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High Frequency shielding for CNC Plasma



Gadget
06-23-2010, 08:46 AM
]Here are the promised photos of how I shielded my CNC electronics from the high frequency of the plasma cutter. The braided shield was purchased online and the wires were threaded through them. Pretty easy to do, just compress the braid like one of the Chinese handcuff devices you played with as a kid (I'll bet you had one) which makes a large enough center hole to thread the wires in then once over the wire just pull it lengthwise to cover the wire.

Dan

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weldingtwopotatoes
06-23-2010, 12:20 PM
Thanks Dan for the detailed photos they will definitely help me with my build. On a side note how are your rails constructed? I can see that it is a piece of galvanized pipe sitting on top of a piece of channel but how is the pipe attached to the channel?

Gadget
06-23-2010, 05:46 PM
For the Y axis there are quarter inch threaded rods going through the main beam into the bottom of the tubing. Each main beam has 1.5" holes running through the beam, the 1/4" threaded rods goe through the beam into the 1.5" hole. There is just enough room to put a nut on the rods and snug them down in the large hole.
For the X axis there is only a tube at the top of the beam so the threaded rod goes in from the bottom of the beam up into the tubing.

Arcamm
12-07-2010, 10:40 AM
Hey Gadget, any chance of getting your photos re-posted? I'm talking with a guy who builds cnc router tables about building one for plasma. He's not familiar with the requirements for plasma cutting and electronics protection. Any info would be helpful.

Gadget
12-07-2010, 12:52 PM
Photos are reloaded

samsberr
12-07-2010, 01:00 PM
Good Post...
Very Informative...
Thanks

Charley Davidson
12-07-2010, 01:54 PM
Seems like a lot of work, Think I will stay away from high frequency plasma cutters for my future CNC table. For using non CNC I'm sure it would be fine.

Gadget
12-07-2010, 02:41 PM
My feeling is it is the arc start and stop that causes the issue with my CNC table. I use pilot arc to start my arc but before shielding if it sputtered or quit cutting for any reason it would lock up the steppers.

Arcamm
12-07-2010, 06:20 PM
So you need the shielding even with a pilot arc torch?

---------- Post added at 08:20 PM ---------- Previous post was at 08:19 PM ----------

Oh! And thanks for reposting the pictures.

KHK
12-07-2010, 10:55 PM
From my experience you do not need to stay away from high frequency. You do need to do the shielding. On my CNC ALL wiring is in shielded cable. ALL the shields are grounded in one point like a spider web, with the ground in the center of the web. The control box holds ALL electronics and is isolated from high frequency via a ground.

Gadget
12-08-2010, 07:03 AM
For CNC plasma cutting I would always shield regardless of the torch start.

Arcamm
12-08-2010, 08:50 AM
Shielded it is! Better to be safe that sorry. Electronics can get expensive.

Herba4
02-07-2011, 03:36 PM
Hey Guys,

Getting ready to build my own CNC Plasma/Router table and I came across this link some time ago that I am going to use so that i don't have to buy another Plasma Cutter since I already own a Forcecut 60............ Enjoy!

http://www.randyray.com/TMC/rf_shielding.htm

Xalky
05-03-2012, 08:41 PM
Man, this is no joke. I tried just firing my torch and my computer locks right up. it fires for a split second and then I have to do a push button reboot on the computer. I guess I'l be shielding and grounding the piss out of my equipment if I ever want this to work..

brucer
05-04-2012, 03:36 AM
Man, this is no joke. I tried just firing my torch and my computer locks right up. it fires for a split second and then I have to do a push button reboot on the computer. I guess I'l be shielding and grounding the piss out of my equipment if I ever want this to work..

what plasma cutter do you have?

Xalky
05-04-2012, 07:00 AM
I have the 256pi multipurpose machine. I must say that nothing has been grounded or shielded yet. I was just doing a dry run torch firing from mach3 to see if my controls are working. The torch fires if only for a split second. :) It's so bad that I can't reboot from the screen. Here's the thing though. I have another PC running right next to it and that one was fine,. The torch and plasma are closer to the pc running mach but not by much. It must be coming thru the control wires.

brucer
05-04-2012, 12:59 PM
could it be a grounding issue?

Xalky
05-04-2012, 02:34 PM
Yeah, it probably is a grounding issue. I think I have bigger issues now though. I think I fried the THC board. This gitting real frustrating. I'm not a happy camper.right now. :cursing

acourtjester
05-05-2012, 02:11 PM
HI Xalky
Not to worry I have a Everlast PM2656 Multi-unit (tig, stick, and plasma). I made some test cuts today cutting metal less then 8 feet from my controller. I have the motor wires in shielded cable grounded at the controller end. Limit switch wires in shielded cable grounded at the controller end. I was having a problem when the plasma shut down so I put a ferrite core on the input power and that stopped. The only problem I had was a limit switch signal was stopping the run mode every so often. I am using magnetic limit switches and will change to micro switches and re-test. I don’t know what cables you are using but it seems shielding will help you out.

Have fun
Tom

Xalky
05-05-2012, 02:26 PM
Yeah I'm in the process of shielding and grounding now. I drove the ground rod in today, I drilled a hole right in the floor of the garage and drove the rod down, thats not an easy task in this rocky Connecticut dirt. My table is about 3ft away from that rod. I'm also gonna ground my plasma machine to a different rod. I think right now my biggest concern is getting my PC station well shielded and grounded, I think I'll run a third rod for that. One of the reasons for all the separate ground rods is just so that I'm not tripping over ground wires all over may garage, but the second reason is better isolation.

acourtjester
05-05-2012, 07:36 PM
HI Xalky
Multiple round rods may not be a great idea. I work for 30 years installing/maintaining CAT and MRI systems. When ever we installed a system only one ground was used most of the time the electricians had to run a separate ground cable all the way back to the main power input.
You could end up with a ground loop problem.

have fun
Tom

Xalky
05-05-2012, 09:36 PM
Here's an e-mail that I sent to Tom over at CandCNC:

Me: Will the High frequency torch start on my machine interfere with the electronics, or is everything shielded sufficiently so that the emf emitted from my torch will not be a factor?

Tom: We have everything isolated (even the Torch volts is isolated back to the DTHC side) but getting the plasma side well grounded (earth ground) AND making sure the PC and control side is on a different AC feed and ground is essential to kill the HF start noise. It is not simple enough to just tie everything to one ground and call it good.

---------- Post added at 11:36 PM ---------- Previous post was at 11:18 PM ----------

I'm basing my install on his recommendation of having seperate grounds between table and controls. I can always go back and change it. I think the problem comes in when you try to daisy chain grounds instead of making "home runs" back to the ground Rod.

acourtjester
05-06-2012, 05:44 PM
HI Xalky
I was not saying to daisy your grounds I used a #10 fine strand cable for each run to the ground rod. I have separate grounds from the table, welder/plasma, and computer/control cabinet. The motor drive cables and the limit switch cable each have shields that were connected to the ground lug in the computer/control cabinet and open on the other end.

Have fun
Tom

Xalky
05-06-2012, 06:51 PM
HI Xalky
I was not saying to daisy your grounds I used a #10 fine strand cable for each run to the ground rod. I have separate grounds from the table, welder/plasma, and computer/control cabinet. The motor drive cables and the limit switch cable each have shields that were connected to the ground lug in the computer/control cabinet and open on the other end.

Have fun
Tom
Thanks Tom. I think I understand now. You don't want to ground your items from 2 or more ends, you want all your grounded items, separately, to terminate at the ground rod. An easy example would be your shielding, you don't want to ground from both ends of the shielding. Some times it's difficult to isolate ground completely in that way. For instance my gantry is grounded to the table via the bearings, it's not the greatest, so my shielding on the motor cables and limits also acts as a ground carrier from the gantry to the table, on my setup. Is this not good. The control box is seperated totally. My computer is grounded to the metal computer cabinet and also grounded separated totally. I also have ferrite chokes installed on all wires entering the control box from the gantry. The chokes are at the control box end. I only have one parallel and one serial cable going into the pc from the control box. Those have chokes where they enter the PC.

I think some of this will have to be determined as I go, obviously.

If my shop was big enough, I'd put the plasma table in a metal shed thats grounded with all controls outside the metal shed, but thats not gonna happen here. No space.

Xalky
05-10-2012, 01:05 PM
What about shielding the torch lead and grounding running a home run to the ground rod? It seems that a lot of the noise might be coming from the torch lead. On my table I'd like to run the torch lead close to the motor and home switch runs since they'd all be coming off a common overhead boom. It seems to me anyway,that trying to capture as much of that HF at the source would be a good idea. Any thoughts?

acourtjester
05-10-2012, 03:06 PM
Xalky
I would not put the torch wiring with your motor wiring. The noise is reduced by distance, you may look into two booms, one located on each end of your table. I donít know if you have seen this or not but if you grind metal and metal dust on the floor. And you have you ground cable for the welder on the floor you will see the metal dust will form a pattern like a magnet that attracts the dust on the floor. If your torch wire was on the floor too you would see it around it too. Having the torch wire close to the motor wiring you will get like a transformer action from the torch to the motor wire when it starts and stops, two spikes for each cutting action.
IMHO
Have fun
Tom

brucer
05-10-2012, 07:16 PM
would metal braided sleeving do any good? seems our cnc mills use this stuff on the runs to the controller cabinets and servos..

Tin Copper Sleeving : BuyHeatShrink.com : EMI/RFI shielding Expandable Sleeving (http://www.buyheatshrink.com/braidedsleeving/metal-braided-sleeving.htm)

its expensive, but maybe you can find it off something salvaged.

Xalky
05-10-2012, 08:45 PM
Here's what I bought : LOT OF (10) 3M ELECTRICAL SHIELDING TAPE TINNED COPPER WIRE BRAID 1" X 100' | eBay (http://www.ebay.com/itm/260968622112?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1497.l2649#ht_500wt_1415) I'm shielding and grounding everything I can think of. I just scored some Scotch 24 tinned copper shielding tape off Ebay 1"x1000'..yes one thousand feet, for $75. I'll be shielding and grounding everything in sight :0. I'm gonna take the advice of not running the torch leads parallel to control wires . I' am gonna shield the entire torch lead back to the plasma cutter and ground it to the ground rod.

---------- Post added at 10:45 PM ---------- Previous post was at 10:43 PM ----------

Some have had success in shielding the torch lead on a HF start torch when nothing else worked. I aint taking any chances. I got shielding for the masses.

miikkessio
02-04-2013, 12:02 AM
Nice shielding you've done there!
Gadget, I'd like to know how and to which part of the torch tip did you connect the ground cable for no contact arc starting. A picture would be awesome!:2thumbs

Gadget
02-04-2013, 06:53 AM
Nice shielding you've done there!
Gadget, I'd like to know how and to which part of the torch tip did you connect the ground cable for no contact arc starting. A picture would be awesome!:2thumbs

Hi and welcome to the forum. We like pictures here so be sure to include some showing your work. Be sure to post a bit about yourself in the introduce yourself section so we can get to know you. Also, keep an eye out for the next contest here. The odds of winning a great new Longevity machine are very good.

I ran a 10 gauge wire between the plasma ground clamp connection and the metal threaded barrel of the torch. The threaded barrel is connected to the tip and the electrode is connected to the other lead so the ground connection acts like putting the torch close to metal and firing it up. I don't have that particular torch now so I cannot take a photo of it.
Dan

undercut
02-05-2013, 12:22 AM
Welcome to the forum, miikkessio.

miikkessio
02-12-2013, 01:57 PM
Thanks,
and Gadget, thanks for clearing things up! I'm going to use similiar ''pilot arc'' technique in my new DIY plasma table.

Actually I am now building that plasma table. I just welded the frame and machined some parts out of aluminium for the x&y belt drive. It is hard to find time for the project though. I promise that as soon as I find some extra time, I'll show up in here too!

Logosweld
04-30-2014, 09:39 AM
]Here are the promised photos of how I shielded my CNC electronics from the high frequency of the plasma cutter. The braided shield was purchased online and the wires were threaded through them. Pretty easy to do, just compress the braid like one of the Chinese handcuff devices you played with as a kid (I'll bet you had one) which makes a large enough center hole to thread the wires in then once over the wire just pull it lengthwise to cover the wire.

Dan

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wow nice pics displaying whole process for cnc plasma

Logosweld
06-26-2014, 10:51 AM
The plasma cutting process itself is capable of almost surgical precision. It is the human hand that guides a manual plasma cutting torch that is responsible for the roughness sometimes seen in plasma cut pieces.Today CNC plasma cutting systems typically use the operator's personal computer to create the shapes to be cut and control the cutting machine. The resulting shapes are smoother than would be possible with a bandsaw, and can include intricate curves, inside cuts, and sharp corners.

cwalker1960
08-18-2014, 09:36 AM
Here's an e-mail that I sent to Tom over at CandCNC:

Me: Will the High frequency torch start on my machine interfere with the electronics, or is everything shielded sufficiently so that the emf emitted from my torch will not be a factor?

Tom: We have everything isolated (even the Torch volts is isolated back to the DTHC side) but getting the plasma side well grounded (earth ground) AND making sure the PC and control side is on a different AC feed and ground is essential to kill the HF start noise. It is not simple enough to just tie everything to one ground and call it good.

---------- Post added at 11:36 PM ---------- Previous post was at 11:18 PM ----------

I'm basing my install on his recommendation of having seperate grounds between table and controls. I can always go back and change it. I think the problem comes in when you try to daisy chain grounds instead of making "home runs" back to the ground Rod.

From someone that just finished a build using a hf Esab machine.. Mine is working ,,mostly.. I never have trouble with missed steps or limit switch falses.. but if the torch fires in mid air for any reason it will lock the computer up . I have done everything I can think of or told to do. shielded wires , grounded table grounded computer.. All in all ,if I hadn't have already had the Esab machine I would go with a non hf machine just to avoid all the trouble. in my opinion,, it's not worth it...

Gadget
08-19-2014, 06:09 AM
Hi cwalker and welcome to the forum. When you get a chance please post a bit about yourself in the introduce yourself section so we can get to know you.
Dan