Re: Any pics of cnc control cabinets?
Sounds like I need to stop and get a better understanding of proper grounding. There seems to be some mixed opinions on whether or not to tie earth ground to dc common. I always assumed everything should be grounded to the same ground. Currently my dc components are grounded to the small enclosure I have, as well as the a.c. ground and it hasn't caused any issues, but maybe not the proper way to do it? Just wamt to make sure i have this right before spending time on the new cabinet
Re: Any pics of cnc control cabinets?
Hi, i connect the mains earth to anywhere where it is required/where there is an indicated earth connection. But i do not tie/connect the neg of any SMPSU to earth:)
Re: Any pics of cnc control cabinets?
Quote:
Originally Posted by
QuinnSjoblom
Sounds like I need to stop and get a better understanding of proper grounding.
There are two schools of thought out there, some that say you should never ground any of the DC supply commons, the other is to earth reference all supplies, I have always followed the latter practice, with so far no problems, there was a post here a while ago where a poster was experiencing all kinds of intermittent stoppages of his system where he had followed the isolation method, I suggested that he use the ground all method, where possible, the problem went away, there have been others where it has fixed the problem.
A star ground termination point is also very important.
There used to be a paper on the Siemens site on Equi-potential bonding in enclosure installations, but after they changed their web site, it dissapeared, I may have a copy somewhere.
Al.
Re: Any pics of cnc control cabinets?
STAR grounding: everything to a single solid ground point.
Essential to prevent 'ground loops', which can be really disruptive.
Cheers
Roger
Re: Any pics of cnc control cabinets?
I use star grounding for all DC electronics, then I tie that star ground point to the the incoming mains ground. I do not gain or lose axis Step pulses.
I suspect that workplace safety laws will require full connection to the mains ground in all cases unless the entire machine is double isolated - which would be pretty much impossible for a CNC machine.
Cheers
Roger
Re: Any pics of cnc control cabinets?
Some components require the DC supply to be isolated. Connecting the DC- to ground loses the isolation.
Re: Any pics of cnc control cabinets?
Quote:
Originally Posted by
ger21
Some components require the DC supply to be isolated. Connecting the DC- to ground loses the isolation.
And often component suppliers will stress not to earth ground the common of their equipment, from what I have personally gleaned it is often not because of a technical reason, but to avoid any blame if you do ground it and if something inadvertently goes wrong with the installation you can blame their equipment.
If there is no technical reason otherwise, I have always ignored it and grounded anyway, with no ill results. :cool:
Al.
Re: Any pics of cnc control cabinets?
A little late to the discussion, but I have been running the DC return to earth ground for years, works for me. One instance of where you would not want to do this is in the case of direct rectified line power without an isolation transformer, Anilam built a lot of systems like this. Grounding that would cause a dead short. As Gerry noted there are some other exceptions, but normally it is a good practice IMHO
Re: Any pics of cnc control cabinets?
Also one publication aimed at machine/enclosure wiring is NFPA79, you most likely can find a copy out there in PDF.
I would add that just about anything used in a PC desktop/tower environment is going to be earth grounded simply because it is automatically done in the PC, e.g. P.ports, USB ports. Kmotion etc as well as any card that plugs into a PC slot, Galil, Acroloop, etc. are all connected to the PC ground plane that is earth grounded via the service supply.
Al.