DIY CNC Milling Machine From Scratch

**JAZZCNC** · 18-09-2016

You haven't earthed the PC to the control box have you.?

Also do you have Earth on the Frame.? I'm presuming all your Earths go to one Star point.?

**Boyan Silyavski** · 18-09-2016

Nothing can cure a crappy board with poor filtering on the signals / i don't know what that is exactly but i know some boards are good

and have it/ .

I had last week's similar problems, fortunately not with the motor output signals, just probes, switches and PWM output. Neiter filtering of line input, grounding, shielding or whatsoever helped. One of said boards worked well in other machine. All worked fine untill i switched my servos.

But in you case a shielded cable from board to motor drive might help. I have resolved a friends machine similar problem once, changing said cable with a shielded one. Problem solved. In fact his cable was shielded before but wires at end were very large, So i cut them at minimum so all is shielded. Changed cable just to be sure though, as i had a better one at that moment.

Are your cables between this and that shielded?

And by that mean that the shield must be grounded to case

**totts** · 19-09-2016

I've tried to make all my signal wires shielded, there are just over two inches long at either end.

Machine frame is earthed via the spindle from one point and all shields are all going to one point. Pc control cabinet is earthed too.

But my pc has a shielded USB cable which means the pc and the control box is actually earthed together and I have had a few false errors at some point saying it was disconnected.

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**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

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**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!

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**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?

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**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?