Properly Grounding Control Panel
Hobbiest here with just enough electrical knowledge/experience to get my self in trouble.
I'm DIYing a cnc plasma machine. I just picked up a big metal NEMA enclosure for my electronics and it came with a galvonized steel mounting plate. I poked around with a multimeter and noticed that there is no continuity between the box and the mounting plate. A thin rubber washer and layer of paint separate the enclosure from the mounting plate's hardware.
My question: do I need to ground the mounting plate on the enclosures grounding post?
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Re: Properly Grounding Control Panel
Yes your mounting panel should be earth grounded, normally the star point ground termination is mounted on this panel.
I have never yet seen a panel that is isolated from the enclosure.
Check out NFPA79 there is a copy in PDF out there on the web.
Al.
CNC, Mechatronics Integration and Custom Machine Design
“Logic will get you from A to B. Imagination will take you everywhere.”
Albert E.
I'll ground it then. The box actually has a couple grounding posts pre-installed for convenience. I thought it was strange that the manufacturer intentionally isolated the plate from the box so that's why I thought I better ask someone who knows what their doing. Maybe isolating the plate is appropriate in some situations, just not a high emi environment like around a plasma?Originally Posted by Al_The_Man
Thank you for your help!
Re: Properly Grounding Control Panel
They may have your cabinet Isolated because you are using a Plasma Machine, the Machine will be Grounded through the Plasma machine, this keeps the noise from interfering with the electronics
You could add a Ground to the star Point, but if you have any electronics not doing what it should then remove it
Last edited by mactec54; 08-02-2020 at 07:48 PM.
Mactec54
Re: Properly Grounding Control Panel
I'm building my own control panel from scratch. This is just a generic enclosure I've purchased from fleabay.
Can you elaborate on what you mean by "the machine will be grounded through the plasma machine"?
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Re: Properly Grounding Control Panel
The plasma machines I have worked on have the Arc positive side (machine table), connected/bonded to earth GND including the service GND.
There was one large manufacturer that used a PC based system using a Galil Motion card in the PC slot.
And of course, a PC has a earth grounded supply on the DC side.
Al.
CNC, Mechatronics Integration and Custom Machine Design
“Logic will get you from A to B. Imagination will take you everywhere.”
Albert E.
Re: Properly Grounding Control Panel
It occurs to me that maybe the rubber washers that are effectively electrically isolating the mounting plate from the enclosure are intended for simply keeping out water.
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Re: Properly Grounding Control Panel
Plasma machines can be problematic with noise seeing you are building it yourself then mount it like it is, Isolated and make sure it is with a plastic bushing around the bolts as well, then add a Ground to the machine frame that you can remove if you have to if the noise affects the electronics, the Plasma machine has it's own Ground, unless you plan on wiring that direct into the cabinet, which may not be a great idea unless you are an expert on how to control the High Frequency noise form the plasma
Mactec54
Re: Properly Grounding Control Panel
All the enclosures I have purchased, Hammond etc, come with a bonding strap from back plane to cabinet also, as well as the cabinet mounting studs.
It sounds like you picked up an enclosure that was intended for some unique purpose?
Al.
CNC, Mechatronics Integration and Custom Machine Design
“Logic will get you from A to B. Imagination will take you everywhere.”
Albert E.
Re: Properly Grounding Control Panel
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