[Zathras]

Hi guys,

I'm looking for some disk or "pad" air bearings for an application I have in mind. None on eBay at the mo!
I've tried New Way to get an idea what air bearings might cost but they didn't bother answering my quote request.

I have requested a quote from "Specialty Components" but just wanted to ask if anyone has dealt with their air bearings before;
http://www.specialtycomponents.com/nf/linear.htm

Are there any (relatively) cheap alternative manufacturers that you know of?

I'm not that hopeful that they will be affordable (I'll need 12) so I wonder if I would be able to make something like this;
[ame="http://www.youtube.com/watch?v=YhOUuxPq3Gk"]YouTube - Laser cut air bearing[/ame]

OK, maybe they won't be quite up to the commercial stuff but might be worth a try. What do you think?


Thanks!

[McNeillMachine]

I've used New Way bearings in the past. Good stuff. I had a 90lb carriage that I could push back and forth with 1 finger... IIRC the cost was about 150-200 dollars each depending on size. The mounting hardware will add up, too. You'll also need a dry air supply to run them.

Hope that helps.

[Zathras]

McNeillMachine,

Yes that helps thank you! The New Way ones do look very nice.
Sadly I've received no answer from either of the manufacturers but at least now I know roughly what I would be expecting.
That's not too bad a price as I was expecting something like $250 upwards.
I'll still have to try and get a hold of Slocum's book and have a look at the chapter on air bearings.
The way things are going, I'll have to look at the feasibility of making them anyway.
So many RFQs gone unanswered!


Thanks again.

[McNeillMachine]

I haven't heard of Slocum's book. What's the title? It might not be a textbook, but there's a pretty good tutorial on air bearing usage on the New Way website. It covers many applications.

I didn't buy direct from the manufacturer when I got my bearings from NW. Your tag says Australia - If I were you, I'd try to find a distributor locally. Anyone that sells automation and motion control parts could probably point you in the right direction.


-Phil

[Zathras]

Phil,

Here 'tis;
[ame="http://www.amazon.com/Precision-Machine-Design-Alexander-Slocum/dp/0872634922"]Amazon.com: Precision Machine Design: Alexander H. Slocum: Books[/ame]

I've read that Slocum's book has some great info on air bearings. I believe this is the one. I'm hoping the book will give me enough insight into their design to assess weather it's even possible to build one, my guess is no but I'll at least look. It may be more effort than it's worth in the end, dunno.
As an aside I did find a manufacturer here that makes porous ceramics in discs, tubes and plates. That might be useful later.

I did ask the manufacturers if they had local distributers here. On the other hand, some distributers here tend to hike the pricing way up and it's not even worth getting some items here.
I will try your suggestion though by going to some motion control resellers.


Thanks,
Mark

[holbieone]

http://www.airfloat.com/how_airbearings_work.php

[holbieone]

http://www.olympus-controls.com/pdf/...gn%20Guide.pdf

[Zathras]

Thanks for the links guys. The New Way doc seems quite useful!
As for looking into the design of air bearings, I've been trying to find more precise technical details such as dimensions of groove layouts and hole diameters.

At least I know the sort of dimensions we are talking about from this paper:
http://www.nsc.co.jp/en/tech/report/pdf/n9304.pdf

Just to summarize the main dimensions;

Central Hole diameter: 0.2mm
Groove (channel) depth: 10 - 40 micron
Groove width: 1mm
Height above surface: 3 - 7 micron
Bearing dimension: 40 x 40 mm

Assuming these are fairly typical dimensions for such bearings, it's just not viable for home made gear!
OK, no where else to go but the next step.
There are several alternatives I can think of to try and cheat a bit;

Porous media bearings;
1. Porous Carbon (Hard to find a source!)
2. Porous Plastic (Don't think it would work ?)

Machining a disc face using;
1. Laser Etching
2. Photochemical Etching
3. Electrochemical Etching
4. Ultrasonic machining

Or perhaps instead of machining a disk directly, just a s/steel thin round sheet and mold around a body of epoxy?
Or maybe use it as a kind of template for a molding process? (Maybe a negative will be required.) That way cost could be minimized by having one master.


Any thoughts? (Apart from you are crazy!)

[NEATman]

Zatharas-
I've designed air bearings for over 10 years for three different companies in Southern New Hampshire and Northern Massachusetts. What exactly are you trying to build? The video that you show is either a magnetically preloaded air bearing (most likely, as it only has one tube) or a vacuum preloaded air bearing (typically have two tubes, one vacuum one positive pressure).

There is also Nelson Air Bearings: http://www.nelsonair.com/ They do list a new-way style puck. They are also a smaller company, and would probbably be willing to sell to an individual. They are probbably your best bet.

You may want to contact ABTech (smaller company, I know that they have built small pucks in the past, but don't show them on thier website) http://www.abtechmfg.com/index.html

I know that Dover makes thier own restrictor style pucks, but they don't sell them individually as new way does. http://www.dovermotion.com/

What I know about new way bearing is that the porous carbon is a grade of die-sink EDM material. I never did find out the exact grade, but you could experiment. The main problem with air bearings is when you have too much flow. Something called pneumatic hammer will occur, which is when the air bearing puck begins to vibrate when the flow is too great. In effect what causes this is when pressure builds up under the puck, lifts it to too great of a height (about .0015-.002" or more) and then due to the "large" gap, it exhausts quickly causing the puck to rapidly loose height. This cycle then repeats, and you get a bad vibration. The best air bearing gap (depending on the design) is between .0002" and .0006". Getting this flow rate correct is challenging. If you find the proper porous graphite material, you could litterally make the pucks with a basic lathe, epoxy and a piece of fine sandpaper on a good flat surface (granite plate or a piece of float glass). You could try some EDM graphite like this:
http://cgi.ebay.com/5-lbs-Hi-Grade-G...QQcmdZViewItem

I would also strongly reccomend that you stick with the individual self-aligning pucks as they are very forgiving and the restrictor style flat plates and spindle style bearings are ground to about .00005" flat per square inch. Some of the best spindles have shafts that are .00001" max. out of round, and the air bearing gap will average out these slight errors, and you end up getting a bearing that has 1 millionth of an inch axial and radial runout.

As a rule of thumb, you should get about 30lbs load capacity per square inch of air bearing area with the bearing connected to a 60 PSI source.

Good luck with your project. Let me know if I can be of any more assistance.

I'll also have to look around, as I think I may have about 6 or 8 Ø2.5" new way pucks around here somewhere.

Regards,
NEATman

[Zathras]

NEATman,

Whoohoo! I hit the jackpot with an expert here.:rainfro: Some great advice thank you!!

Well Neatman, you're gonna think I'm crazy but I would love to build a small grinder to rough some optics! Being and amateur astronomer I would at least wanna try to see if I can do it. Still need an air bearing block and air bearing grinder spindle. Prob get some Granite blocks for the base if I can find a cheap-ish source or some chunky glass block. Should be fun trying.

The gentleman that produced that bearing in the link states that it is magnetically preloaded with a plate of metal behind the acrylic sheet he's holding. I'm sure it's quite bent under the weight so you see it sticking a bit when he's moving it.
BTW, I have written to him and asked if he is willing to show us his design. Worth a shot I thought.

Thanks for the advice in those companies. I did look at Nelson Air (they look nice) and was planing to RQF as soon as I can work out my needs.
I'd be guesstimating really but I think the FP-C-015 (http://www.nelsonair.com/NA_prods_flatpad.htm) should be ok.
I'll have to work out the approximate weight of the components based on the 30lb/in^2 you gave.
The bushing type looks interesting since the shafts would be easy to get or should I stick with the puck style like you said?

I do like (prefer) the porous bearings, in principle they seem easy to make. But the carbon is hard to get and probably very expensive. Thanks for the eBay link, looks interesting but again, dunno what you get for the money and freight here to Australia would double the cost. I'll think about that one though.

I appreciate you looking around in your boxes for those bearings Neatman. I'm sure we could come to some arrangement if you wish to sell them!

Regards,

Zathras

[NEATman]

Zatharas-
First, let me state that I am a packrat!

Second, you aren't crazy at all. I helped design a 5 axis grinder for glass lenses, now that was an awesome machine!

I found (7) 2.5 inch new way pucks. There are a couple scratches here and there, but they won't affect the performance. I also found (7) Dover 2.5" porous restrictor pucks, dimensionally the same as the New Way, and simmilar performance.

I'm glad you said you need a spindle, I happen to have (4) air bearing Dover spindles with 3 phase motors and encoders installed. I'd be willing to part with one.

I also have a small XY stage from Dover, but I plan on keeping that for use in making an extremely accurate mini-milling machine some day. Also, if I had more room, there was an old Pneumo diamond turning lathe that someone had in thier garage about 70 miles away - they put it on craigs list last week in hopes that someone would come get it for free and save them the hassle of having to transport it to the scrap yard!! Before I could comment, they deleted the listing, as I'm sure someone jumped on it! It was over 6000 lbs, so shipping to Australia would have been painful!

Depending on how you design your machine, there are tricks to magnetically preloading these bearings - even when using granite or glass. I can give you some pointers, and suggest magnetic designs and magnet sources (www.kjmagnetics.com).

Depending on the travel of your machine, I have a friend who has several Baldor linear motors he is looking to sell. Could make for an interesting machine...

Send me a private message, and we can talk via e-mail more privately. I can probbably dig up a solidworks model of the pucks, and perhaps make some design suggestions on the design of your machine if you are interested.

Regards,
NEATman

[New Way]

Hello Zatharas,

I am sorry to hear no one from New Way has replied back to you on your request for quote. If you would like to contact me and discuss you application in depth and see what we can offer you please do so, my contact information is:

Rich Hesse
Applications Engineer
610-494-6700 ex 210
New Way Air Bearings
[email protected]

Also we do not have a rep/dist in australia, you can contact me directly. If it is easier for you, you can also contact me through SKYPE, I have a few customers from australia that use this chat program, I have a labtop.

[cogsog]

Neatman, I am hoping you would know what type of epoxy is generaly used by nelson or New way.It is white...???
Cheers

[NEATman]

cogsog-
I sent you a PM.

Keith