Why star ground????

[Kitwn]

I'll side with Muzzer on this one. As far as EMC is concerned, thar be dragons,

Thar be dragons indeed! One of the problems with protecting against electrical interference is that you're dealing with a wide spectrum of frequencies in different circumstances from mains frequency hum to very fast spikes and surious oscillations with frequency components into the mulit-megahertz. There is no single catch-all solution that is best for all ocassions. Only grounding screens at one end is an example. This advice originates from analogue audio and video practice where ground loops lead to mains hum which is both audible and visible even at low amplitude. But as Muzzer pointed out, grounding at both ends has worked for him in situations involving VFD installations where an important aim is to keep fast pulses out of digital circuits.

[Doddy]

Only grounding screens at one end is an example. This advice originates from analogue audio and video practice where ground loops lead to mains hum which is both audible and visible even at low amplitude. But as Muzzer pointed out, grounding at both ends has worked for him in situations involving VFD installations where an important aim is to keep fast pulses out of digital circuits.

In seriousness - I've read and tend to agree with the general philosophy - ground both ends on an emissive line (steppers, spindle) - you really don't care with those and it helps avoid these becoming antennas of high speed, high current signalling whenever the shielding ends/fails. And use star-connected single-ended for susceptible lines (limit switches, estops, etc) where you are trying to avoid any nasties getting INTO the line. I consider it a rule of thumb that's likely subject to any amount of abuse, but it generally works for me. YMMV.