General construction notes

Rotary axis

When designing high-speed rotary axes with main spindle function, it is important to consider the entire table in relation to the axis of rotation. AXRY-NGS (NGS-SBI) bearings are guided in rotation over the radial raceway, which thus forms the axis of rotation of the system. The eccentricity of all mounted parts should be kept as low as possible around this axis of rotation in order to ensure radial runout on the one hand, but also to avoid vibrations during operation.

Positive-locking centring of the connection parts such as for example the rotor on direct drives substantially reduces this problem.

Form-fit multiple centring via the bearing bore should be avoided, as this can distort the bearing and lead to increased friction torques.

Bearing preload

The bearings are radially and axially play-free and preloaded after assembly and complete bolting.

Temperature difference shaft / housing

The temperature difference between the shaft and the housing influences the preload in the radial part of the bearing. This must therefore be considered in the design for all operating conditions.

The temperature difference is application-specific and can only be simulated on test benches to a certain extent.

If the shaft temperature is higher, the preload in the radial part increases. This leads to higher friction, surface pressure in the bearing and to a lower life time.

If the housing temperature is higher, the preload in the radial part is reduced and the radial rigidity is also reduced. Any bearing backlash causes wear through slippage and loud noises.

If the temperature difference across all operating conditions is known, the radial preload can be adapted at the factory (customer-specific suffix Jxxxx).

Compensating for shafts which expand by adjusting clearance fits to the bearing hole is only useful if a Form-fit connection between the bearing and the shaft of the rotating axis is guaranteed for the intended operating condition.

Cooling

An efficient cooling system makes it possible to set an operating temperature with less fluctuations.

A separately-controllable cooling of the inner and outer rings is generally helpful.

Use the sensor hole provided in the bearing to monitor the operating temperature.

At high speeds and long duty-cycles, controlled cooling of the stationary and rotating components is strongly recommended to limit the temperature differences between the bearing inner and outer rings!

Contact our myonic application engineering department to specify the cooling system.

Cooling inner ring rotation

Cooling outer ring rotation

Unbalance / eccentric loads

Eccentric components generate high additional forces on the bearing. This can result in high vibrations, especially with high-speed axes. It is recommended to use automatic unbalance correction systems and to limit the residual unbalance of the workpiece to avoid premature bearing failures.

Eccentrically-applied operating loads have a similar effect.