So I’ve read a lot about this issue before getting my table and in the short time I’ve had it assembled (2 days) I’ve cut out a bunch of test stuff and a couple of real items. All with very good success. Today I decided to put water in the table and leak check my welds in the seam. As luck would have it I had a couple of pin holes to fix. Drained the table rewelded a couple of spots and refilled the table.
Loaded a piece of metal and did a dry run all good! Started the camera nad it started up did a pierce and quit. Got the voltage waring and I realized I hadn’t put my work clamp on the work itself. Fixed that reset the program push start… Same thing… I run the THC test and sure enough it fails. I unplug the laptop and run the test again and voila it passes.
So strange, I cut my piece out no problem. Seems strange that the only thing I did was add water to the table and now the laptop has to be unplugged. Has anyone else seen this? Here’s the part!
Check continuity between table and shielding on printer type cord that plugs into your control box. It should be open. Plug in computers power supply and check it again. If you get a reading than thats your ground loop.
I drove a 8’ copper rod into earth and grounded the table. Don’t confuse this with your electrical service ground rod. Any emi will be dissipated into the earth. I have never had one issue even while tig welding right next to the table in operation. Like Cletus says EMI is VOODOO. 805400r0 (1).pdf (236.8 KB)
By the way I lived in Newmarket NH for many years while I built an Air Separation Plant in Kittery Me. The plant with the Lobster on the storage tank is the one.
Thanks for that document! I had checked continuity between the usb and the table and only once did i get continuity. Very strange! I think I ll watch it for a bit and see if it acts up again.
Small world! I m in Dover I’ve seen that tank many times. I used to go to the auction over there on Tuesdays.
Hey where did you ground to the table? I’ve got an 8’ copper rod I put in the ground for powder coating figure I might as well ground the table while I’m at it. You just put it right to a leg?
Hey I’m getting my pro soon and wondering if you could post or send a picture of your bonding setup on yours…. I see how they have it the doc but I’m wondering how you set it up exactly on fhe Langmuir so I have something to go from for cable mgmt
Here you go. All the motors are tied to the buss bar on the back of the table. It is connected to the copper buss near the floor that ties the plasma cutter and table to the earth’s ground. The ss sleeve on the positive work clamp creates a Faraday shield around it. It does not
connect the Langmuir control box to the grounding system. It must be isolated from everything.
This awesome thank you so much…. I appreciate you going out of your way to take so many… and I was thinking I understood that part about the braided shielding sheath/tube, and see I sort of do… but I definitely need to find that stuff then. This kind of bonding regime probably seems extreme to some but I’m sure it’s probably a good CYA.
Yes it has a two prong adapter to isolate the computers and control box from the electrical service ground. Not the earth ground. This prevents ground loops though the electrical panel.
understood. thanks, good to know, again much appreciated. yeah i’m just trying be pretty serious about the bonding and grounding of it all as i have some expensive electronics in addition to the laptop that may or may not be used in the shop concurrently with the new crossfire running on the same electrical service… 3d scanner and possibly a separate cnc eventually. i might need to look at changing the service config too bc i think the house and big shop share the same 100amp… inexplicably it looks like the other 100amps of my 200 service goes to the small 2 car detached. no clue there. that and someone did some BS before i got this place with neutral ground… which i understand is acceptable in certain specific configs but mostly not.
do you use usb isolators? ive seen them used for ground loop stuff… but if you’ve effectively eliminated possibility of ground loops with simpler methods its probably not needed?
Now, If you decide to do this chassis earth ground setup be aware that in theory some of your positive DC voltage (work clamp) will be lost into the earth ground rod. With that being said, I have seen NO difference in the plasma cutter performance. Zero.
I run a Everlast 82i and have cut 3/4 steel without any problems at all. Well, that is my disclaimer. Also,I have had zero problems with EMI even with 300 amp Tig machine welding right next to it.
As for your neutral and ground being connected together. The only place this should be done is at the main service panel being feed from your utility.
Now, this may be a hard fix if the prior owner buried the wrong cable. Will it work, yes. Is it to code no.
yeah thankfully the big shop is grounded properly with a rod, its the small 2 car next to the house thats got the funny wiring. i’m just going through everything beforehand making sure i’m not gonna fry anything and assuming that i might possibly use the small garage/outbuilding as a home for the cnc stuff later on so i can sit in the office in the house right next to it and possibly save on having to subdivide space and do too much ventilation work … just have a designated dirty area i guess. and thats really good to know considering i have a lesser quality tig nearby that i use for stainless … and i can definitely hear the high freq start in my shop radio every time… maybe i keep that on the other end of the shop? you know its one of those amazon $500 combo machines with dc tig stick plasma lotos or something. so i’m sure it makes dirty interference. was thinking of selling it and upgrading so i can do aluminum but can’t quite yet after buying the langmuir. anyway your advice and insight has been highly appreciated… and i’ll get to setting this up and try to report back. in the meantime cheers!
the better quesion i should have asked is how did you get the rs232? plugs on the ends of the stepper wires thru the shielding braid? cut/reattach/solder? if it messes with a warranty or something just pm/email me or something or i’ll deduce it?.. deaglebingo outlook… but again thanks for replying before especially when you already commented on this so much earlier and i just didn’t see it in my searching… so also:
i’m posting another link to this thread too that you already commented on to further cement anyone’s understanding if they find this later… sometimes my search skills catches up later after i understand the concept better. Grounding interference solved!.....I wish
edit: wait a second i’m dumb… looking at pics a second time you didn’t shield the actual stepper motor cables… i need to re-read the hypertherm pdf etc you posted and get my shit together on concepts here.
ok now that i’ve finally gotten over covid and gotten the big shop cleaned up set up and insulated… and finally assembled the table… i’m at the point where my replies originally started. understanding a bit more about the whole thing, just to clarify once and for all… the control box itself shouldn’t be grounded to anything despite the psu of the control box having a ground prong. also i’m extending the cnc pigtail to keep the thc break-out box away from the plasma cutter unit itself because i’ve read that velcroing it to the cutter itself is probably not a good idea. i don’t have any shielded cable but i bought a bunch of that tinned copper braid sleeve, do i connect that shielding sleeve to the same “star” (the bus bar that goes to earth)? i’ve seen someone use a phrase “shield away from the field”? maybe i’m getting that wrong. does it go on one end or the other of the extended thc voltage sensing wires and if i run that wire along with the trigger wires in the same shielding sleeve would that be a problem? also are your braided straps from said bus bar to steppers just connected to the metal case of the steppers with ring terminals like under one of the socket head cap screws? i just wanted to make sure i have this right in my head before i start soldering and crimping stuff… sorry for the ton of rambling questions and thank you in advance.
Thats all correct. Except my VMI box is double sticked to the side of the plasma cutter.
I run an Everlast with a chassis ground lug on it. If yours doesn’t, add one to the outside cover and bring it to the Star buss bar.
