Automatic relubrication and bearing condition monitoring
22 February 2016
Precision bearing manufacturer Schaeffler has introduced its fifth generation of linear recirculating roller bearing and guideway assemblies. The RUE-E series now includes sensor units that provide both automatic relubrication and bearing condition monitoring.
Where necessary, the sensors monitoring the condition of the lubricant send a message to the machine control system, initiating automatic relubrication via, for example, Schaeffler’s FAG CONCEPT8 multi-point lubrication system. In order to monitor the condition of the bearing, a piezoelectric accelerometer is mounted to the steel saddle plate on the carriage. This provides the vibration velocity, vibration acceleration and rolling bearing parameters to the attached signal converter, as well as monitoring the pre-set limit values.
The system provides users with direct feedback and communication with the unit’s control system, automated lubrication where necessary and automated maintenance. Manual lubrication is no longer necessary and lubricant use can be reduced by up to 30%. Automated condition monitoring provides predictive maintenance which, in turn, increases availability and quality, as well as reducing total cost of ownership.
In its as-delivered condition or when a linear roller bearing and guideway assembly is used in a feed spindle, the guideways are generally in optimum condition with regards to their running characteristics and lubricant condition. This can be seen through the vibration behaviour of the saddle plate when the system is in motion. In order to establish variations and deviations from this ideal nominal value, piezoelectric accelerometers are mounted to the steel saddle plate on the guideway carriage. The accelerometers are suitable for use with coolants and in harsh, contaminated environments. The permanently connected, two-wire, separately shielded cable is completely encased in polyurethane. The sensor has a sensitivity of 100mV/g, a resolution of 0.001g and a frequency range of 5000 to 50,000Hz for measuring energy spikes.
The accelerometer measures vibration velocity, vibration acceleration and provides rolling bearing parameters to the attached signal converter via the cable, as well as monitoring the pre-set limit values. The signals are then separated into different frequency ranges or an energy evaluation of the impulse peaks is carried out using spike energy (gSE). 4-20mA and 0-10V signals are passed to the PLC, the Schaeffler Box (controller) and the lubrication unit via analogue outputs. This closes the loop between the monitoring and automated lubrication.
The FAG CONCEPT8 multi-point lubricator is an integral part of the lubrication control loop. This lubrication system for rolling bearings ensures that optimum lubricant is fed to the bearings without the need for any manual intervention. If the actual evaluated signal values sent by the signal converter deviate from the nominal (pre-set) values, FAG CONCEPT8 automatically ensures appropriate maintenance measures or relubrication are initiated.