Light Curtain

What is the best way to disable a single axis when a light curtain is broken? Can this be done over ethernet, or do I need to add a digital input module?

My safety relay is interrupting power to the directional control valve, but I don’t want to the RMC’s control output to saturate while the curtain is broken and cause the axis to take off uncontrollably when the curtain is cleared.

I’m still in the design stage on this project; just trying to decide if I need to make hardware accomodations for this situation.

You can do this over Ethernet. Send the Enable/Disable Axis (97) command to disable an individual axis.

Since this is a safety question I will expand more.

I would prefer to use a digital input that must be energized to keep running. The circuit can then be de-energized by the light curtain, loss of power, an e-stop button, loss of hydraulics or any other reason that you can think of that should de energize the input.

De-energizing the RMC input is only one step. The blocking valves that allow oil to flow should also be de-energized so there is a hydraulic lock on the oil flow and nothing will move. Simply de-energizing the RMC does not guarantee that the motion will stop. There can be leaky valves so that even if the RMCs output goes to 0 the actuator will still more. Also, if this is a press, it will settle due to gravity eventually.

For maintenance I suggest a mechanical block or hook. I have some customers that have hooks that keep the actuator and machinery from closing and these hooks are powered with pneumatics. The machine must be driven to retract so the hooks don’t have any pressure on them and then air moves the hooks out of the way and the machinery can then close.

Even better is to dump any accumulator pressure and block the flow.