Spindle/machine grounding

[amowry]

I know there have been a lot of discussions of grounding practices, but I haven’t found a definitive answer to this one:

I recently added a VFD and spindle to my K2CNC, and I think I’m having occasional electrical noise issues. I grounded the spindle housing back to the VFD earth, and my machine frame is also grounded to earth at its control box. Does this cause an undesirable ground loop, or should I not worry about it? It seems that using only one of these ground connections would then rely on current flowing through the bearings on the axes.

While I’m at it, what are the current thoughts on whether to connect only one end or both ends of the spindle cable shield to ground?

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[mactec54]

I know there have been a lot of discussions of grounding practices, but I haven’t found a definitive answer to this one:

I recently added a VFD and spindle to my K2CNC, and I think I’m having occasional electrical noise issues. I grounded the spindle housing back to the VFD earth, and my machine frame is also grounded to earth at its control box. Does this cause an undesirable ground loop, or should I not worry about it? It seems that using only one of these ground connections would then rely on current flowing through the bearings on the axes.

While I’m at it, what are the current thoughts on whether to connect only one end or both ends of the spindle cable shield to ground?

Each moving part would have to have a Ground wire connected to it, to do a correct machine Grounding, just connecting a Ground wire to the machine base is not going to work very well, as for a Ground loop, as long as all the Grounds are connected at the same source ( Star Ground ) then you won't have a Ground loop problem, unless you have created a loop, and supplied a Ground from 2 different sources

There are no current thoughts on shield Grounding

To be EMC compliant, the correct way is to Ground Both Ends, for the Spindle to the VFD Drive cable, the Shield is not working correctly if only one end is connected

Some photos to give you and idea of how to connect a shield correctly

[amowry]

Okay, thanks. So should I connect my VFD ground to my control box ground (where the machine is grounded), or it it enough that they are bith grounded back at the breaker panel? Will connecting the grounds introduce noise from the VFD to the control box?

[mactec54]

Okay, thanks. So should I connect my VFD ground to my control box ground (where the machine is grounded), or it it enough that they are bith grounded back at the breaker panel? Will connecting the grounds introduce noise from the VFD to the control box?

The input Power supply to your Cabinet the Ground is connected to a Ground stud or a Grounding Bar /Bus the VFD Ground would connect to this same Stud or Bar just as any other Grounds are needed for you machine

So VFD Ground Terminal to this Ground Point

Spindle to the VFD Ground Terminal

This is a 3ph example, the same applies for single phase