DIY CNC Milling Machine From Scratch

**Davek0974** · 19-09-2016

The case of the pc should not be connected directly to the machine, if it is, try removing that link, I have suffered with this.

is the BOB ground connected to the chassis? pretty certain it should not be, none of my boards were.

**totts** · 19-09-2016

No bob ground/neg isn't connected to earth, will remove the earth from the USB cable tonight

Sent from my iPhone using Tapatalk

**totts** · 19-09-2016

So disconnected my USB shield from one end (control end) ran a program only moved 0.3mm instead of the 1.2mm, but found the resistance was high in the earth, the continuity on my multi meter was struggling to pick it up, I checked continuity through my control cabinet earth, which in turn is connected to earth ring main, pc and the USB again, managed to my continuity back, will run a program agin and hopefully will get that 0.3mm back!

Sent from my iPhone using Tapatalk

**Boyan Silyavski** · 19-09-2016

Today i cured all my problems by connecting my VFD ground directly to metal box with electronics inside. Incredible but yes.

As i read that Dean suggested no ground from box to PC, i remembered that when was desperate i did exactly that. Took off ground from PC side and spindle started rising and slowing speed. I said to myself that things are getting worse like that, but as the ground to box was still connected i started touching it around. Touched to ground on socket and was better, touched to PC box- better, then accidentally touched to VFD ground and voila, all was fine. They have common ground at socket, but cable between boxes cured all problems.

**totts** · 19-09-2016

So you have USB shield earthed at box end and the vfd earthed there too? Have you a shielded cable from ur vfd to motor?

Sent from my iPhone using Tapatalk

**Boyan Silyavski** · 19-09-2016

I have all earthed at box body -PC, all Transformers inside, etc. The VFD is outside, just near the box. Yes it has screened cable to the spindle connected both ends. So it's connected to machine. Machine is also connected to box. So all also is grounded together at socket. Go and figure then why problems disappeared when i connected VFD box with big box. In other words- they were grounded at socket and machine prior to the bypass cabling that solved problems.

I could only say that my stupid persistence lead to a result. I was many times at point of taking my big hammer and ...

**nairepooc** · 20-09-2016

All this talk of Grounding and Earthing, is making me even more confussed!
Is Grounding connecting to 0V dc and Earthing to a Star earthing point or am I missing something, or are we mixing up the terms?

**Clive S** · 20-09-2016

Originally Posted by nairepooc

All this talk of Grounding and Earthing, is making me even more confussed!
Is Grounding connecting to 0V dc and Earthing to a Star earthing point or am I missing something, or are we mixing up the terms?

Grounding and Earthing often creates a lot of confusion and to some extent depends how old you are. But you don't connect your DC ground to the Star point which is the point where all the screens connect to and then that is connected to the AC earth. The reason for the Star point is to get rid of earth loops (or ground loops if you are old).

Sometimes you have more than one DC power source and again somtimes you have to connect the various DC power -ve together. Hope this helps a bit.

**Boyan Silyavski** · 20-09-2016

Sorry, my mistake then. In my mother language -ground and earth is the same word, not 2 different. So when i say Ground or Earth, i mean the same. Stick 2m long in the ground that is connected to all grounds in house line electricity, mind not the 0 or phase. If we are talking for DC i say Negative or Common ground. I am not sure that's right, but as English is not my native language ...