Using a isolated ground rod without an additional connection to the building service ground bus is very hazardous to the operator as well as the equipment, even though some machine specifications may call for this. It's also non code compliant for this reason.
......Using the conduit system for a ground is acceptable according to the code, but is not a good practice for CNC machines or sensitive equipment. The conduit system can have electrical noise on it from other equipment, and can be coupled into your CNC controls. It will protect you from short circuit faults and electrocution, but can be noisy and cause logic errors on sensitive equipment.
As the title says. Do you ground your CNC machines or other machines for that matter? Boss man says they do not need to be grounded I disagree. What is your practice? Thanks.