Grounding help, UCCNC, UC300 and connection loss

[JAZZCNC]

Hi Gabi,

Ok well you could have a few issues going on here.?

The Uc300 is USB and some USB cables are better than others regards there shielding and ground. So use a good quality cable and keep it short has possible.
Then you have the VFD which is most likely the cause. The Shield of the Spindle Cable should connect to the VFD ground. Some say Ground both ends of the cable and others just one end, the VFD end. Personally I only ground the VFD end and never have any troubles.

Then you have the fact your control system is spread over several areas meaning your probably not using one Central Star ground point. This leaves you open to introducing ground loops.
The cables in your total system act like huge antena sending or recieving signals so if they are not shielded or there shields not grounded correctly to single point then stray signals will be recieved and wrongly seen then acted upon. Which is why your getting troubles because the VFD is a Bad boy when it comes to making noise and infecting any poorly shielded or grounded cable.

So ideally you want one Earth point that all earths are taken from and shields etc run to. Also run a Earth lead from the machine Frame to this same point.
Make sure you run all High power cables separate from Signal cables, so don't run spindle or power cables next to limit or E-stop or drive signal cables.

Ground issues are always hard if not impossible to track down with certainty in situations like this where spread over several places so My suggestion is to get everything BUT the VFD into one box. Keep the VFD separate away from signal wires.
This will make it much easier to use Star ground setup. It will also allow you to get rid of the extension cables which don't always help matters.

Edit: Here's a quick knock up to show principle of Star ground. Notice only one path back to the Earth pin on Wall socket.!
Also Notice how the DC power supplys Ground drawn has black wire is different to Mains Earth. Very easy to mixup DC Ground with AC earth when they are completely different things. DC Ground finds it's path to Earth thru the DC supply so not be confused with AC earth.
We are only taking about AC Earth here and Signal Shield paths to Earth often mistakenly called Ground.