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Donnerstag 23.03.2017
AeroLas GmbH
Grimmerweg 6
D-82008 Unterhaching
Tel.: +49 89-66 60 89-0
Fax: +49 89-66 60 89-55
Comparison of air bearing technologies
Air bearings (aerostatic bearings) belong to slide bearings. The pressured air within the bearing gap between the moved parts is the lubricant. The air cushion carries the load without any contact between the moved parts. Normally, the compressed air is supplied by a compressor. A key goal of supplying the air pressure in the gap is that the stiffness and damping of the air cushion reaches the highest possible level. In addition air consumption and uniformity of air supply into the gap are crucial for the behaviors of air bearings.
AeroLas´ innovative air bearings with highest performance
A high amount of specific laser-drilled micro nozzles is the stand-out feature of AeroLas’ innovative air bearings. The dead volume of our air bearings nearly disappears compared to all other air bearings. Accurate calculations ensure the perfect amount, distribution, and geometry of the micro nozzles. In doing so, we perfectly adjust our air bearings behaviors to the customer’s needs. As for the high amount of micro nozzles, there is an unlimited number of variations between the static and dynamic features possible. These improvements in the air bearing technology, make AeroLas unique in the world. In addition, AeroLas’ technology allows solutions, even for industries other than the classical air bearing ones as substitutes for roller/friction bearings, possible.
Design of a typical
conventional air bearing
Conventional air bearings
At conventional single nozzle air bearings the compressed air flows through only a few but relatively large nozzles (diameter 0.1 – 0.5 mm) into the bearing gap. The air consumption thus allows only some flexibility such that the bearing’s features (force, moments, bearing surface, bearing gap height, damping) can be adjusted only insufficiently. However, in order to allow a uniform air pressure even with only some nozzles, air bearing manufacturers take constructive techniques. In doing so, these air bearings cause dead volumes (non-compressible and thus weak air volume). In effect, this dead volume is tremendously harmful for the air bearing’s dynamic and causes self-excited vibrations.
Single-nozzle air bearing
with pre-pressure chamber
Single-nozzle air bearings with a pre-pressure chamber consist of a chamber around the centralized nozzle. Usually, this camber’s ratio is between 3 % and 20 % of the bearing’s surface. Even with a chamber depth of some 1/100 mm, the dead volume is very high. In worst case these air bearings consist, instead of a chamber, a concave bearing surface. Besides other disadvantages, these air bearings demonstrate, in particular, a very poor tilt stiffness.
Conventional air bearing
with micro channels
Typical, conventional air bearings are implemented with chambers and canals. This design assumes that with a limited amount of nozzles, the dead volume should decrease while distributing the air within the gap uniformly. Most constructive ideas refer to special canal structures. Since the late 80s, air bearings with micro canal structures without chambers are manufactured. However, also this technique has to get along with problems with dead volume. When looking at the air bearing technology of AeroLas, it is proven that: With an increasing gap height, the micro canal’s load and stiffness decreases. As in the case of high-speed linear drives or high-frequency spindles, the mentioned may cause serious disadvantages.
Sintered air bearings with
porous material
So-called sintered air bearings made out of porous material should allow a uniform air distribution. Disadvantages are the high dead volume (cavities in the material) and the unequal outflow of air due to a non-uniform porosity. Moreover, fluctuations of the bearing’s behaviors must be taken into account. Depending on the system, sintered air bearings are only recommended for temperatures between 0° and 50° Celsius.
Air Bearing Technology
exact calculations
customer´s benefit
performance comparison