the spindle would be the hardest part to make the air bearing for. you may
be able to get away with making several radial airbearings like what newway
sells http://www.newwayairbearings.com/catalog/radial-air-bearings-concave
when the flying distance is only 0.0002in you would need to hold a better
tolerance then that. Now that is making quality bearings to sell to places
like the semiconductor industry.so if you are making them yourself you
probably don't need as good of tolerances. if you did individual radial
bearings you could probably just use a piece of the final shaft as a lap to
bring the radius into spec. you then mount them on ball mounts like the
linear bearings and it should be doable.
Still not the easiest thing.
I has some random piece of aluminum. I think i am going to try making an
air bearing.
The limiting factor on the flow rate should be the sonic speed of the
compressed air. so getting a measured volume of air is actually easy to do
with an orifice. I am thinking the cross sectional area made up of the fly
height and the edge length of the bearing would function like an orifice of
the same cross sectional area. so taking the length and the height you want
to achieve and knowing the sonic speed of the air should give you the
amount of air needed. I will have to double check my fluids book and my
machine design notes but this should be a do able calculation. I think the
pressure under the bearing should remain fairly constant at the system
pressure.
if you switch working fluids to oil and did a closed system for the spindle
you probably don't need as tight of tolerances, and you could get higher
pressure. it would basically be like the high pressure jacking pump oil in
large industrial motors.
On Sun, Feb 7, 2016 at 11:48 AM, Simon Heath <icefoxen@xxxxxxxxx> wrote:
It's awesome to read all of this stuff and think that 150 years ago,
people were hand-turning screws and the idea of interchangable parts was a
miracle.
Also Andrew, he mentioned some name of a company that used to make that
design of chuck, we might be able to look it up.
Simon
On 2/7/2016 09:54, Andrew C. wrote:
Alex,
I know a little about air bearings. Just the surface stuff, but
definitely not in depth. I do know there has been at
least one article written for skilled home shop machinists on making an
air bearing spindle- I remember tolerances
of +/- 0.0002 mentioned on the walls. It is doable- but it is very very
difficult. At that point, you aren't machining anymore-
you are doing internal grinding work. Doable, but very challenging.
Normal people that aren't grinding specialists, without
the positioning equipment, would find it impossible. I don't think my
normal equipment could go quite that low to grind
accurately at that level. I could maybe do it with a hand graver, on a
very short area, but not with a large bearing and
grinding. That's beyond my ability. We'd need something like
zero-backlack ballscrews to position accurately for that.
Linear air bearings- I would love to learn more about those- don't
understand them at all. Only rotating ones somewhat.
2 things- that box in the background he has, with the 2 holes in it back
behind the window- that's a laser welder. He
is very very well equipped. Those are extremely expensive. Also- did you
notice he could zero the runout of his chuck
running on the air bearings? That's a feature of a collet chuck- except,
in a 4 Jaw. I would love to see how he made that
chuck- that is a very exotic ability for a normal chuck.
-Andrew
On Sat, Feb 6, 2016 at 11:03 PM, Alex Reasinger <alexreasinger@xxxxxxxxx
<mailto:alexreasinger@xxxxxxxxx>> wrote:
From what i have found they run at 60-80psi.
http://www.newwayairbearings.com/
The are only flying 5micron (0.0002in) about the other surface so
there is not much room for the air to compress.
The amount of deflection due to the compression of the air would
have to due with the amount of surface area. 60psi on a 1in by 2in
surface is 120 lbf and you would have more then one bearing per
surface.
Air bearing spindles are very common in high
precision applications. the runout of an air bearing is far better
then anything you can achieve with mechanical bearings. you can
run air bearing spindles at much higher speeds.
The tolerances for linear bearings would not be as bad as you may
think. If you mount them on a ball and socket mount you no longer
have to worry about the parallel and squareness of the overall
part. All you have to worry about is the bearing surface flatness
and finish. On a small part should be able to hand lap that.
Air bearings could be do able.
When i was working on my steam engine i was playing around with
the air and had the two parts acting like an air bearing.
I may need to start playing around with making an air bearing.
this could be fun.
On Sat, Feb 6, 2016 at 8:43 PM, Joachim Hall
<jjoachimhall@xxxxxxxxx <mailto:jjoachimhall@xxxxxxxxx>> wrote:
How much pressure do you supply to an air bearing? I would
think on a lathe spindle it would get pushed off center when
you start applying a cutting load and the surfaces would rub.
But I guess if you had enough air pressure...
-Joachim
On Sat, Feb 6, 2016 at 7:14 PM, Andrew C.
<soshumasamune@xxxxxxxxx <mailto:soshumasamune@xxxxxxxxx>> wrote:
Oh dear god, they finally found it. THE lathe.
Alex I knew you would find this. I didn't know how long it
would take, but yeah. This lathe is absolutely ridiculous.
I honestly don't think anyone at hack pittsburgh would
have any project needing 1 micron accuracy, but I want this
lathe, bad.
Air bearings though, are doable. They can be machined
yourself, but the tolerences are crazy tight, and they
have to be
dead on to work right. If you could do an air bearing
spindle for your lathe, that would be the ultimate-
100,000 RPM and
micro tiny parts at constant surface speed would be doable.
-Andrew
On Sat, Feb 6, 2016 at 3:21 PM, Joachim Hall
<jjoachimhall@xxxxxxxxx <mailto:jjoachimhall@xxxxxxxxx>>
wrote:
I've seen this video before! It amazes me every time.
It's amazing how all those parts are just floating on air.
On Feb 6, 2016 2:45 PM, "Alex Reasinger"
<alexreasinger@xxxxxxxxx
<mailto:alexreasinger@xxxxxxxxx>> wrote:
probably to much for hackPGH to buy, but it does
give me some inspiration for the lathe i am
working on.
I am now looking up epoxy granite and air bearings.
On Sat, Feb 6, 2016 at 2:39 PM, John Lewis
<oflameo2@xxxxxxxxx <mailto:oflameo2@xxxxxxxxx>>
wrote:
I'm interested. How much would it be?
On 02/06/2016 02:27 PM, Alex Reasinger wrote:
> https://youtu.be/sFrVdoOhu1Q
