Author Topic: Any advice on pressurizing (grinding) spindle?  (Read 1229 times)

Offline PekkaNF

  • Hero Member
  • *****
  • Posts: 1813
  • Country: fi
Any advice on pressurizing (grinding) spindle?
« on: June 15, 2017, 11:29:56 AM »
This got me thinking...
http://madmodder.net/index.php/topic,12170.msg144823.html#msg144823

Has anybody made/mod. pressurized spindle?

Many spindles have ZZ non contact seals for low friction, not that great against abrasives. RS would seal whole lot better, but sucks on high rpm.

https://image.slidesharecdn.com/1-141227035803-conversion-gate02/95/11-bearing-types-and-appl-guidelines-17-638.jpg?cb=1419674474

Traditional way would be to use labyrinth or such and use over pressure to block contamination route into bearings. To construct that on existing spindle demands bit more head skratching.

So, what are other choices? Haven't got into microns yet, but is it a good idea to pressurize plenum between two ZZ seal ball bearings - idea being that some air is expelled from bearing seal annulus and hopefully that would expel dirt coming into that way. It would need a flinger at the front of it stop direct spray.

I see here few problems, but is that serious?
1: Small annulus on ZZ seal - translates to low flow and small cleaning -> put a simrit ring next to it?
2: Pressure pops out seals -> lower pressure.
3: Dirty air contaminates bearings -> best to avoid getting that trough bearing, but that was the whole idea here->filter the crap out of pressurized air.

Completely stupid idea or has some merit?

Thank you.

Pekka

Offline philf

  • Hero Member
  • *****
  • Posts: 794
  • Country: gb
Re: Any advice on pressurizing (grinding) spindle?
« Reply #1 on: June 15, 2017, 05:29:28 PM »
Pekka,

What size of bearing are you thinking about?

A 10mm X 26mm OD rubber sealed bearing is good for 30,000 rpm.

I don't like the idea of pressurising between the bearings - there's a risk of forcing out the grease which you wouldn't want and, as you say, there's a risk of blowing dirt or moisture in.

Standard deep groove bearings are cheap enough to consider them as consumable.

Phil.



Phil Fern
Location: Marple, Cheshire

Offline PekkaNF

  • Hero Member
  • *****
  • Posts: 1813
  • Country: fi
Re: Any advice on pressurizing (grinding) spindle?
« Reply #2 on: June 16, 2017, 03:37:20 AM »
There are two 6002 Z bearings on front. 15x32x9 mm and one smaller bearing on rear.
http://www.skf.com/uk/products/bearings-units-housings/ball-bearings/deep-groove-ball-bearings/deep-groove-ball-bearings/index.html?designation=6002-Z

Spindle is from 900 to 6000 rpm, speed vice fine with RS, but it will rob some power, the spindle is only 250 w.

Will dump the trough purge/lube idea and change the bearings....everything seems to be glued, staring from set screw, to bell housing.

Pekka

Offline philf

  • Hero Member
  • *****
  • Posts: 794
  • Country: gb
Re: Any advice on pressurizing (grinding) spindle?
« Reply #3 on: June 16, 2017, 03:54:38 AM »
Pekka,

I'm sure with a 250W motor you'll be fine.

My grinding spindle for the lathe has 15 X 24 X 5 2RS bearings and only has an 1/8hp (90W) motor and it still has enough power to grind.

Phil.
Phil Fern
Location: Marple, Cheshire

Offline PekkaNF

  • Hero Member
  • *****
  • Posts: 1813
  • Country: fi
Re: Any advice on pressurizing (grinding) spindle?
« Reply #4 on: June 16, 2017, 01:31:00 PM »
Thank you Phil,

What rpm is your grings spindle? Any pictures?

Some rubber selas are pretty stifs some have very little friction, some will ease pretty fast.

This is pretty slow speed drill/mill spindle and here it was used to true wobbly diamond wheel.

Got three opening sticks from loval shop to open diamond wheels, two are ment to be used wet but one is intended to be used white, it is weird, feels like heat shied foam!

There is one stubborn set screw, 2,5 mm hex key is loose, 7/64" and 3,0 mm does to fit!


Pekka

Offline philf

  • Hero Member
  • *****
  • Posts: 794
  • Country: gb
Re: Any advice on pressurizing (grinding) spindle?
« Reply #5 on: June 16, 2017, 04:00:32 PM »
Hi Pekka,

I think the max speed is about 8,000 rpm using a 3,000 rpm motor. I'll put a tacho on it to see. I have a 2-step pulley and think one ratio gives me 1:1. [Edit: I was close - 3,500 rpm and 9,000 rpm.]





The attachment in use cutting a ballscrew:



The spindle takes 8mm watchmaking collets and arbors. I have a Quorn T&C grinder which uses the same arbors so can use the wheels made for that.

The attachment fits in place of the quick change toolpost. The bore for the bearings was machined in-situ so the spindle is at the lathe centre height.

I reground my D1-3 spindle nose with it and have reground the jaws on several chucks.

The motor came off a small pump and I thought it may be too small but if I take things easy it's OK.

Phil.
« Last Edit: July 13, 2017, 12:52:40 PM by philf »
Phil Fern
Location: Marple, Cheshire

Offline PekkaNF

  • Hero Member
  • *****
  • Posts: 1813
  • Country: fi
Re: Any advice on pressurizing (grinding) spindle?
« Reply #6 on: June 16, 2017, 05:16:44 PM »
That is a very nice ginding spindle. Quorn-type bearing arragement?

Thank you for showing that, it is very inspirational.

Pekka

Offline philf

  • Hero Member
  • *****
  • Posts: 794
  • Country: gb
Re: Any advice on pressurizing (grinding) spindle?
« Reply #7 on: June 16, 2017, 05:43:57 PM »

Quorn-type bearing arragement?


No - just two identical 15 x 24 x 5 bearings with a spacer loctited in the bore between the two (made it easy to make with just one hole bored straight through). The bearings are slightly preloaded with two locknuts on the spindle. I did intend getting a preload washer but they're not easy to buy as a one-off. It seems to work fine as it is.

Phil.
« Last Edit: June 17, 2017, 03:07:44 AM by philf »
Phil Fern
Location: Marple, Cheshire

Offline PekkaNF

  • Hero Member
  • *****
  • Posts: 1813
  • Country: fi
Re: Any advice on pressurizing (grinding) spindle?
« Reply #8 on: June 18, 2017, 05:21:02 AM »
Thank you Phil.

I tried to disaaseble the spindle, I see the bearing sizes, but dissambly is ont super easy. Everything is glued, even moderate heating does to work, have to heat it near 100C.

For set screw I had to modify allen key, 2,5  was way too loose, 3 mm or 7/64" would not go, I used diamond file to reduce 3 mm to 2,7 mm AF, hammered the key in, heated the spindle end to 65-100C and used pliers to crack open the set screw. You don't want to brak the set screw it is on alminium part and abuts agains spindle nose thread. Glued. Lovely.

After set screw is off the way, that aluminium shaft nut comes out easy with 17 mm AF spanner.

Spindle presses out from bearing housin easy.

There is a bearing nut inside the bell housing and that is glued and tight. Not off yet.


Offline PekkaNF

  • Hero Member
  • *****
  • Posts: 1813
  • Country: fi
Re: Any advice on pressurizing (grinding) spindle?
« Reply #9 on: June 18, 2017, 11:51:08 AM »
it needeed a got tightening on lathe tool holder from 43 mm circumfrence, application of heat gun on the castellated nut and a good grunt with a "special" tool + spanner. Bearings were finger tight on housing.

It had a liberal amount of green thread locker. Any recommendation? I don't want to go this tight again. Locktite 222?

Here are the pictures. It had some debris between bearings! And I could hear rought sound when I rotated them, nothing really agricultural wear, but clearly pasti it's prime.

Going to order some RS or RSL sealed bearings.

Pekka

Offline hanermo

  • Jr. Member
  • **
  • Posts: 63
Re: Any advice on pressurizing (grinding) spindle?
« Reply #10 on: June 18, 2017, 12:54:27 PM »
 :hammer:

Pekka ... I have the perfect solution for You- in my non-humble opinion.

Nilos rings.
Google it.

They are zero-contact, non-contact, industrial labyrinth seals that are easy to apply and use, seals of zero friction and airtight, to an extent re:pressure.
And easy to apply, and cheap.
About 17 each, maybe less for your smaller size.
Can be bought one at a time.

Absent fancy methods/tools, you apply it, and run it in 24 hours.
It self laps to an airtight fit, non-contact after run-in.

One of the coolest, fanciest, cheap gadgets I know, along with .. other Greatest Stuff:
+ hi-res cheap optical encoders, and ..
+ optical encoder hw readers/readouts (35 kHz iirc) for 60 (import, runs on 220V or 110V, as-is. Great !.).
(+ NSK Spindles from Japan, but another price level (2-6k). Amazing. Tiny at 40 mm D. Noiseless. 400W, more than my Bp M head (1/2 hp). 30.000 rpm (-to 60.000 rpm.)

Afaik Nilos rings are a german product, made there.
I would also expect to distribute/sell Nilos rings here in Spain, if I actually start to sell components.

BTW...
If anyone knows where to get hi-res encoders 50.000 counts - 1/2 M counts, at reasonable prices, and preferably upto 4 Mhz (CSMIO-IP-S limits) speeds, or 4 revs/sec at 1 Mhz = 240 rpm... please help.
Currently the better encoders dont seem to provide prices on-line, and I am aiming for sub 150-200$ pricing in unit quantities.

These would be for secondary feeds into T&C grinders, etc. while aiming for modern higher-end industrial levels.
Ie to read via sw and use the actual real angles from very high resolution(=/= accuracy) rotary tables, displacement stages, etc.


Offline PekkaNF

  • Hero Member
  • *****
  • Posts: 1813
  • Country: fi
Re: Any advice on pressurizing (grinding) spindle?
« Reply #11 on: June 18, 2017, 01:33:03 PM »
HHH Hannu Humble Hammering :lol:

Have you ever used them sucesfully?

I have some and agree, they are pretty good, but you have to design them in. You just can't slap them in most of the time.

Here they would need some carefull modification, biggest issue is to make the shaft nut (that squeses the two bearings together) much thinner, the Nilos ring would seal to inner ring and interfere with clamp nut. Now this nut is aluminium and it would need thinning to make space for Nilos ring.

I did consider it and I'm reconsidering it, probably even enough to buy some more Nilos rings, always need some components at hand they are great to stack on see if they can be crammed in.

Thank you,
Pekka
« Last Edit: June 18, 2017, 02:50:43 PM by PekkaNF »

Offline hanermo

  • Jr. Member
  • **
  • Posts: 63
Re: Any advice on pressurizing (grinding) spindle?
« Reply #12 on: June 20, 2017, 09:35:20 AM »
I looked at the seals/nilos rings as a completely separate issue re: spindle.

Ie a separate component holding/positioning them re. shaft nuts, collars, etc.
Kind of like a cover, over the spindle, from which the spindle protrudes, and is then sealed by them.

Thus the cover does not really need any precision, any strength, or any mechanical properties, or any precision, for the tiny-force Nilos rings.
The mechanical solution is bolts, to spindle housing face ... but I think/suggest any suitable locktite-stuff of low strength is probably better.

Probably, even any diy glue of low strength is ideal, easy to remove with hot-air gun, cheap.
Any collar, cone, taper, shaft surface can be used to align stuff, well enough, imho.
After all, You are probably never going to remove the cover, in your lifetime ... and if You do, or someone else needs to, they can always align stuff in a 4-jaw well enough.

As a reductio ad absurdum, a 1 mm thermoplastic, hot-air gun, hand pressure, would likely be fine, as a cover, and the rings slipped on after, glued in, lapped in.
(maybe a temp washer on the spindle, to create a tiny air-gap. Anything, really, from a 40 mm washer to a felt ring - grin).
These type of things have lowered hdd costs, machine tool costs, appliance costs, electronics costs, etc. 100-200x in 15 years.
Everything is small, light, cheap, plastic  .. lasts forever .. but is hard to repair/fix/unmount.

Maybe .. If you want to have access to the nut in front, make a larger collar, 2 mm thick, in any metal of you choice..
Use the (bigger) nilos rings to seal to that.
Allows unmount options later.
I would prefer zero nuts at front, drawn in from back via screws, bolts, bellevilles/springs/whatever.

Offline PekkaNF

  • Hero Member
  • *****
  • Posts: 1813
  • Country: fi
Re: Any advice on pressurizing (grinding) spindle?
« Reply #13 on: June 20, 2017, 10:17:49 AM »
Ordered some Nilos rings that looks about right with the bearings. They haven't left the Germany yet, looks like it's not going get fixed this week.

I think that Nilos rings should be pretty concentric and on the same plane with the bearing: After all they wear a small grove into bearing ring. Best mounted into same seat with bearing.

However, while I was playing with the bearings I noticed that they were noticeably magnetic! I.E. when soft iron was bought into contact with bearing it would stick to it. Wonder if that explains the bearings affinity to black iron muck? It has pretty big ferrite magnets.

Pekka