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4. Motor torque monitoring. If the motor torque exceeds an expected limit, the axis of motion must
be stopped.
5. The machine must include an emergency stop button.
6. Following error detection. If the difference between the controller demand position and the axis
feedback position exceeds an expected limit, the axis motion must be stopped.
7. Guards, viewing windows, covers and interlocks may be used to prevent user access to
hazardous areas, and to contain ejected parts or materials.
8. If the machine includes an independent tacho (velocity) feedback system, this should be cross-
checked with the position feedback. For example, if the tacho indicates the axis is moving, but
the position feedback doesn't, the axis motion must be stopped.
9. In the case of synchronised parallel motion systems (for example twin rail gantry drive systems),
the relative positions of master and slave axes should be monitored. If the difference in their
positions exceeds an expected limit, axis motion must be stopped.
Important note: In the case of measures 6 to 9, the limits need to be selected carefully depending on
the application and the type of position compensation selected to avoid false alarms.
For further advice, consult the appropriate machinery safety standards.
Secondary fault protection measures
It is the responsibility of the system integrator to ensure that in the event of a failure of any part of the
Renishaw Laser System that the motion system remains safe. In the case of motion systems with
powers or speeds capable of causing injury, secondary protection measures must be included in the
design. Refer to the General Safety Information in the Introduction for details of suitable secondary
safety measures. It is recommended that such secondary measures be tested during system
integration by deliberately introducing single faults into the system. (Obviously such tests need to be
carried out carefully to ensure injury cannot occur if such secondary systems fail to operate)
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