Controlling a CNC machine from a screen interface can be risky because unintentional screen touches can cause the machine to crash. In the best case, the process is still cumbersome because the operator needs to precisely control the machine position (for example, when using and edge finder to set WCS position. Or in the case of the H-Series, doing the same thing with the touch probe.) Pendant control offers a number of advantages over screen input:
Tactile feedback from the scroll wheel (the operator can FEEL when a command is sent to jog the machine), preventing unwanted movement.
Immediately responsive and always-on - quickly adjust machine movement speed, print temperature, or fan speed without waiting for a computer to connect.
Nimble - can be brought to where it is needed to monitor machine movement. Connected by 1.5m cable to controller.