Elite Foreman Gen 1 with Masso - Another Grounding Post

[mscott555 (Mike Scott)]

I have read numerous posts regarding grounding / earthing of the CNC. I have some questions based on those posts I have read.

I have a 220V PwnCNC water cooled 80mm spindle and VFD. I have clipped a multimeter negative probe to the ground pin on the 220V plug coming off the VFD (which would be plugged into a dedicated 220V outlet). If I then touch the positive probe the the spindle I have continuity with less than 2 ohms. If I touch the positive probe to the Y and B rails, or the X rail I get between 6 and 10 ohms depending on what I probe. That resistance is not low enough from what I have read.

I am considering running some tinned copper braid from my spindle to my dust collection hose to groung the dust hose running to my dust boot.

I also want to install a grounding bus bar under my wooden CNC base/table to then run grounds to the CNC frame and/or the CNC control box and dust collector motor. The bus bar would then run to the ground which is plugged into a ground only dedicated 110V outlet. I should note that I have clipped my multimeter negative probe to the CNC control box 110V ground terminal on the plug. When probing with the positive probe i have no continuity to the Y, B or X rails.

Now my questions…

I understand STAR grounding which is why I want to install the ground bus bar. However, my spindle (and my dust collection hose if I ground to spindle) are grounded thru the VFD and 220V outlet. If I then ground the machine rails, the CNC control box and dust collector motor through a ground bus bar that then runs to a dedicated 110V outlet ground am I not creating a ground loop? How do I resolve this?

Also, regarding grounding to the rails, where on the machine specifically are you guys and gals connecting your ground wiring?

I’d appreciate your thoughts…

[OnefinityCNC (Onefinity CNC Official ✅)]

Redline Controller Grounding FAQ

Proper Grounding for Redline Motion Control systems. PDF Instructions below (must be logged in to download) PUBLISHED GROUNDING INSTRUCTIONS 2.pdf (7.5 MB)

[mscott555 (Mike Scott)]

This link does not address the grounding issues between 110V and 220V, or once figured out where to ground the rails, etc.

It does answer how to specifically ground the dust collection hose to the spindle.

Any thoughts out there around my questions?

Thanks!

[JimHatch]

@mscott555

This link does not address the grounding issues between 110V and 220V, or once figured out where to ground the rails, etc.

Grounding questions are not their strong suit. They recommend things and then later un-recommend something. And most everything starts with “you’re not grounded correctly”

I have the unmodified HMI (the one without proper internal grounding that the have subsequently added to current production models) and followed the instructions for grounding. Except if they still tell you to ground the HMI to the rail, don’t do that - they subsequently reversed that.

I have grounded the dust collection hose to the machine via a pigtail from the wire in the hose to one of the screws on the back foot. I am using a plug connector because my table flips & is mobile so the hose is not always connected.

I have a ground between the spindle mount & the SuckIt adapter with copper tape lining the SuckIt hose adapter & a wire between that and the spindle mount. Also a wire from the clamp on the smaller dust collection hose to the spindle mount.

I have ferrite cores attached to all the wires attached to the HMI and the VFD & controller as well.

Everything else relies on the grounded power cords and house wiring.

Here are some photos.