Grounding and RFI

I know this topic has been beat to death, but I'm still not exactly certain what to do.

I have a PRSstandard with a 2 HP Spindle (single phase 220V) and a Yaskawa V74x Drive. Whenever I run the spindle, it knocks out the DSL internet and TV (AT&T Uverse) in our home. My wife is very patient with me, but it's starting to really irritate me.

I contacted the Yaskawa service shop in our area (North Carolina), and the engineer was very adamant that I should make sure my grounding was up to snuff. After reading all sorts of posts on related issues on the ShopBot forums
(a) I am really wondering why in the world ShopBot doesn't provide grounding kits and instructions for their machines!?
(b) I am convinced that my machine is not grounded properly
(c) I am still not entirely sure I know how to ground it properly.

Since the parts of the table are all powder coated and nicely insulated from each other and the spindle certainly isn't reliably connected even just through to the X-axis rails, I've read that each of these parts have to be electrically connected before grounding the whole mess to the same earth ground as the control box (which in my house is the neutral bar in the breaker box.)

So, I'm wondering what sort of materials and methods other have used to ground their ShopBot. Don't I really just need to ground the spindle? And if so, what sort of connector and connection should I get and where and how should I fasten it? I'm a tad hesitant to just drill a self tapping screw into the spindle housing. If I need to ground the rest of the components, the same question goes for them. What type of connector? How did you connect it and where? And finally, on the other end, do you just slip the ground wire under the cover of the electrical outlet and connect it to ground there?

The machine has performed amazingly well considering that, on closer analysis, I haven't really grounded it at all.

I'm looking forward to seeing your solutions and I extend my sincere gratitude in advance.

Andy
www.RockingFrog.com

I looked at each sub-assembly as a unit, with the idea of not expecting the rollers-to-rails connection to be a reliable ground. That means I grounded the main table, Y gantry, and Z axis individually, all to the same ground location, which in my case is the electrical conduit nearest to the ShopBot. I know the conduit is well-grounded because I installed it myself, and every junction box has a ground wire screwed to the box which runs back to the main panel.

To attach each ground wire to the machine I used a grinder or a file to remove a little paint and bolted the ground wire onto the bare metal. I also removed one bolt at each connection point (leg to main rail, the corners of the Y gantry, etc.), ground off a little paint, and re-tightened the bolt.

I made sure the dust collector and hose was well-grounded, but did not connect the dust collection hose ground to the SB, only back to the dust collector frame. If any item is grounded to more than one location you can get a "ground loop" which can be as bad or worse than no ground.

Andy...
This may give you a few ideas: http://shopbotwiki.com/index.php?tit...g_your_ShopBot

There is absolutely no way to stop radio interference from the CNC without some kind of cage to block the RF signals.

You need a faraday cage: Cheap Trick

-B

Grounding has little value in keeping signals from radiating OUT from a system, or preventing reception of outside signals that interfere with the digital data our bots use.

Brady is correct, a Faraday cage is needed. Shielding works, because it is a faraday cage wrapped directly around the offensive signals.

As a side note- any component, such as the spindle VFD that creates interference has something very wrong. No surprise the manufacturer points the finger at some other source. They must have a big problem and not interested in fixing it unless it interferes with their sales.

I don't have any elaborate grounding system, and have no problems with generating interference or unreliable operation.

My suggestion, take an old transistor radio, tune it between stations, and hold it up to various cables and control boxes and see which one is causing the most noise on the radio. Find the source. If it is cables, you can enclose them in screen wire, but I suspect the motors or controller boxes. They used to be made of metal, now often plastic.. hence the suspicion.

Good luck-

D

Hi Andy,

The RFI problem is pretty rare and the 2 or 3 cases that I have seen were solved with an RFI filter at the power input. The spindle manuals show these optional filters. If you would like to order one of these filters, give me a call.

In addition to being a botter I'm also a ham radio operator and in the case of rfi interance there are always two sides to every story. The spindle is suspected of being the transmitter but the cable connection is the other side of the story. By law the cable company boxes are supposed to be shielded. Most are not. If your tv, internet etc, is all connected to the cable company you may want to check out their connections as well. If its a little plastic box, try wrapping the box with a little piece of aluminum foil and see if it helps at all. If it does, contact the cable company and explain the problems. If they can't or won't help drop a line to your local FCC and they will get er' done! :) Good luck. Russ

Andy,

I had the same problem where mine would knock out my DSL. After installing the RFI filter as Frank mentions, the problem has ceased.

Around here (probably most places), the phone company shares grounds with the power company.

Scott

All - Thanks for the replies!

Everyone picked up on my mention of RFI and keyed in on that pretty quickly. I probably shouldn't have mentioned it because I really wanted to address the grounding issue (which I'm sure exists regardless of the possibility of RFI.) I also probably should have used the term "line noise" instead of RFI. I believe that's what the "RFI filters" actually address anyway. The RFI goes away as a side effect of reducing the line noise on the powerline. But it's the line noise that (IMHO) kills the DSL. I had already tried a faraday cage around the drive as well as the DSL modem. I even started "shielding" my ceiling with aluminum foil! No space aliens were going to tap into my controlbox fer shore! :o Anyway, none of that helped. But, before I buy the filter(s), I'm going to fix my grounding. It needs to be done and if I'm lucky, it'll take care of my DSL issues too.

I just read Gary's ShopBotWiki page on Grounding and it's exactly the sort of detail I was looking for! THANK YOU! It should be required reading for every ShopBotter. It also made me re-think my theory about reducing line noise by grounding the machine. Perhaps the two are completely unrelated and I'll be buying that filter shortly after all.

Thanks for everyone's input. I'm off to Home Depot to buy a spool of green wire and assorted nuts and bolts.

Andy

Alright, I guess I'm drinking the cool aid. The grounding didn't help at all. Now it's just a matter of figuring out why ShopBot is selling a different RFI Noise Filter (from www.eecontrols.com) than the one Yaskawa specifically makes for the drive. Very odd.