Earthing?

[Edward]

After reading these post it's all becoming a little clearer, so many thanks.

A few questions that may be a bit naive, but important for me to understand things better:

-I'm in the process of putting all the elements into an enclosure. From a practical point of view, should I buy a plastic or metal enclosure?

-Regarding the star ground connection, if the "star" point is a bolt making contact with the metal enclosure, to which all the grounds are connected, and the 3 drivers metal base are also touching the metal enclosure, does that affect the efficiency of the star connection in any way?

-Also, my 68V linear PSU (Leadshine) the mains input Ac doesn't have an earth connection point so only the Live and Neutral are used, shouldn't the Earth wire be connected to something? When it finally goes into the enclosure the 240V mains enclosure input socket will be earthed to the star point, so I guess that's all that's needed as far as the drivers PSU?

-On my vertical mill spindle motor, there is a ground wire bolted to the back of the motor. Why do you need this if the motor casing itself is already touching the mill metal body, which presumably is in turn also grounded somewhere. Is there a star arrangement within the mill itself?

I can't think of anything else to ask...wait a minute, I notice in the schematic (Jazz) you have a fuse to the PSU, etc. Is this essential or recommended since the PSU is already connected to a fused mains socket?

Edward