CNC Grounding and Bonding Article.

[Al_The_Man]

I found this PDF in my archives, may be insightful to a those need some clarification, also a bit on the author.
Also http://www.automation.siemens.com/do.../emv_r.pdf?p=1
Al.

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[Al_The_Man]

Further to this, I just got my latest (recent for me) copy of Eustace Soares definitive 'Book on Grounding, it was first published in 1966 and not only has become the definitive classic, the bible on grounding philosophies, but has been adopted and endorsed by the NFPA, NEC and the International Electrical Inspectors.
Incidentally I went to my favorite used book site, Abe Books, and got a next to new copy for $1.00!
Al.

[Al_The_Man]

There have been a few post lately showing details of BOB terminations, most use the wrong symbols for power commons.
Al.

[kkannan]

Hi all,

I've been reading this forum for wiring ideas for plasma table and came to this conclusion, mostly influenced by what al_the_man posted in 2005 ? in another thread.

1. Computer MB DC ground is connected to the supply ground, this i've tested with a multimeter.
2. All metal parts, computer casing, motors etc are grounded to supply ground.
3. Plasma table is connected to earth ground, however, all else is bolted to table makes supply ground and earth ground connected.
4. Workpiece clamp (+ terminal) goes to workpiece, but workpiece sits on the metal plasma table which itself is grounded to supply and earth ground, correct ?.
5. So supply ground + earth ground + power supply DC ground (black wire) + workpiece calmp ( + lead of plasma source ) all JOINED together.

Could someone validate this once and for all ?

Thanks in advance.
Kannan

[Al_The_Man]

Well I guess it all depends on who you talk to, The machines I have been involved with conform to the PDF in post #1 fig 3 page v.
I used to service MG systems Plasma controlled by a PC based system.
They were installed with a ground rod at the table, but the system ground and the service ground were all bonded to this rod using welding cable.
Al.

[kkannan]

Thanks for the PDFs, there are arguments in favor of local earth rod and service earth only. But overall, bonding everything together makes sense.

[kkannan]

I came across the following link while searching for earthing ground info.

CNC plasma cutting machine - 600 x 900 mm | BCP0609 - Jinan Bodor CNC machine CO.,LTD.

This is interesting, just see how the return clamp is connected to the edge of the gear box. I remember somebody else raised the question will it fry the balls in the ball bearings.

Any thoughts !!!

[Al_The_Man]

Doesn't look a good Idea at all!
The ideal solution there and often use in turntables is a copper or brass circular track with large brush with high copper content.
Al.

[Migilbride]

Al-

Thanks for the PDF. Good resource. Skimmed some of it but need to give it a closer read. Have been muddling though the whole grounding, bonding, earthing learning curve while working on my diy cnc router table. Have hopefully figured a good portion of it out but still have grounding related twitches in my system that I have yet to figure out. Current "Schematic", such as it is, of my system is attached. Hope these questions are not overload.

Question 1: When I run the system, I can occasionally trigger a limit alarm (these are low voltage, normally open limit switches) by touching the machine frame or a stepper motor. I assume this is because I have yet to ground the machine structure. Do I tie the machine structure / components to -V or to Earth? Have seen your comments about this elsewhere but am leary of the term "ground". Tying to earth is what makes sense to me.

Question 2: The x axis and z axis of my machine are running on delrin wheels. I assume this means I need to implement some method of bridging between these partially isolated elements of my system.

Question 3: I have tied all shielded cable drain wires into -V as well with the assumption that tying to earth would actually allow noise into the system. Again, do I tie into -V or Earth?

Question 4: I have read a good deal about DC power supplies that are not isolated from AC Earth internally. In fact, I see folks on this site disassembling power supplies to hunt down these connections and isolate them. Additionally, I have gotten advice to actually connect -V to AC Neutral. Am confused about what makes sense here. Any definitive answer to that confusion?

[Al_The_Man]

The whole 'taking everything to the earth ground ref' is a question of personal preference, that is if the equipment allows it.
I have tended to take the philosophy of using the earth ground reference where possible.
Although the neutral is at earth ground at some point, you should use the service earth ground as the ground point, this is taken to the star point ground plate.
The earth ground should not intentionally be used as a circuit conductor, however, just a reference point.
The vast majority of SMPS and Linear power supplies come isolated.
As the Siemens PDF points out, the machine frame should be equi-potential bonded to the earth ground point, this is where a lot of noise is introduced when this is omitted.
http://www.cnczone.com/forums/phase_...se_issues.html
I never like the idea of running off of a lap-top, the desk top power supply has a earth ground referenced supply, but the L.T. usually does not.
Al.
.

[Mgilbride]

Thanks again Al. Will implement the frame grounding. Unfortunately, I have nothing but laptops lying around. So think I'll have to stay with that. I made heavy use of a shopbot in grad school that was run with an an MDF infested laptop. A wonder the thing didn't burst into flames. It survived and did the job admirably under incredibly heavy use from the undergrad and grad student body.

[Mgilbride]

I guess I'm gaining a new appreciation for the term bonding. Bolt together aluminum construction leaves me wondering how to properly ground it. Did implement some frame grounding after sanding off the anodized layer and bolting on copper bonding points to three key parts of the frame. However, doubt the long term efficacy of these bonds and at a loss as to how to better bond the whole structure. Maybe some drilled holes, self tapping screws, and a squirt of electrically conductive grease? More research and reading in order...while mulling over the possible folly of an aluminum frame. On the bright side. Machine is performing well and at the moment seems much more stable.

[stitch7577]

Hallo Al

i want to clarify few thinks as i have same noise problem as mentioned here but on hybrid stepper motors which is stepper with encoder + i noticed spindle body is little bit kicking which is probably big part of the problem but i am sure it is wired correctly and now isolated from machine body it is Huanyang similar type. I have all cables shielded and grounded to 0V on DC side and all 0V DC side cables connected together and i am still loosing steps.

basicaly what i conected is 0V (ground from all powrsuplies on DC part of the circuit incluting part of spindle circuit where i am sending signals for turning on spindle and pwm

now: what you suugest is coneting also to the 220V parts where i have brown (life cable) blue(neutral) and green yellow(earth) like this: https://elise.ema.gov.sg/safety/images/cable2.jpg

so your suggestion is connect my 0V from dc part of the system to blue (neutral of the 220V part) and yellow(earth also part of the 220V connection)?

also connecting these cables to the spindle 220V side too?

I dont feel very confortable doing this so i decided to clarify it.

thanks for your advice
Stitch

- - - Updated - - -

Hallo Al

i want to clarify few thinks as i have same noise problem as mentioned here but on hybrid stepper motors which is stepper with encoder + i noticed spindle body is little bit kicking which is probably big part of the problem but i am sure it is wired correctly and now isolated from machine body it is Huanyang similar type. I have all cables shielded and grounded to 0V on DC side and all 0V DC side cables connected together and i am still loosing steps.

basicaly what i conected is 0V (ground from all powrsuplies on DC part of the circuit incluting part of spindle circuit where i am sending signals for turning on spindle and pwm

now: what you suugest is coneting also to the 220V parts where i have brown (life cable) blue(neutral) and green yellow(earth) like this: https://elise.ema.gov.sg/safety/images/cable2.jpg

so your suggestion is connect my 0V from dc part of the system to blue (neutral of the 220V part) and yellow(earth also part of the 220V connection)?

also connecting these cables to the spindle 220V side too?

I dont feel very confortable doing this so i decided to clarify it.

thanks for your advice
Stitch