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