Flat Round Air Bearing Installation and Adjustment

New Way Air Bearings’ products provide exceptional flatness and parallelism, but in order to achieve the specifications listed on our product pages, all New Way products must be placed and installed directly against a precision ground guide surface. Before any measurements are taken, the surfaces should be cleaned in accordance with our Care and Air guidelines, namely using 70% isopropyl alcohol only.

Surface Flatness Requirements for Flat Bearings

Per our Application and Design Guide, we recommend a surface finish of 16 RMS or better. Local flatness, which we define as the flatness under the bearing at any one time, should always remain below 50% of the designed air gap. This is a worst case scenario, and it is relatively easy to stay within 10% of the air gap height.

For instructions on how to appropriately measure flatness, parallelism and height of our air bearing products, please refer to the instructions on this page, as they will be utilized in the setup of your new air bearing systems.

There are two primary methods by which flat round or rectangular bearings can be established in coplanarity; displacement measurement or vacuum replication.

Displacement Measurement

This method uses a dial indicator to measure the fly height of the bearings. We recommend this procedure as an extra level of validation for setting up single bearings, and as a first option for setting up bearings which must be coplanar.

Select an indicator and stand which will allow you to get the indicator tip on the back of the bearing to be checked. The indicator must have a minimum resolution of one micron or 50 microinches to be useful in this checking procedure. Mechanical indicators with this level of resolution are readily available. Electronic indicators are available with 0.1 micron or 5 microinch resolution, and capacitance probes may also be employed, with resolution down to 0.01 micron of 0.5 microinch, although we feel mechanical indicators are quite well suited for testing fly height and preload adjustment. Electronic indicators are preferred due to their increased resolution and remote reading capability, but are not necessary, and capacitance probes, while the most accurate, are overkill unless you are performing a dynamic study, in which their noncontact nature makes them the preferred choice.

With the preload bearing tightened, position the indicator tip on the back of the bearings about 5mm (0.25 in) from the edge of the ball socket. With the air pressure turned off, zero the indicator, then turn the air pressure back on and read the indicator. Turn the air pressure back off and see if the reading returns to zero. If it does not return to zero, repeat the process until consistent readings are achieved. It is not unusual for technicians to overtighten the preload bearings (with pressure off) to help seat the ball studs in their sockets. This can result in more consistent readings and provide for a marginal gain in system stiffness. Finally, compare the displacement measurements to the design fly heights, and adjust the preload bearing accordingly such that both bearings read an identical fly height.

Vacuum Replication

Vacuum replication is our recommended process for achieving coplanarity between multiple air bearings. Due to the squeeze film effect inherent to porous media compensation, the fluid layer underneath the bearing is stiffer than the all metal structure which houses the bearing. We may take advantage of this by running the air line to the bearings in reverse, applying a vacuum which secures the bearings to the guide face. First, secure the bearings to their supporting structure by use of threaded ball screws, which allow for the bearings to pivot relative to the support structure.

Next, apply vacuum on the bearings such that they are replicated to the guide surface. Once the bearings are secure, level the the support structure by use of the threaded ball mounts, and any other adjustment points which may be built into the system. Once this is accomplished, switch the bearings from vacuum to positive pressure, and re-measure the system for planarity.