How I resolved my EMI issues

CNC Machines
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I am in Southern AZ. It’s hot and dry. I have a basic workbench w/ inset router and my CNC cabinet next to it (same level). I have a little Rigid and Dust deputy going to 4 gates.
Lately I’ve been doing a lot of plastics like acrylic and at times had EMI disconnects. This week I started to try my first tray. It was some remnant at the local woodworkers source that was about 1.75” thick. My machine wouldn’t run more than 20 seconds before disconnecting. So I spent a couple hours searching and finding a few different posts. Here is what has worked for me (so far :crossed_fingers:).

I have a wire connected to the closest outlet’s ground using this device. (This is where lights and router are controlled with a light switch.)
https://www.amazon.com/gp/aw/d/B071J61CSV?psc=1&ref=ppx_pop_mob_b_asin_title

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That is connected to the wire in my flexible air hose. Then at my Sweepy I ran aluminum tape and tapped the wire of the air hose to Sweey with some of it tapped on the inside to provide grounding to the router casing.

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Prior to that one, I had connected ground to all three rails at the stepper motors and the ground near the controller.

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I even ordered some kind of USB thing that I was going to connect before the tablet. But I don’t think I need that now.

The only question I have is, will I run the risk of frying my controller having the same chassis ground as the controller & stepper motors as the dust and router case?

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Ground is ground. It is providing a path for stray voltage to be dissipated to Earth. I did the wiring as you showed. I also provided a path to a Buss bar that is grounded to two ground rods on either end of my shop. You know the theory, if a little is OK a lot is better.

Will be building a new shop soon and plan on copper sheets under the slab.

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I would agree with @Zman that ground is ground. In US electrical systems there is a single ground rod driven into the ground usually at the service entrance. So where the 220vac comes in there is a common ground that all circuits connect to. In the electrical service there is a ground bus bar and a neutral bus bar. It is not allowed to attach neutral to ground and ground to neutral. They are kept separate to avoid ground loops. Ground loops can cause small voltages to go round and round in your grounding system. So there is nothing wrong with using a ground from a separate circuit branch because ground is ground and the ground is common on all your electrical branches if the electrician set you up correctly.

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At the main service entrance, the ground bus and neutral bus are connected. Only here, no where else.

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Awesome @Etch8SonsCustoms

IMO For the most part ground is ground however this is AC. and noise can be higher frequency AC

I work with RF equipment and the higher the AC frequency is the less ground is ground. However most times ground is better then no ground. And some time weird crap happens :slight_smile:

Here is a quote on ground loops from the web==>
“According to Faraday’s law of induction any time-varying magnetic flux passing through the loop induces an electromotive force (EMF) in the loop, causing a time varying current to flow. The loop acts like a short circuited single-turn transformer winding; any AC magnetic flux from nearby transformers, electric motors, or just adjacent power wiring, will induce AC currents in the loop by induction”
<==

When we have multiple sources feeding a machine it can be hard to prevent a ground loop, try to avoid them but if not keep them short/small.
In theory AC ground “should” be wired like a star/tree trunk

Some points to note:
The ground of the router can be coupled to the ground of the CNC machine creating a loop. Some people put the router on another circuit, this creates a large ground loop to the panel and back.
Some people ground the wire in the vacuum hose to both sides, this can create a ground loop. I connect it to the Vacuum ground to get it draw it away from the CNC machine.

Most times there is no issue and it may be better then no ground. but depending on what it runs by … Weird stuff :slight_smile:

If you add a choke to the DC power line you might be choking the frames only path to ground. ( curling the power cord up in a loop can create a choke ).
I personally ground the frame of the CNC machine to the the same ground that it is plugged into with a good ground stranded 14AWG. Keeping it short.
IMO I want the easiest path to ground to not go through the controller. so I choke the DC line to keep AC off it and provide a better frame ground straight to the receptacle by passing the controller. Similar to @Etch8SonsCustoms. :+1:

I like to think of controlling the EMI like controlling water,
where do you want the noise to flow, add a good ground path. ( bigger pipe)
where do you not what it to flow. remove the path or choke it. ( cut and cap the pipe, or pinch the pipe to stop or (choke) the flow )

My Router Pi and CNC Controller are all on the same circuit. 20amp
My Vacuum, lights and other items that do not touch the CNC frame ground are on another. 15amp
I have added a new/better frame ground to the receptacle. added a ground from the y rail to the x rail. Choked the shielded data line and the DC power line
Keep the AC lines away from the data lines and DC power cable.

And that what works for me :slight_smile:

Thanks for sharing @Etch8SonsCustoms

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I like the analogy of water. Taught that for a class I had to teach new techs. Water will find the easiest path.

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So will my kids.
Ha ha.

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