Earthing?

[Neale]

I like to understand "why", because that helps me know what and how. Trouble with earthing and screening, though, is that you can still get odd problems because you can't actually see or measure what's happening, particularly with intermittent problems.

Been testing my new machine, checking machine limits. X axis kept tripping around 20mm or so before it reached the limit (proximity) switch, although it wasn't clear which switch had actually tripped. Cables are all screened CY but run in same cable chain - limits in one cable, with motor Y and Z cables, but separated as far as I could by spindle cooling tubes. No other tripping problems, just this one point near the upper end of X travel. However, at this point the unrolling cable chain was next to the cable to X proximity switch (the usual unscreened thin stuff); I re-routed the proximity switch cable and the problem went away. Similarly, my earlier problems with home switch triggering went away when I moved the control box from its test position on floor in front of machine to its installed position bolted to frame with earth connection to star point. Moral of story? Use good earthing practice, screening helps, but be alert for the unexpected just in case.

I'm using 1.0mm CY for my Nema 23/EM806 combination, but buggered if I can work out where to put my braking resistors...