Linear air bearings

Linear air bearings

Linear air bearings

Keywords: Activators, Automation

An aluminium beam and porous air pucks combine to solve the problem of getting linear air bearing motors into general production applications.

Anorad, a subsidiary of Rockwell Automation has unveiled an air bearing linear axis that is suitable for general production environments. The air bearing beam uses an extruded aluminium beam rather than conventional granite and is seen as a major breakthrough in price and performance that opens up new technology for broader automation use (Plate 6).

Plate 6 Anorad, a subsidiary of Rockwell Automation has unveiled an air bearing linear axis that is suitable for general production environments

The linear air bearing gives many benefits to the user, including, because of the fact that none of the moving parts are in contact with each other, almost zero maintenance and hence very low cost of ownership. Other benefits include high throughout because of its speed, high accuracy and repeatability, low current consumption, exceptional velocity control and easy fixing.

Anorad's fundamental innovation is an extruded aluminium beam that creates the platform for the linear motor. The design delivers rigidity and stiffness with repeatability in the order of a few microns, incredible velocity stability of less than 1 per cent deviation and the ability to carry a payload up to 15 kg at 3 m/sec with 2G acceleration.

The worst enemy of traditional air bearings are small particles which can become trapped and literally grind away the beam's surface. Anorad's solution has been to design a puck that is slightly porous, allowing tiny particles to effectively be absorbed into the pores thereby removing their ability to affect the beam surface.

The first aluminium air bearing beam produced by Anorad has a 2 m travel and its applications include digital printing machines, packaging equipment, inspection machines, bio- medical and general semiconductor applications – in fact the air bearing assembly can be used anywhere from clean room to general industrial environments.

The motor has an epoxy core (ironless) design and feedback accuracy comes from a linear optical encoder. Excellent bearing preload gives both stability and stiffness in the system. Because the air-bearing beam is effectively commutated as a brushless servomotor, any number of amplifiers and motion controller are compatible with it.