The accuracy of the path traveled by a bushing is determined almost entirely by the accuracy of the guide.

Two common methods for mounting air bushings in a standard New Way mounting block or bore in a custom housing are:

O-Ring press fit (flexible mount).
Standard New Way air bushings are supplied with 4 o-rings, two inner and 2 outer rings. The two inner o-rings form a seal to allow the pressurized air to supply the air bearing. An air supply hole can be located anywhere on the mounting block between the two inner o-rings. This mounting method allows the air bushing to “float” somewhat in the housing to allow the air bushing to align axially with the shaft and accommodate misalignments of air bushings and shafting of up to .002” (.050 mm).  Install the two outer o-rings for a flexible mount with additional stiffness. Use Isopropyl Alcohol as a lubricant when pressing the bushings into a mounting block or housing.

Bonded in place (hard mount).
This method requires the use of 4 o-rings. The inner two o-rings form the seal for the air supply. The outer two o-rings form two annular cavities with the inner two o-rings. These cavities are filled with an epoxy that will fix the air bushings in precise alignment with the shaft. In this method, the air bushings are positioned in the housing with the 4 o-rings. Again, use Isopropyl Alcohol as a lubricant before pressing the bushings into a mounting block or housing. Align the shafts and supply compressed air to the air bushing via the supply hole located between the inner o-rings. The epoxy is then injected though holes in the housing so that the cavities between the outer and inner o-rings are filled. The air supply to the air bushing must remain on while the epoxy cures. If custom housings are used, be sure to supply an additional hole in the cavities so that the air can escape when the epoxy is injected.

We recommend using 2-part epoxies that cure completely without special additional catalysts, have good bond strength to metals, and can readily be found in viscosities that lend them to this application.  Shrinkage is typically not a concern in bonding air bushings in mounting blocks. Other properties such as out-gassing should be considered depending on the environment where the air bushings will be located. Most epoxies cure exothermally but with the amount needed to bond the air bushings, this should not be a concern.

Specifically the recommended characteristics are:

1. A room-temperature cure epoxy with a reasonable set-up time or pot life for the number of air bushings being bonded – recommend 30 to 120 minutes.
2. A cure time reasonable for the application – recommend 24 hours.
3. A viscosity that lends itself to injecting into the hole provided in the pillow block or mounting block – recommend between 5,000 and 100,000 cP (centipoise).

New Way recommends using DWH-310FL Static Fitting Material manufactured by Moglice (see link below) for this application.

Reference: www.moglice.com

The simple answer is yes, but we preface this with the statement that New Way air bushings are not tested specifically for high rotary speeds like an air bearing spindle. Through some cautious trial and error, you can safely test the operation of a New Way air bushing in your desired speed range.

The initial problem to solve will be selecting a coupling for the air bushing shaft that does not introduce any error motion from your driver due to the belt or motor's axis of rotation error, and/or vibration. A "Google" search on "Helical" or "Bellows couplings" will provide many options for couplings.

The air bushings include O-rings that allow the air bushing to be press-fit into a New Way mounting block - this will provide some compliance to mitigate this problem. (Remember to use Isopropyl Alcohol to lubricate the O-rings, before you press the bushings into the pillow blocks!)

Once the coupling is selected, and the air bushing is operated like an air bearing spindle, you may discover some heat build-up at around 50 meters-per-second (170 ft/s or 40,000 rpm for a 25mm OD shaft), due to the viscous shear of the air film between the air bushing and the shaft. You may actually need to grind the shaft down below the New Way recommended diameter in order to accommodate shaft diameter growth due to thermal expansion.

The heat gain is partly offset by the cooling of the air input into the air bushing, so it is difficult to predict when you will need to address the dimensional changes. Our suggestion is to incrementally increase the rotational speed by 7 meters per second (22 ft per sec or 5000 rpm with a 25mm shaft), until you begin to see a change. Since the air bushing is virtually frictionless, a good indicator is when changes in the current draw of your motor becomes non-linear.

As heat builds, the shaft will grow and displace the air film within the air bushing, and can come into contact with the Porous Carbon media. The air bushing should not be damaged, as long as the shaft finish is per the New Way recommendation (Ra 0.4mm, 16µ in) and the period of contact is brief; on the order of a few minutes.  Let the shaft cool before trying to remove it from the air bushing.

Recommended Bushing Rotary Speeds: (50 m/s  -  170 ft/s)

Bushing ID  Speed (Rpm's)

0.25 Inch   140,000
13 mm        76,500
20 mm        50,000
25 mm        40,000
40 mm        25,000
50 mm        20,000
75 mm        13,250

If you need further assistance, please contact New Way Air Bearings.

Radial (normal) stiffness is measured with the bushing flying on a shaft of the dimension specified with the specified air pressure applied. A known mass is suspended from the bushing housing (without a pillow block) and the displacement is measured several times and averaged.

Pitch moment stiffness is measured with the bushing flying on a shaft of the dimension specified with the specified air pressure applied. The bushing is mounted in a pillow block and equal and opposite moment loads are applied at equidistant points from the center of the bushing.  The displacement is measured and the stiffness is calculated using the known force applied.