Machining Process Time link through signals to the Robot

Hello all,

I am trying to use one robot for 2 machine processes. Both Machine has different process time. I am using the robot to load and unload the part. I want to link all 3 components Robot, Machine 1 & Machine 2 with signals so that once the process is done on the machine, it sends out a signal for unloading the part. I want to use that signal in robot programming to run pick and place routines. The question is What should I use as the machine to communicate with the robot back and forth, which has a delay time for simulating the processing time?

Please let me know if I can explain the requirement further.

Thank you!