Appendix B - Safety Information - Renishaw RLI20-P User Manual

12 Safety information
Appendix B – Safety information
General
The RLI20 is designed for integration into the primary position
feedback loop of a motion system. It is essential that the system
is installed in accordance with the instructions in the installation
manuals. It is the responsibility of the system integrator to
ensure that, in the event of a failure of any part of the RLI20, the
motion system remains safe.
In motion systems with powers or speeds capable of causing
injury, safety protection measures must be included in the
design. It is recommended that satisfactory operation of these
protection measures is verified before the feedback loop
is closed. The following are examples of safety protection
measures that can be used. It is the sole responsibility of the
system integrator to select appropriate measures for their
application.
1. The RLI20 includes an error signal output. The control
system must be designed to stop the axis motion if this error
is asserted.
2. The axis must include physical limit switches which, when
tripped, will stop axis motion before damage occurs (soft
limits alone are insufficient).
3. Motor torque monitoring. If the motor torque exceeds an
expected limit, the axis of motion must be stopped.
4. The machine must include an emergency stop button.
5. 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.
6. Guards, viewing windows, covers and interlocks may be
used to prevent user access to hazardous areas, and to
contain ejected parts and materials.
7. 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.
8. 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.
For further advice, consult the appropriate machinery safety
standards.