Description of Functions
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EN
· 30.30.01.02851 · 01 · 03/22
7.25.2
Predictive Maintenance (PM)
Overview of Predictive Maintenance (PM)
In order to allow early detection of wear and other impairments to the vacuum gripping system, the ejector provides
functions for recognizing trends in the quality and performance of the system. This is accomplished using the
measured values for leakage and dynamic pressure.
The measurement value for the leakage rate and the related quality assessment in percent are reset at the start of
every suction cycle and constantly updated during the cycle as moving averages. The values therefore remain stable
until after the suction cycle is complete.
Measurement of Leakage
The control function interrupts suction as soon as it reaches the limit value SP1. Then the leakage is measured as the
vacuum decrease over time (in mbar/s).
Dynamic Pressure Measurement
This measures the system vacuum achieved during unobstructed suction. The measurement length is approx. 1 s. Thus
evaluation of a valid dynamic pressure value requires at least one second of unobstructed suction after the suction
cycle has commenced. The suction point must not be occupied by a component at this time.
Measured values below 5 mbar or above the limit value SP1 are not regarded as valid dynamic pressure
measurements and are discarded. The result of the last valid measurement is retained.
Measured values that are below the limit value SP1 but simultaneously above the limit value SP2 – rP2 result in a
condition monitoring event.
The dynamic pressure and the performance value in percent based on it are initially unknown when the area gripper is
switched on. As soon as a dynamic pressure measurement can be performed, the dynamic pressure and the
performance evaluation are updated and retain their values until the next dynamic pressure measurement.
Quality Assessment [0x00A2]
In order to evaluate the entire gripping system, the gripper calculates a quality rating based on the measured system
leakage.
The greater the leakage in the system, the worse the quality rating of the gripping system. Conversely, low leakage
results in a high quality rating.
Performance Calculation [0x00A3]
The performance calculation helps in evaluating the system status. The performance of the gripping system can be
assessed based on the measurement of the dynamic pressure.
Optimal configuration of gripping systems leads to low dynamic pressure and thus to high performance. Conversely,
badly configured systems achieve low performance.
Dynamic pressure events that exceed the limit value (SP2 – rP2) always result in a performance rating of zero percent.
A dynamic pressure value of 0 mbar (which indicates that no valid measurement value could be obtained) also results
in a performance rating of zero percent.
