideal.

The later model 250 and 280 lathes with inverters still have two belt ratios so that the motors can run somewhere in the power band.

Edited By JasonB on 02/02/2019 11:24:00

[Nick HulmeParticipant @nickhulme30114]

Double your motor power and go 4 pole, the increased power will deliver adequate torque at lower speeds than the less powerful motor can manage.
If you choose a good quality 4-pole you can safely run at up to 200% of rated 60hz speed as the rotor construction is close enough to the 2 pole version as makes no difference.
You'll likely cover all the speeds you need without ratio changes with such a set up.

Fitting an air filter to the end of the motor will reduce fan noise, just a simple affair with a few layers of mesh and open fabric still allows plenty of air flow with massively reduced noise.

[not done it yetParticipant @notdoneityet]

Posted by Nick Hulme on 02/02/2019 11:52:04:

Double your motor power and go 4 pole, the increased power will deliver adequate torque at lower speeds than the less powerful motor can manage.
If you choose a good quality 4-pole you can safely run at up to 200% of rated 60hz speed as the rotor construction is close enough to the 2 pole version as makes no difference.
You'll likely cover all the speeds you need without ratio changes with such a set up.

Fitting an air filter to the end of the motor will reduce fan noise, just a simple affair with a few layers of mesh and open fabric still allows plenty of air flow with massively reduced noise.

I would not be keen on doubling the power unless the drive belt rating was similarly increased (as well as the possibility of driving the machine beyond its design parameters), so perhaps altering the pulley ratios, to obtain full lathe speed at 200% motor speed might be better (although the motor efficiency would be reduced at that speed), or better still ratios selected to better fit the range required at somewhat less than 120Hz maximum.

Remembering, of course that doubling the motor speed will likely quadruple the power drawn by the motor cooling fan.

On that basis, a 30% increase in motor power would likely be my maximum, if that option was considered. The designers(?) of these machines would allow the machine a safety margin (one hopes) but not an extra 100% I would guess! Changes, such as this, require a fair modicum of thought before grabbing a figure out of thin air.

[Neil WyattModerator @neilwyatt]

Posted by Phil Whitley on 01/02/2019 16:03:02:

Chinese single phase motors ARE junk, and known to be very noisy.

Just because one cheap sewing machine motor is junk, are doesn't mean they all are.

The one in my grinder is whisper quiet (you can barely tell it's running) and the one in my bandsaw is considerably quieter than the running gear.

I would say they are both as quiet as my Hoover 0.5hp motor and quieter than the two fractional Hp Parvalux motors I've got.

That on my pillar drill makes little noise as well.

Neil

[Neil WyattModerator @neilwyatt]

Posted by not done it yet on 02/02/2019 12:20:05:

Posted by Nick Hulme on 02/02/2019 11:52:04:

Double your motor power and go 4 pole, the increased power will deliver adequate torque at lower speeds than the less powerful motor can manage.
If you choose a good quality 4-pole you can safely run at up to 200% of rated 60hz speed as the rotor construction is close enough to the 2 pole version as makes no difference.
You'll likely cover all the speeds you need without ratio changes with such a set up.

Fitting an air filter to the end of the motor will reduce fan noise, just a simple affair with a few layers of mesh and open fabric still allows plenty of air flow with massively reduced noise.

I would not be keen on doubling the power unless the drive belt rating was similarly increased (as well as the possibility of driving the machine beyond its design parameters), so perhaps altering the pulley ratios, to obtain full lathe speed at 200% motor speed might be better (although the motor efficiency would be reduced at that speed), or better still ratios selected to better fit the range required at somewhat less than 120Hz maximum.

Remembering, of course that doubling the motor speed will likely quadruple the power drawn by the motor cooling fan.

On that basis, a 30% increase in motor power would likely be my maximum, if that option was considered. The designers(?) of these machines would allow the machine a safety margin (one hopes) but not an extra 100% I would guess! Changes, such as this, require a fair modicum of thought before grabbing a figure out of thin air.

A well know seller of motors and drives pointed out a few things:

1 Don't forget all UK motors are rated for +20% (60Hz) as standard.

2 Going 30% above rated shouldn't do any harm to any motor i.e. ~78-80Hz.

3 Several of their customers report 100Hz works fine, but they don't recommend it as (a) you lose power to fan and inductive effects and (b) they don't have any control over the circumstances.

Neil

[Niels AbildgaardParticipant @nielsabildgaard33719]

Posted by JasonB on 02/02/2019 11:23:25:

Is noise your only critera for choosing between 2 pole and 4 pole?

As you want to run down to 60rpm I would be more interested in which of the two will give the better torque and which will be happier running at a very slow speed with regards to cooling as well as power, long running at 150rpm motor speed won't be ideal.

For a couple of years my Boxford had a 1.1kW 6 pole and I did a lot of single point threading at three Hz and with 2 to 3 reduction.

.Motor never smelled bad.

Single point threading uses very little power.

Many modern motors have a termistor inside that can inform inverter.

Wishlist to inverter:

single 230 feed and three times 230 out 0.75kW

Act on termistor signal from motor

Act on inverter fan so that it only run when inverter is getting hot,

Understandable manual

Aproximate .5meter between inverter and buttons

 

Can that be had within say 150£ ?

Edited By Niels Abildgaard on 02/02/2019 13:00:48

[SillyOldDufferModerator @sillyoldduffer]

Just wondering if there is any difference in smoothness between a 2-pole 3-phase motor and a 4-pole motor? In my mind 3-phase motors are arranged such that there is a continually varying and proportional potential difference across all the windings . The changing 3-phase voltages create a rotating magnetic field that the pole pair on the armature follows thus driving the axle.

Although the power of the spinning magnetic field produced by the stator windings isn't completely smooth throughout each rotation, it's not far off – certainly much better than what goes on inside a single-phase motor.

Adding another pole pair to the rotor will roughly halve the motor's speed and double the torque. But what difference, if any, do the extra poles make to the smoothness of rotation and the noise? Apart from some reduction in general racket simply because the 4-pole motor is slower.

My feeling is that choosing between 2 and 4-pole motors is mostly about matching rpm and torque, and cost, not improving smoothness. As 4-pole motors are more expensive, it might not be a good buy if the costly motor didn't reduce the noise much and you also had to modify the lathe's drive train to get the right rpm at the chuck, or to run it permanently at less favourable VFD settings.

I may be talking rubbish again! Happy to be put right and learn summat…

Dave

 

Edited By SillyOldDuffer on 02/02/2019 13:45:18

[Phil WhitleyParticipant @philwhitley94135]

Three phase motors are smoother, quieter, and more efficient than single phase. Having said that, a well made single phase motor should be quiet too. I do not base my "chinese motors are junk" on one motor, I base it on the fact that every chinese motor I have is much noisier than it should be, and when you strip one to try to improve it, you can immediately see why they are noisy. They are very poorly wound, and constructed, and most have loose laminations, or even loose stators, which are almost impossible to fix. The MAIN difference the number of poles makes is the syncronous speed. On 50Hz a 2 pole is about 2860 rpm, a four pole is 1440 rpm, a 6 pole 950, and an 8 pole, like the one on my Covmac, 700rpm. The best (`but not thee cheapest) way to solve the OP's problem is to go for three phase four pole, and use a VFD to alter the speed. I believe that a four pole three phase on a VFD will have better torque charicteristics when used below its design speed.But I am not that familiar with VFD's, as I have three phase in my workshop but one must always be careful not to run the lathe faster than its design speed, because you do so at your peril! What is sufficient lubrication at 1000rpm will not be sufficient for 2000rpm, and the noise from the gears might be a bit loud too!

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