[kafie1980]

hello everyone,

my bad but my I burned my spindle during my early tests setting up the VFD and i most probably damaged the insulation on the motor windings. My VFD kept shutting down the spindle after a quick run, displaying EOCA error. Yeah, I know I was'nt supposed to run the spindle below 100hz but I was distracted and it happened. the magic smoke appeared and the spindle was too hot to even touch. well I dont feel too bad about it now after what I learned by dismantling it.

I do see several people posting about water cooled spindles but there are rarely any posts showing the internals of a cheap typical round body air cooled spindle from AliExpress.

I bought the spindle from AliExpress and it costed me about US$120 shipped to my door step. It was laying around in a box for over an year before I built the courage to focus on putting together my semi DIY CNC router.

Below is a quick snapshot of the spindle details posted by the seller (i am keeping the sellers details anonymous, they are all the same anyways):



You can read from the item posting above that the seller claims the spindle contains 2 sets of 7002C German Angular Contact bearings. well, you would wish for that price, cause even a set of Chinese made Angular Contact bearings will cost you about US$25 shipped which would mean US$50 ish for 2 sets. Wow, what do the rest of the parts used to make the spindle cost. just imagine, well lets comes back to the bearings a bit later on.

I decided to dismantle my spindle from a perspective that I wanted to have a look inside and see if I can have someone rewind the motor windings for me. I know it will probably cost me more than the spindle to rewind the spindle but I just thought I try and resurrect the spindle.

So with just a few basic hand tools, I didnt even have a vice at hand (all my stuff is still stored in boxes and I havent setup shop yet), screw drivers, hex keys, round nose pliers, some heat, and some elbow grease, I managed to pull it apart.



I didnt really follow the same sequence, but a few things to point out:

- if you start with item No. 1 followed by No. 2, you will encounter the fan that is not shown in this picture because I destroyed it in the process and is probably on my neighbors roof top right now cause I lost my temper (im cool about it now). The fan is a basic direct shaft mounted assembly made of some plastic.

- Item No.10 will be encountered in between item No. 3 and is a LEFT HANDED bolt made of some soft aluminium, with the fan glued to the head. Please remember, LEFT HANDED because this is where I ended up destroying the fan. There is also some thread-lock on the threads but you can carefully heat it up to break the bond.

- Item No. 8 is a press-fit and you will need to carefully drive it out once you finish removing all other items such as the spindle shaft, bearing etc. I just used the wooden handle of a hammer to drive it out from the opposite side.

- Item No. 15 is a lock nut of some some aluminium, the threads have some thread-lock and you will need to heat up the part carefully before you can unscrew it.

Now some observations that I made were:

- The machining work is very good quality, the bearings etc easily slip fit onto the shaft.

- The spindle (Item No. 11) had no grease whatsoever and the spindle shaft had plenty of rust. I initially assumed the spindle overheating may have burned the grease but then again it just burned a few weeks ago and i do not think i would expect such a high rate of oxidation. Item No. 8 was bad rusted towards the inside as well.




- The spindle shaft shows evidences that it has been balanced as we can see balancing drill holes on various sections of the body.


- The spindle enclosure itself is like a aluminium fin extrusion fitting inside a steel round body probably using some heat shrink fit method. Here is top and bottom view of he spindle body also showing the damaged windings:




I know its starting to get boring but I have one more important picture to show, remember I mentioned earlier that sellers on AliExpress claim German Angular Contact Bearings (my seller mentioned 7002C Angular Contact Bearings), these are what my spindle came with:



Yes yes, there are no German angular contact bearings, these are just cheap Chinese made NSK 6002V Deep Groove Ball Bearings. All four bearings are NSK 6002V, no angular contact bearings, no way, hell no.

What a rip off? A Day Light Robbery! I mean even if they were Chinese Angular Contact Bearings, I would have accepted it to some extent.

And then I realized, the NSK 6002V and the NSK 7002C have the same exact dimensions: ID 15mm, OD 32mm and Thickness 9mm. I compared dimensional values off the NSK brochure.

Well with cheap 6002V's this spindle wont last too long and forget the runout precision claims over time. Infact, to add to it, 2 out of 4 of the bearings in my spindle are already sluggish and do not spin freely when compared to each other just running the spindle on and off during tests is just a few days.

By the way, the logo on my spindle body is shown below:



I posted the above information to warn others about the quality issues with these spindles.....

I burned the spindle and its my fault, it has nothing to do with the bearings for now, but the bearings would have caused me more pain in the future, I am not able to claim warranty or return of the item because my purchase was made more than an year ago.

I may not be able to repair this spindle because I am not sure if I can have it rewinded, but i would be very careful buying a spindle from AliExpress again. I have purchased well over a few hundred items off AliExpress but this is the first time I have actually regretted it so much.



cheers,
kafie1980

[Chris D]

Kafie1980,

Thank you very much for posting this information. As you suspected from the beginning, there is no way there were German bearings in that spindle based on the selling price - "If it sounds too good to be true, then it must be too good to be true".....

Aside from that, I am surprised that the spindle looked that bad, I mean really? I know the price we pay for Chinese made products dictates what we get, but that is some serious rust on that! At that point, it barely fits into the category of typical Chinese made products of "Well, at least is looks like (insert product name here)!"

I have the 2.2kw air cooled version of this spindle - probably from a different ebay seller, I'm hoping it will last a little while at least.

Chris D

[kafie1980]

Chris,

I felt the same about the rust i saw inside the spindle and the condition of the other parts. so far i have just cleaned all the parts using kerosene and scotch-bright to get rid of much of the visible rust, lightly lubed, sealed and put in an airtight bag all the parts.

i dont know if any of the internals can be of use in the future. not even the bearings are worth keeping as 2 out of 4 are dry and sluggish to even rotate freely (i think they are fake NSK's as the NSK bearings on my motorcycle have lasted several years without failure) and the fan fins broke while dissembling the spindle.

im even worried that if i bought another spindle, it may end up in such bad shape with inferior bearings, rust, no lubrication etc.

i might just buy the cheapest spindle i can find off aliexpress/ebay and replace the bearings to quality angular contacts myself.

but im still studying my options.

i visited an old timers' commercial shop whose family business is repairing electric motors and spindles for a living. he had all the services available for rewinding, balancing etc but he is not able to work on a motor this compact.

i dont feel i want to spend another few hundred dollars on an un-trust-worthy spindle.

i even contacted the seller regarding the bearings being only 6002V's and the broken fan, but they ignored the bearing issue and offered to send my a replacement fan for free but i still pay shipping.

the sellers definitely know they are selling us junk so to speak.

all the people posting good reviews either have been lucky to receive good spindles (fingers crossed) or they will eventually find out if any failures occur and they just might justify the cost as a cheap replacement anyways after the spindle has given them X number of hours of duty.

well, if you have one then feel lucky its still running, but if you are going to buy one then better think twice about it.

kafie 1980

[RCaffin]

You got it cheap?
The vendor probably KNEW about the rust and the crook bearings when he advertised it.

Do you have continuity in the windings? Is there a short to the frame? With zero value left, you can afford to play a bit.

Cheers
Roger

[kafie1980]

Roger,

When I said "cheap" I meant for getting a high speed spindle motor for about US$120 shipped to my door. Maybe a dremel might cost cheaper or even a wood router, depending where you live. A similar specification spindle from any name brand will cost us 3 to 4 times more.

I cant blame the vendors or the resellers completely, probably they knew what they were selling, probably they knew they were compromising on quality. The question is how many of us actually dig deep into any of this and decide to post that they have been ripped off?

The windings were even inspected by a professional spindle repair specialist yesterday visually and with a multi-meter and he confirm the windings are badly damaged. But they cant rewind it for me because they dont work with motors this small and compact. so i am having fun playing with it and who knows maybe i just toss it away in the trash or end up getting it to run again even if its for a short life, sometime, somehow.


Cheers,

Kafie1980

[ger21]

The question is how many of us actually dig deep into any of this and decide to post that they have been ripped off?

Were you really ripped off? You damaged the motor, and have no idea how long it would have lasted. I paid $200 each for two 2.2kw air cooled motors. If they last only 1 year, I won't feel ripped off, because I bought the cheapest motors I could find. Any chinese spindle under $400, I would consider that you're taking a chance on it. Consider them disposable.

[kafie1980]

Gerry,

I did confess when I first posted that I burned my spindle during initial tests. I was using a vfd for the first time in my life. ha ha ha

My point of the post was showing the internals, if anyone was interested. All i wanted everyone to know is that there are no Angular Contact Bearings in some of the cheap spindles we are buying.

Yes, I agree I knew I was buying a cheap spindle.

Most of my stuff comes from sellers on ebay/aliexpress, and I do go for the cheap stuff to keep my hobby costs low. And so far the cheap stuff I have received is what it says in the item description.

What I mean by a rip-off was the seller advertising that the spindle had 7002C Angular Contact Bearings where as actually they came with 6002V Deep Groove Ball Bearings.

Some maybe have been lucky to have dealt with a honest vendor and received a good spindle.

I agree with it being disposable, but it has to be what it reads on the label. And many of us just read the label and believe it.

Cheers,
kafie1980

[RCaffin]

And many of us just read the label and believe it.
Which may explain the strange results of a recent election.

I have given up buying cheap. It often works out more expensive. I end up having to buy two things rather than one.
Exception: when I am planning on using the first (cheap) one as a learning exercise rather than as a long term purchase.

Cheers
Roger

[dharmic]

I'm still a bit of a fan of the "buy cheap once" approach when it comes to tools. Get a cheap one, or a cheap set. Most of the time it's fine, or you use it so rarely it can cope. When you break that one spanner / socket / collet / spindle / whatever or your cheap 0.01 gauge turns out to be more like a 0.92 gauge, go and spend the money on a better quality (you hope) replacement. Surprises me how rarely I actually need to do this.

[mactec54]

there are no German angular contact bearings, these are just cheap Chinese made NSK 6002V Deep Groove

The seller would have no clue as to how the spindle is constructed, they just buy and sell

They are not worth repairing at this stage, the Grease would of left the Bearing with that heat, it just boils in the bearing and the pressure forces it out of the bearing past the seals

The construction of your spindle is no different than a water cooled spindle, except for the Bearing type and arrangement

The Bearings made in NSK China, has the same spec / quality Bearings as NSK Japan, they are not cheap, NSK is one of the top Bearing manufacturer's, what you have is not a standard grade, they are a precision grade bearing, and quite suitable for your spindle use, if it was built correctly

The word German Bearings, is a name used by may Chinese manufactures, and is true, the Bearings could well of been made in a German Bearing Factory in China, Some years ago almost all the German Bearing manufactures moved to China, so there are very few Bearings made in Germany any more, all that is left in Germany is for special Bearings

The rust was from the burn up of the spindle, can be very corrosive and toxic depending on the coating

Now just think if you had set the VFD Parameters correct, your spindle would be running and you would of been a happy camper, and saying how good this spindle was

A good write up though, even if it is not all correct

[KH0UJ]

If the OP wants more challenge on it, I guess he can rewind it using a hermetic type magnetic wires, he now have the option to make it torquey with 4 poles divided by the RPM (12000) or stay on the 2 pole design which is the 24K RPM, on my side I can rewind that for an hour and it will be more durable than it`s previous state

[RCaffin]

The word German Bearings, is a name used by may Chinese manufactures, and is true, the Bearings could well of been made in a German Bearing Factory in China, Some years ago almost all the German Bearing manufactures moved to China, so there are very few Bearings made in Germany any more, all that is left in Germany is for special Bearings

Really?
I learn something new every day.

Mind you, given how the mfr of bearings is so highly automated these days, one would have to wonder why they would have moved the factory to China. Bet they regret doing so now!

I can rewind that for an hour and it will be more durable than it`s previous state

I can believe that, but DETAILS PLEASE! How?

Cheers
Roger

[mactec54]

Really?
I learn something new every day.

Mind you, given how the mfr of bearings is so highly automated these days, one would have to wonder why they would have moved the factory to China. Bet they regret doing so now

Cheers
Roger

I have posted this before about the German Bearings Name used in China, this gives you an idea how wide spread that major companies operate in China this is just one country, they even have a Directory's setup for each country

German Company Directory | Greater China
With more than 5,000 company profiles and 6,000 contacts, the German Company Directory Greater China is the most comprehensive and up-to-date directory of German companies in Greater China.

[RCaffin]

Hi Mactec

URL for that Directory?

Cheers
Roger

[mactec54]

Hi Mactec

URL for that Directory?

Cheers
Roger

Just do a search it's easy to find, they have a major BMW car plant there also

BMW hit 1 million cars built there last year there manufacturing plants are amazing

Part of the Shenyang site is a stand-alone engine plant (Powertrain). It provides the two vehicle plants Dadong and Tiexi with drive systems for the BMW cars produced at these factories.
A larger second engine plant that also comprises a foundry (New Engine Plant) is currently under construction; it is scheduled to start operations in 2016.

[Eldon_Joh]

If the OP wants more challenge on it, I guess he can rewind it using a hermetic type magnetic wires, he now have the option to make it torquey with 4 poles divided by the RPM (12000) or stay on the 2 pole design which is the 24K RPM, on my side I can rewind that for an hour and it will be more durable than it`s previous state

its a 65mm outside diameter spindle.

you really think you can rewind that?


as for the bearings.. no surprise to me that they lied about the bearings, as implied by the price; but.. if they are properly preloaded and thermal expansion taken care of, it would not surprise me if 6002's would hold up, if the rotor was also dynamically balanced, as its "only" 24,000 rpm, and probably 750 watts real (if that many), not 1.5kw Chinese..

as for how you burned out the wiring.. if the instructions said don't run it below 100hz then they had the boost volts configured in the vfd to overcome saturation and start up torque just to spin the bearings, and the heat caused by that additional voltage was too great for the airflow the fan would offer below 100hz (which would be 6000 rpm).. such "efficiency" would account for the 1.5KW rating. that's the input watts.. output watts is probably half of that.

[RCaffin]

you really think you can rewind that?
Well, the Chinese managed to make it in the first place.
Academic exercise for the lols.

Cheers
Roger

[KH0UJ]

Technically it`s just a basic three phase motor, the core on that can be taken out by for easy rewind, rewinding a three phase high frequency motor is easier than rewinding a single phase 60HZ motor, honestly if that motor is mine I will rewind that for better performance, better insulation by using a poly urethane paint than the basic electrical varnish, for the price point it`s cheaper for you guys but for me it cost a lot already, it`s cheaper for me to rewind it if it`s burned, now I have the option to improve it`s stability and reliability, to cut the story short im poor, but being poor is not really a disadvantage for me, my mind looks for solutions for cheap products to be a better product after the modification

[RCaffin]

I'm with KHOUJ, but for a slightly different reason. I just don't like being beaten!
Plus there is a chance to learn something new here.

Cheers
Roger

[kafie1980]

So far this thread has been bashing me with burning the motor and the assumption that if I had my VFD setup right then I would never have burned the motor and I would be happily praising about its quality and performance. but i am really enjoying it because I am getting to learn a lot. and the write up was what i found after I opened up the motor, the bearings, the dried up grease or rust, its all just my personal assumptions on what I could see.

Some of my assumptions maybe wrong, I am a Geologist after all and do all my work based on assumptions and observations.

So my plan to rewind this motor is still ongoing and then put in some quality bearings that I can source locally.

I can simply buy a motor off AliExpress and be done with it, but since its for hobby work I can spend some time waiting to see my options. Maybe I can end up with a better spindle than before even if everyone doubts it.

But I do appreciate everyone giving me advice (whether its good or bad, i will have to wait and see).

For now, i have left the spindle frame with a rewinding technician who says he will take a look at it and let me know if he can rewind it or not. Again yes, diameter of the spindle is the concern for the people I have shown the spindle as there is nothing special about the winding that they dont understand just that they dont like getting their hands into such confined spaces.

Hey Khouj, if you are looking for a project then I can send you my spindle for rewinding, (I assume you are in the Phillipines and I am in Malaysia). I dont mind if we can squeeze more torque out of it, like you say rewinding it to a four pole may be an option. I can pay for the shipping and rewinding costs. Let me check by Monday and you let me know how you feel. If we fail, dont worry, no regrets.

If not, you have still given me a great idea, I didnt think about taking out the core and sending it for a rewind job. I assume its just press fit it. Let me wait to get my spindle frame back if the technician cant do it.