DM4400 Spindle bearing repair

[oscilloman]

Hello

Couple of weeks ago i purchased a DM4400 running the old skip controller. I gave it power and all the axis would home perfectly. I was able to release the spindle brake, but the spindle would not turn because it was not getting any power from the 3030 driver. Looking at the spindle servo driver it lit up with a red diode for GF, meaning ground fault i guess. Not really a surprise, because the entire control cabinet had a layer of oil and some type of dark sot. I disassembled the servo dynamics 3030 drive and found a defective diode on the 3phase bridge rectifier. Tried replacing the diode and powering it back up, but still got the GF error.
After this I released the SEM spindle motor from the spindle it self and tried turning the spindle by hand. By surprise it would not turn more then a 1/8 turn in both directions . Turning it CW and CCW a couple of times it would finally release and would turn ''freely''. It makes a really bad noise when it is turning so i suspect one or more of the bearings are shot and would need replacing.
I have started to disassemble the spindle but I got stuck after removing the belt pulley, I've added some pictures of a nut that I am guessing is holding the spindle up. I think it is threaded on, but it will not move even after heating it with a propane torch.

I would really appreciate some input on how to disassemble the spindle!




The outer flange with bolt holes is not connected to the shaft, its only the nut with a tapered hole drilled in it for a setscrew that is connected to the shaft. I've made a custom tool to hold this nut while turning the shaft. But it will not move. maybe it have left-hand threads? Or is it slip fit, i really don't know.

-Mathias

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[drhanger]

Hi Mathias-

Here is some info I got directly from DynaMechtronics (Roberto) about replacing the bearings:

Hello Mr. Dan to replace the bearings , you may need an oil injector to remove the ring plate #13 is the location where you will be injecting the oil to pressurize it in order to pop it (loosen it) then you can remove the rest..
See attached as a reference only and to give you an idea of what is needed..

Now for the Bearings on the Spindle , there are only two types inside the Spindle cartridge.
Fig# Qty. Specs.
#10 x 1 NN3007K
# 4 x 3 7008AC/TBTB


The Dyna Part # T0507-03007-FAS
We do not have it in stock ,but you can check the following links and see which one will be better in terms of cost for your Company.

.SKF NN-3007-KSP BEARING | eBay

SKF NN 3007 K-SP,NN 3007 K-SP bearings,Cylindrical Roller Bearings NN 3007 K-SP,Size -35(mm)*62(mm)*20(mm),

https://www.123bearing.com/bearing-NN3007K-KOYO.php

https://www.alibaba.com/trade/search...chText=nn3007k


Fortunately we still have some of the 7008 Cylindrical Roller Bearing in stock Total of 6 pieces.

The Dyna Part #T0501-07008-BAW
Cost Each : $150.00 usd
Stock : 6 Pieces Available

Let us know if you will be interested on purchasing this one from us.
If not then you could probably search on the web to find some more
Which may be more economical for your company.

Best Regards, Roberto

Dyna Mechtronics.,Inc.
1435 Koll Circle Bus. Pk. Suite # 107
San Jose, CA 95112
Tel: (408) 452-1010
Fax: (408) 452-1099
E-mail: services@dynamechtronics.com

I am attaching the files he sent me below. I would recommend removing the spindle cartridge before you do anything else. See the diagram--remove the 6 M6 bolts at the spindle nose (#11) first. Then you can use something to pound it out from the top--I used an aluminum tube with about 2-1/2" ID so I wasn't pounding on the upper bearing in case it was still good.

If you get anywhere with this keep us informed--I have bad bearings in one of mine as well (I bought two at the same time and swapped the good spindle from one I have in storage into the one I am currently using) so would be interested in your progress. I don't think it's something I would really want to do myself as I understand it requires a lot of experience and know-how to do spindle bearings right, but if you've got what it takes it would be nice to see it done.

If you do remove the cartridge let me know, I'll tell you how to get it back in pretty easily. Actually there's not much to it, I put the cartridge in the freezer for a few hours while placing a space heater on the spindle casting overnight. It slipped right in easily; without doing it this way it's a real PITA otherwise.

Dan

[oscilloman]

Wow, thanks Dan! This will help me allot!

I do not have the experience working with spindle assembly's, but have replaced a few bearings at work. I will look into getting this professionally done, however I am guessing there is no such company anywhere close to me.

Have you succeeded in removing nr:13 on the spindle assembly drawing? If you have, how did you do this?

-Mathias

[drhanger]

I have not attempted to disassemble the bearing stack, so can't tell you anything other than what I posted from DM. You would need some kind of injection nozzle and probably a small manual hydraulic pump. If I felt confident about doing the bearings myself I would look into it further, but haven't, and don't really want to spend the money for it right now as I have one good working machine now and at the moment it's just mainly for hobby and astronomy equipment development. Since it's not really a high speed spindle it's probably not as critical, to me it's mainly a matter of how long the bearings last if I don't do as good as the experts. If I was planning on heavy production with it, I would definitely let the experts do it, and production work would make it easier to justify the cost.

[oscilloman]

As I understand you have removed the spindle cartridge? And then you had to remove the stepped collar? (nr:13 on the spindle assembly drawing)
This will not be a production machine, only simple prototype work will be done on it.
Again, thanks Dan this really helped me!

-Mathias

[drhanger]

Hey Mathias-

Your post inspired me to take another look at my bad spindle just to see how far I could get with it. By the way, I was mistaken about the cartridge screws for removing from the machine, I thought those were the ones labeled #11, but actually those screws aren't even showing in the drawing, and they're bigger than the #11's. Anyway, I removed all the #11 screws at the top and bottom (item 3 and 12, 6 each) and set it in a vise on the large flange, standing straight up in the vise. I screwed the threaded pulley collar on the end of the shaft and hammered on it with an aluminum drift. It didn't take that much persuasion to push the inner shaft out of the cartridge, so I didn't need a hydraulic pump to pop the collar (#13) off. The picture is of the inner shaft with the bearings showing. The top bearing apparently is two piece, the outer race stayed with the outer body of the cartridge. After that my luck ran out. From the drawing I could see that all that remained to get all the bearings off the shaft was to keep pressing on the top which would in theory push the spacer ring (#7) upwards, pushing the top bearing off along with the rest. But that wasn't going to happen--that spacer ring was tighter than tight, and even heating it didn't break its grip. So that ring for sure needs the hydraulic pump to move it, and of course with new bearings you sure wouldn't want to be hammering it all back together, so I think your only option is the hydraulic pump and injector, or back to the pro's again.

[oscilloman]

Dan, I cant thank you enough for taking the time to disassemble the spindle on one of your machines. You saved me allot of head scratching!
A couple of days after your last post I did exactly what you did and I got the inner shaft out. It seems that the roller bearing is OK. But I will probably replace that also while I am at it. All three of the 7008AC/TBTB are shot and will need replacing. No wonder, because the upper bearing have a broken seal, and it sure looks like there is rusty liquid on the inside.
Lucky enough the roller and ball bearings are easily available here in Norway. But they are pricey. The cheapest supplier i could find would sell me one NN3007K and
three 7008AC/TBTB for no less then 1274USD (11000NOK).

What do you think about using a hydraulic press to force the spacer (nr-7) and the ball bearings off? I would turn a spacer that fits over the drawbar and press it from there?

[drhanger]

Glad I could be some help to you, Mathias. Have you checked with Roberto at DynaMechtronics about the bearings? The email I posted from him upthread said he had 6 of the 7008's at that time, selling for only $150 US, if he still has any. I don't know what international shipping on such small items would be, but I can't see it being near the cost of your local supplier. Don't know about pressing the bearings off, I'll have to study it a bit. Not sure where and how you would press on them. That spacer ring didn't budge at all as far as I can tell, even with lots of heat and heavy pounding. I guess pressing can't make the bearings any worse, but not sure how you'd get the new ones on without excessive force and possible damage.

Dan

[oscilloman]

I have made some progress..



I made a box out of wood to hold the mounting bolt flange in place, and used a bottlejack to push from the other end.


Drilled and tapped a hydraulic coupling to M8. Used a threaded M8 rod and turned one side (7-8mm) of the rod to M4. That is the oil injector hole size. And then drilled a 2mm hole trough the entire rod.


I used a cheap 4ton manual hydraulic pump as the oil injector pump.


Here is the sleeve where I injected hydraulic oil. The manual recommends a oil with viscosity of 350ES (46 E Degree) I used what came with the pump (ISO32 I think)


I used a piece of pipe to fit over the draw bar.



I pumped the bottlejack a couple of times to hold the entire thing in place, and then pumped quite hard on the hydraulic injector pump. Applied a little bit of heat on the sleeve (30-40Celsius), and then pumped some more on the bottlejack. It was pretty easy to be honest, not much force needed when you load up the sleeve with oil. When the sleeve released, it sprayed hydraulic oil all over the place, so make sure to wear eye protection, thick gloves and clothes just in case anything on the hydraulic side decides to go boom.
Here is a mockup without the injector pump connected.


I have ordered new bearings, so I have to figure out a safe way to get them back on...

[drhanger]

So far so good, I guess. Did you order new bearings from the source I mentioned, or the local ones?

[oscilloman]

Got them from a dealer in Norway. Dyna Mechtronics wanted 210$ for them now, and I have to add 25% in import taxes to Norway. I would probably save some money by purchasing them from DM, but I feel safer when purchasing from a local dealer. However, thanks for letting me know of that source Dan!
New bearings are due to arrive in 10 days.

To get them back on, I am thinking of using a aluminum tube that fits over the shaft and only presses on the inner ring of the bearing. Use it in the same box i made earlier and press them on one by one. I will put the shaft in a freezer and heat up the bearings before i do any of this. Any thoughts, positive or negative is greatly appreciated

[Marty_Escarcega]

Got them from a dealer in Norway. Dyna Mechtronics wanted 210$ for them now, and I have to add 25% in import taxes to Norway. I would probably save some money by purchasing them from DM, but I feel safer when purchasing from a local dealer. However, thanks for letting me know of that source Dan!
New bearings are due to arrive in 10 days.

To get them back on, I am thinking of using a aluminum tube that fits over the shaft and only presses on the inner ring of the bearing. Use it in the same box i made earlier and press them on one by one. I will put the shaft in a freezer and heat up the bearings before i do any of this. Any thoughts, positive or negative is greatly appreciated

So hoe does this story end? :-)