chinese 2kW spindle motor repair

Hi, I have a relatively new chinese 2kW, water-cooled spindle motor which has developed a bearing squeak. It is also drawing air in over night every time I use it.

By adding an low pressure air line to the water circuit ( having eliminated the pump and heat-exchanger ), I have determined that there is an air leak in the motor. I suspect this also means that there is a water leak and that this may be the origin of the bearing problem.

The motor probably has something like 10h of service time , though I purchased it about 3y ago so cannot return against the supplier.

It worked fine until recently when I started to notice an intermittent slightly dry sounding squeak when running. It definitely sounds like a dry/worn bearing.

The supplier claimed they used German made bearings , we'll see whether that is true.

Does anyone have any experience/tips/info on stripping down these motors?

Thanks.

For information, this looks identical , though it is not the actual supplier I used.
https://www.aliexpress.com/item/32846880341.html

There are several threads here showing disassembly. Try searching for them.
The bearings are not German made, but can be replaced fairly easily, if you can get the spindle apart. You'll need a pin wrench for the nut on the nose, and the top nut under the cap is left handed.

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Originally Posted by reg.miller

Hi, I have a relatively new chinese 2kW, water-cooled spindle motor which has developed a bearing squeak. It is also drawing air in over night every time I use it.

By adding an low pressure air line to the water circuit ( having eliminated the pump and heat-exchanger ), I have determined that there is an air leak in the motor. I suspect this also means that there is a water leak and that this may be the origin of the bearing problem.

The motor probably has something like 10h of service time , though I purchased it about 3y ago so cannot return against the supplier.

It worked fine until recently when I started to notice an intermittent slightly dry sounding squeak when running. It definitely sounds like a dry/worn bearing.

The supplier claimed they used German made bearings , we'll see whether that is true.

Does anyone have any experience/tips/info on stripping down these motors?

Thanks.

For information, this looks identical , though it is not the actual supplier I used.
https://www.aliexpress.com/item/32846880341.html

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The only normal place they leak is in the top cap where there are 2 orings air pressure may not of been a good idea as it would be a much higher pressure than the water would ever be so could pass the orings quite easy if they have got hard or not sealing with enough compression

Did you use anti freeze or anti-corrosion in the water to protect the aluminum motor core, it will corrode badly if you did not, and have seen them eat right through the water jacket

German Bearing is just a sales gamic, they could well be German made Bearings as most German made Bearings are made in China

As for returning your spindle that is not an option even if it was new, it would cost you more to ship it back than to buy a new one

Are they repairable depends if the water has done any damage in the winding area or not

To disassemble you need the correct wrenches to disassemble any of the moving parts, if you damage any of them then the balance of the spindle will be affected and then is basically junk unless you can balance any new parts needed

Thanks, I did find a U-tube vid but did not pick up the LH thread. That could have caused me some head-aches, so thanks for the tip. I did see I need a pin wrench, not sure where I can find that. It looks like I need to get the end good and hot to loosen it too. Maybe some thread locking adhesive on there too.

This supplier, like the one I ordered from does claim to use german bearings, whether that is a truthful claim or not remains to be seen. I doubt they are all lying. Many make no claims and are obviously using low quality chinese junk which probably have excessive run-out and will not last.

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Originally Posted by mactec54

The only normal place they leak is in the top cap where there are 2 orings air pressure may not of been a good idea as it would be a much higher pressure than the water would ever be so could pass the orings quite easy if they have got hard or not sealing with enough compression

Did you use anti freeze or anti-corrosion in the water to protect the aluminum motor core, it will corrode badly if you did not, and have seen them eat right through the water jacket

German Bearing is just a sales gamic, they could well be German made Bearings as most German made Bearings are made in China

As for returning your spindle that is not an option even if it was new, it would cost you more to ship it back than to buy a new one

Are they repairable depends if the water has done any damage in the winding area or not

To disassemble you need the correct wrenches to disassemble any of the moving parts, if you damage any of them then the balance of the spindle will be affected and then is basically junk unless you can balance any new parts needed

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Thanks Mac. I'm suspecting poor sealing at the top. I was not sure before what the water ways went inside. It seems they just go round the jacket. I did not use any anti-freeze but it has not been running under water that long. No signs of corrosion. Once I get it water-tight, I'll look into what it needs. Is standard automotive radiator fluid OK?

The compressor pressure was very low when I pressurised, to I don't think I blew anything. It was already leaking , which is why I was pressure testing. I put soapy water around the pipe fittings and no bubbles, so the air leak must be inside. The top came off without any effort. I suspect it was not properly sealed.


Others have mentioned counterfeit bearings. I know asians have no compunction about marking whatever you would like to see on your product. They could also be second class items which fail the QA controls when making genuine "german" parts. Once I bought Bosch brakes for my van which on inspection were obviously made by hand is some 3rd world sweatshop. I checked with Bosch as to whether they counterfeit but they actually owned up that they were real. I sent them back and bought another marque.


Your point about balancing if very pertinent. That's why I'd hesitated to open it up until now. But I had the machine stripped down and it seemed like a good time to investigate the squeak. Now I need to make a pin wrench.

Even if german bearings are made in China, they need to maintain QA standards. I've had lots of chinese bearings which are not round and not centred. That would be a big issue at 24000 rpm.

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Originally Posted by reg.miller

Even if german bearings are made in China, they need to maintain QA standards. I've had lots of chinese bearings which are not round and not centred. That would be a big issue at 24000 rpm.

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You don't have to worry about the Bearings being bad quality I have never seen this in any of these Spindle repairs I have done, a spindle that cheap $120 is a cheap buy and not worth your time to take it apart, the same replacement bearing could cost you more than that, unless you can get them from China which is ok to do

On the cheapest spindles though I have seen regular deep grove Bearings which are no good for a spindle like this, so if it has regular Deep Grove Bearings then it is junk, most all have sealed Ac Bearings though

The top nut on the end of the spindle is left hand and some times has Loctite on the thread, make sure there is enough compression on the 2 Orings or they will leak

You have to take care when taking the rotor out as there are preload Belleville washers at the top that you don't want to get them orientated the wrong way so take note for reassembly, some have springs which are different way they do the preload for the Bearings

I decided to go no further to avoid disturbing a finely tuned machine and trying to set it up correctly when rebuilding without full info I like torque on bearings.

All I did so far was to remove the top cap where the water inlet/outlet is and lightly grease the O-rings to ensure no air leaks. I also unscrewed the four retaining screws on the lower ring but when it did not come off I put them back.

However, now when I start the motor it trips the 30mA differential. I am assuming that there is some water in the motor somewhere it should not be.

Does anyone have any info/photos on where the water ways go in the jacket? Some excellent threads on stripped motor but I don't see detail of the water ways.

Any help on that would be appreciated. Thx.

Quote:

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Originally Posted by reg.miller

I decided to go no further to avoid disturbing a finely tuned machine and trying to set it up correctly when rebuilding without full info I like torque on bearings.

All I did so far was to remove the top cap where the water inlet/outlet is and lightly grease the O-rings to ensure no air leaks. I also unscrewed the four retaining screws on the lower ring but when it did not come off I put them back.

However, now when I start the motor it trips the 30mA differential. I am assuming that there is some water in the motor somewhere it should not be.

Does anyone have any info/photos on where the water ways go in the jacket? Some excellent threads on stripped motor but I don't see detail of the water ways.

Any help on that would be appreciated. Thx.

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You can't see the water ways the outer Stainless Steel Tube is pressed over the top of the body, so you can not take that apart without destroying the spindle, you most likely got water in the spindle when you took it apart ( Top off ) you have to blow the water jacket out before you take them apart or water will get inside

Take the top back off first blow the water out of the jacket remove the top Nut / Bolt ( Left Hand Thread ) undo the front screws, and with a soft bar aluminum press or what ever way you are comfortable with, from the top on the end of the motor shaft ( in the center of the Bearing )

This will remove the Rotor as a complete assembly, then you can see if there are any leaks and dry out the windings

Thanks, I'm a little doubtful that the water has got past the plastic sheet screwed into the top , mounted with Si sealant and through the sealed bearing ( plastic seal type ) at the top. I'm considering the possibility of a porous casting of the Al body.

I'm now guessing that the water-ways are cut into the outer surface of the ali body and closed by the s/s sleeve, so that there is only the inlet/outlet that we see at the top. Is that consistent with your understanding?

When you speak of the front screws, I see one plate with four screws which does not come off directly and another part with four screws which seems to house the two bottom bearings.

Since the first ring obscures access to the retaining screws of the bearing block, it seems that I need to remove the ali lock ring which is torque fitted on to the bearings to gain access to the bottom bearing block fixation screws before I can chase out the rotor. Is that correct?

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I'm now guessing that the water-ways are cut into the outer surface of the ali body and closed by the s/s sleeve, so that there is only the inlet/outlet that we see at the top. Is that consistent with your understanding?

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Basically, yes. I've seen one picture of a motor with the outer sleeve removed, but not sure where I saw it.

Quote:

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Originally Posted by reg.miller

Thanks, I'm a little doubtful that the water has got past the plastic sheet screwed into the top , mounted with Si sealant and through the sealed bearing ( plastic seal type ) at the top. I'm considering the possibility of a porous casting of the Al body.

I'm now guessing that the water-ways are cut into the outer surface of the ali body and closed by the s/s sleeve, so that there is only the inlet/outlet that we see at the top. Is that consistent with your understanding?

When you speak of the front screws, I see one plate with four screws which does not come off directly and another part with four screws which seems to house the two bottom bearings.

Since the first ring obscures access to the retaining screws of the bearing block, it seems that I need to remove the ali lock ring which is torque fitted on to the bearings to gain access to the bottom bearing block fixation screws before I can chase out the rotor. Is that correct?

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It is possible that the aluminum housing has sprung a leak, it has happened before, the water ways are cast into the aluminum housing and just the OD is machined to suit the SS Tube

The bottom Plate with the 4 Cap Screws that you can just get at, you can undo them as far as you can push out from the top of the spindle and then undo the cap Screws some more it can all come out as one piece and you don't have to remove the Aluminum Bearing locking nut on the front, if you have the correct wrench to undo this it will just make it easier to get the 4 capscrews out

The Top Bearing will stay in the Housing and comes out through the top if needed to be removed

So under the Plastic cover remove the center Bolt ( Left Hand Thread ) and the front plate 4 capscrews and push out from the top on the shaft where you removed the Bolt

Don't worry about the torque for the front Nut if you have to remove it, it is just done up tight like 60 Ft Lbs max

Many thanks, it's invaluable having someone who knows what these things are like inside.

I had to drill a small hole in the guard ring to get clear access to allen screws behind it and have been able to slacken by about a mm as you suggested. However, this model does not have the LHT bolt on the top , it has an ali ringnut with very small spigot holes . It looks like the ring on the bottom but a lot smaller. In view of the recessed position I won't even be able to get a pin-wrench on there, I'll have to make a more complex tool. I can see this ending with a hammer and chisel and me looking around for large, fine threaded LH tap !!

I'm going to try drying this out in the oven. I pre-heated the oven to 95 deg C ( IR thermometer ) , cut the gas and put the body in. I'll let it sweat it out for a while.

IIRC the operating temp is spec'd for about 80 degrees. I guess the Achille's heel is the plastic seals and guard-rings. The winding's varnish should resist a lot higher than that.

Quote:

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Originally Posted by reg.miller

Many thanks, it's invaluable having someone who knows what these things are like inside.

I had to drill a small hole in the guard ring to get clear access to allen screws behind it and have been able to slacken by about a mm as you suggested. However, this model does not have the LHT bolt on the top , it has an ali ringnut with very small spigot holes . It looks like the ring on the bottom but a lot smaller. In view of the recessed position I won't even be able to get a pin-wrench on there, I'll have to make a more complex tool. I can see this ending with a hammer and chisel and me looking around for large, fine threaded LH tap !!

I'm going to try drying this out in the oven. I pre-heated the oven to 95 deg C ( IR thermometer ) , cut the gas and put the body in. I'll let it sweat it out for a while.

IIRC the operating temp is spec'd for about 80 degrees. I guess the Achille's heel is the plastic seals and guard-rings. The winding's varnish should resist a lot higher than that.

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Drilling the hole was a bad idea, this will mess up the balance it is normal that you have to make wrenches to suit what is needed, if you damage any parts then you should buy a new spindle as the damaged parts have to be replaced because of the balance required at high speed can not have any damage to the rotating parts

Heating up could help to get the moisture out as long as it can find a way out

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Originally Posted by mactec54

Drilling the hole was a bad idea, this will mess up the balance it is normal that you have to make wrenches to suit what is needed, if you damage any parts then you should buy a new spindle as the damaged parts have to be replaced because of the balance required at high speed can not have any damage to the rotating parts

Heating up could help to get the moisture out as long as it can find a way out

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Don't worry, I did not drill the moving parts. Just the static ring which is screwed over the bearing block.

It does now run with out tripping out but I have yet to seal it up and refill the coolant circuit.

Quote:

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Originally Posted by reg.miller

Don't worry, I did not drill the moving parts. Just the static ring which is screwed over the bearing block.

It does now run with out tripping out but I have yet to seal it up and refill the coolant circuit.

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Need to see some photos of your spindle it sounds like it has a different front mounting and the back retaining bolt seems to be different as well

Hi, it's very similar to the one shown in this thread:
https://www.cnczone.com/forums/spind...ml#post1093542

In the top centre photo, it's the smaller of the two black rings which I drilled to gain access to the Allen screws in the larger one.
That one seems to have a similar top bolt to the one you describe, mine has a ring-nut with spigot holes. The shaft is threaded on the outside. I can't photograph it now since it's sealed with silicone sealant and the water cct is full.

A friend lent me another one which was slightly different again but basically the same design. They probably copied one basic design and then just make trivial changes so as to pretend they have their own designs and have not violated copyright.



So far so good ...

I preferred not to open it this time, as long as it does not show more problems. But at least I have a pretty good idea what I'm looking at the day I do need to service it That's more than I could say last week. Many thanks for sharing your detailed knowledge of these things, it was an immense help. ;)

Quote:

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Originally Posted by reg.miller

Hi, it's very similar to the one shown in this thread:
https://www.cnczone.com/forums/spind...ml#post1093542

In the top centre photo, it's the smaller of the two black rings which I drilled to gain access to the Allen screws in the larger one.
That one seems to have a similar top bolt to the one you describe, mine has a ring-nut with spigot holes. The shaft is threaded on the outside. I can't photograph it now since it's sealed with silicone sealant and the water cct is full.

A friend lent me another one which was slightly different again but basically the same design. They probably copied one basic design and then just make trivial changes so as to pretend they have their own designs and have not violated copyright.



So far so good ...

I preferred not to open it this time, as long as it does not show more problems. But at least I have a pretty good idea what I'm looking at the day I do need to service it That's more than I could say last week. Many thanks for sharing your detailed knowledge of these things, it was an immense help. ;)

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There are many different designs with these spindles on how they are put together

You don't want to remove the Bearing Housing unless it needs something done to it, the front Bearing cover is all you have to remove, the Bearings and rotor will slide right out the front, in the link you posted that should of not been done like that