Seal design

[JeanMicheling]

Hello folks,

I'm designing a new spindle and I'd like to have a great seal design. I got some information with skf but i'd like to have something more relevant. Does someone have an idea where I can find more information?

Thanks for any help

 

[EnglishMuffin]

Sorry JeanMicheling and others - I am misleading everyone. It wasn't the University of Aachen - it was the University of Stuttgart.

Title : Konstruktionsrichtlinien fur beruhrungsfreie Spinddelabdichtungen im Werkzeugmaschinenbau - Teil 2

or "Construction Guidelines for Non-contacting Seals of Spindles in the Machine Tool Industry". Part 2

It was created by order of the association of German Machine Tool Manufacturers.

University of Stuttgart - Department of Sealing Technology

Authors : Leader : Prof Dr. Eng. H.K Mueller
Project Leader : Dr. Eng. W. Haas
Expert : Dipl. Eng E. Fritz

 

[Tmoose]

In machine tool spindles it is easier to keep oil residuals in than to keep high pressure coolant out. The spiral is set up to pump coolant back out. The oil is managed internally with conventional flingers and drain grooves. Essentially 2 sets of "seals," at least at the working end of the spindle.

Either way, there is one direction of operating rotation.

 

[JeanMicheling]

EnglishMuffin, It seems that this document is not available on the net. Is it translate in english or you did it yourself?

The pumping effect of a seal is pretty interesting. I have some machines with vertical spindles with radial seals. The seal diameter grows from the inside of the spindle to the outside. So on a vertical spindle, for the top side, the pumping effect fights the gravity which is great. But for the bottom, the pumping effect flows with the gravity and I'm afraid that it could pump out both the seal and the bearing grease.

 

[Tmoose]

Keeping the grease in is relatively easy.

Keeping the bad guys out is tough.

There are a few machine tool exmples here.

http://www.fag.com/mediaDB/rel PubL...-/-/schaeffler_internet/WL_00200_5_T2-8_de_en

 

[JeanMicheling]

Tmoose, there are a lot of interesting design in this document. I discussed with a guy from NSK and he didn't agree on using a re-filling grease system with precision bearings. I looked at some grease valve and it doesn't seem to be so hard. Does it work well? Have you ever tried that?

 

[Tmoose]

Greased for life can be a great spindle solution.

Getting the right grease, in the right (small) quantity, uncontaminated and evenly distributed into precision bearings thru a fitting or (?)in a "high speed" spindle would be a miracle.

One of hybrid ceramic bearings legitimate claims to fame is markedly improved "grease life." HC bearings, lubed at the factory with one of the super synthetic spindle greases, with non-contact "seals" (shields, to my way of thinking) are a pretty impressive product. It takes aggressive sealing, excellent manufacturing and craftsmanship to let them perform to their fullest.

 

[EnglishMuffin]

We have just had a visit from the CEO of Weiss (a leading German spindle manufacturer) - and he said they have just developed a state of the art grease lubing system which replenishes the grease automatically at intervals, and you don't have to stop the spindle. I think it is going to be in either the next EMO show or IMTS in September. It is based on automatic truck chassis lube technology, with modifications. You get unlimited grease life.

 

[JeanMicheling]

I tried the non-contact seal with 7020 precision bearings. They are still in the field and everything looks ok but they are really expensive. I don't think they are worth their prices since I can buy an inpro seal for instance with the price difference. By the way, the inpro seals are really expensive too but look highly efficient. The question is are the worth their price. I was using radial seals which were not working too much and I tried axial seals (pretty standard design shown in skf book) and they work quite better. However, on my new spindle, if I go with grease, I'll give a try to the inpro seals but if I use a oil-mist, a simple axial seal will do the job! So, to resume all the interesting texts we have here, air purge is the best seal you might have and if not, inpro seals would be a good choice?

 

[Tmoose]

http://www.eng-tips.com/viewthread.cfm?qid=80034

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Which Inpro are you speaking of?
The front door link to machine tools took me to the VBX series.

More digging revealed Air Mizer, which is here.

http://www.globalspec.com/FeaturedP...ng_Isolators_for_Machine_Tool_Spindles/8392/1

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The Air mizer appears to have airpurge (with a drain) on the work side, and the flying o-ring on the bearing side.