[ptegler]

As an electronics engineer, the CNC router table build has been fun...no noise at all well shielded wiring everywhere.
I ran into an issue with a shorted E-STOP cable not letting a second in series switch operate correctly.
The second switch I'd put at the other end of the table worked fine, but not the one right in my main control box. (????)
I'd apparently crushed the wire on the second switch and the ground (making it look like it was still closed) was the ground from the table back to the elec box. The table was grounding the wire in between the two E-STOP switches.

Now here's the fun part.....
The only ground the table has back to the control box and back to the power mains, was the added ground wire I'd put in the Chinese spindle! Yes my table was that well wired.... the only ground was through the VFD back to the power mains earth terminal, which of course was wired to my control box chassis.

So... my question...... with everything shielded, even have chokes on my Spindle power cables..... earth grounding the table metalwork directly to the power mains earth like the control cabinet and electrical breakers box, and removing the 'added' spindle ground wire inside the spindle, am I creating a scenario for a major leakage path?... a charge getting built up that might later break down insulation somewhere creating a problem?

The spindle power cable is shielded 4 wire conductor. The 4th wire (added ground connection at the spindle end) asnd the cable sheild are tried to earth ground at the VFD, with that same terminal going back to the breaker box mains ground.

[Al_The_Man]

Details on earthing and bonding.
http://www.automation.siemens.com/do.../emv_r.pdf?p=1
Al.

[ptegler]

um.. :-) thanks but that stuff is all common knowledge to me.

I spent years doing International Safety Compliance Testing for the first ever NRTL Lab in the U.S. (Met Labs in Baltimore)
(the ones that sued the Feds back in the 80's and won... resulted in the break up of Underwritiers.... can't have the only policy agency be the only testing lab.... ( it took UL four years to get certified itself! ...it's why you see so many different logos these days.....)

My Q is one of 'leyden jar' effects .....insulation breakdown with these Chinese Spindles...was wondering if anyone has ever had issues.
Not just stastic build up with dust.... but real 'storage' of energy

...fun fact now that I think about it....
Techniquely speaking... these Chinese VFD's and spindles are illegal to sell (or even advertise for sale) in the city of LA, and the State of MD (no testing certs)


thanks anyway though :-)

[Al_The_Man]

A few here have discovered that the fourth (ground pin) on the H.S. spindle was not actually connected to ground internally.
Just make sure you do not operate the spindle below ~ 6000rpm as burn out can occur.
Al.

[ptegler]

from those previous posts, T'is why I added a ground wire connection inside the spindle at the connector..
I just thought it interesting that when all wired up, my table only saw a ground through that added spindle ground wire in the connector.
Unplugging that feed cable ungrounded the entire table. That's how I found the short in my E-Stop cable from the bolt pinching the wire in the 8020 channel groove.

[FineLineAuto]

from those previous posts, T'is why I added a ground wire connection inside the spindle at the connector..
I just thought it interesting that when all wired up, my table only saw a ground through that added spindle ground wire in the connector.
Unplugging that feed cable ungrounded the entire table. That's how I found the short in my E-Stop cable from the bolt pinching the wire in the 8020 channel groove.

I find the highly interesting too. I wouldn't expect your particular table design to ground itself completely just because it's touching the spindle casing that you have ground. My main worry would be if a wire breaks or moves in such a way that it contacts the table and is now grounded. As you saw with the EStop, it presents a serious safety concern with signal wires.


Nate
Fine Line Automation
www.finelineautomation.com

[Al_The_Man]

The link in post #2 explains the necessity of equi-potential bonding to earth ground of all metallic parts of the machine, not just the motor frames.
Al.