Westwind Air bearing spindles... Need help

[Monk77]

Hi people

I'm exploring into Westwind Air bearing spindle repair and I'm totally clueless about how to go about it. Can anyone help?

[bigcatdairy]

sorry~seems nope~:P

[sanjiv]

pl. load some photos of defective spindle

[Monk77]

Hi all

The common defect is the jammed shaft of the spindle, caused by the mini holes inside the front air bearing blocked with dirt. I'm currently cleaing the air holes with a very fine guitar string, followed by using an ultra sonic cleaning device to clean up the surface.

But as I'm dealing with precision drilling process (FYI, I'm in the PCB manufacturing industry), the torque of the set screws that is used to tighten back the air bearing is quite critical. Can anyone help me on how much torque to apply here?
I'm having these few westwind models like M320-24, D1201-06 and D1331-26.

[bigcatdairy]

Is Here Anybody Can Tell Me What's Air Bearing?

[Monk77]

Hi

For what I understand, air bearing's application here is the same as the mechanical bearings. The only difference is the ball bearings are substituted by the air pockets for the air bearings. Do correct me if I'm wrong.
Can anyone help me on my previous posts?

[NEATman]

Monk77-
I have been designing air bearings for over ten years, although I have never disassembled a Westwind. The design you are describing is a common orifice type air bearing. I am assuming that you are using an air dryer and at least a 5-micron air filter to ensure that the air entering the bearing stays clean. I have worked on bearings that were 40 years old, and were still in great working condition - provided they are always supplied clean air. Be sure that oil and water aren't gathering in the lines. Does it usually only plug the lowest restrictors in the spindle? If so, it may be a liquid entering as a mist, and solidifying on the restrictors. A coalescing air filter installed before each spindle should help with this problem. If these are air turbine driven spindles, there may be separate inlets for the bearing and the turbine. If so, the bearing inlet is the more critical input. The turbine should be more resilient to small particles and mist.
Your cleaning procedure sounds good, but you should draw a vacuum on the supply port to draw out the particles that you are pushing back into the air passages, otherwise, they will just plug the holes again when you turn the air back on. After cleaning the hole with a fine wire, blow air back through the restrictor, while the vacuum is on. If this still doesn't work, you may need to send the spindle back to westwind for service. Most likely, they would remove the restrictors, clean and replace them - if their design allows that serviceability.
I can't offer any advice on the setscrew torque - it all depends on which setscrews you are talking about. There may be some that are tapped into the rotating shaft - these are probably used for balancing - DON"T MOVE THESE! Even a tiny imbalance at these speeds can ruin the bearing.

We sell air-bearing spindles with brushless motors, and they have a diamond like coating on the surfaces, which makes them crash proof. We still have a tight requirement on the supply air so that the holes don't get plugged, but even if they do get plugged, we can service them. We offer spindles up to 20,000 RPM with this type of brushless motor. We don't usually offer them for use as PCB drilling spindles however.

Bigcatdairy-
The easiest way to describe air bearings is think of an air hockey table. The air flowing out of the holes separates the puck from the table, so the only remaining friction is the air resistance of the puck and the slight viscous drag of the air under the puck. On properly designed air bearings, one square inch can support about 25-30 pounds at 60-PSI inlet pressure. The gaps in this type of bearing are about .0002" to .0005".
Here is a very informative website (not where I work) that discusses all of the different styles of bearings, and what is required for air filtration.
http://www.newwayairbearings.com/designinfo.asp#

NEATman

[ImanCarrot]

worked on bearings that were 40 years old, and were still in great working condition - provided they are always supplied clean air.

Well said- also, if you have a compressor resevoir before the filters then remember to empty the water out every day as this condensed water can fill the resevoir up.

[Monk77]

Hi guys

Currently I've this La-man filter system plus a 5 micron filter element at the incoming air supply so I'm very comfortable about the quality of the comp air here. FYI, I using a frequency convertor driven spindle and not a turbine driven one.

The screws I'm talking here is for tightening the front air bearings and I do not have any idea how much torque to apply when tightening them and the source of these blocked air pockets in the air bearings is caused by the by-product PCB 'dust' from the drilling and routing process... something like the wood chips flying off when using a bench drill.
I've a vacuum system in place to suck in all this 'dust' in but it seems that a small quantity managed to get past the dust cover and entered the bearing through minute holes and this cause the whole shaft to seize.

[bigcatdairy]

thanks guys!