According to the principle, when starting the machine, turn on the filament first. After high pressure. Turn off the high voltage first, then the filament. However, this kind of on-off program has been found in power frequency machines in the past. Now the high-frequency machine is controlled by microcomputer program, and the switch has been set, so there is no need to think about it artificially. You can turn the switch on or off. It doesn't matter.