I'm using an AC/DC switching supply (Meanwell PD-45) with the following schematics:

The Frame Ground (FG) is connected to the metal chassis of my device with a screw. The output of the switching supply is used to power a PCB. Therefore, +5V and COM are connected to the PCB. But the ground of the PCB is in itself also connected to the metal chassis via the mounting screws. Therefore, COM and FG are connected. Is this a good practice? Should the PCBs be kept floating with COM only?