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46$ for 3 resistors and 2 connectors on a piece of board is to much, but i am OK with it, what i am not OK with it is having such narrow connectors for wiring a plasma source that can do 300V at double digit current numbers!!!
Do not buy that, never ever, the connectors are to damn close on the input side.
Don't get me wrong, it will probably work without issues, but the safety margin is non existent, and i insist on safety always.
With THCAD you just need 2 resistors of 1Mohm resistance, the 2W should do just fine, mount those inside the plasma, from those get the wires outside, bolt a plastic box on the back (do not cover fan), and start cutting.
If you do not want to wait for the resistors, you can find resistors on old electronic, the older the better, even different valued ones can do with a bit of parallel or serial connections.
As for my plasma machines, almost all use belts, rarely rack and pinion, and never ballscrews. Belts are holding perfectly well for over 3 years of daily use, never had to change or tighten those as i got a batch of very good quality ones from POW GE, china, but beware that there are a lot of counterfeit ones claiming to be POW GE.
Here are some of my machines:
forum.linuxcnc.org/show-your-stuff/38547...plasma-build?start=0
and some older ones
forum.linuxcnc.org/plasma-laser/37614-ne...icated-build?start=0
forum.linuxcnc.org/plasma-laser/32494-to...plasma-build?start=0
more info
forum.linuxcnc.org/plasma-laser/38974-di...rything-in-one-place
forum.linuxcnc.org/plasma-laser/35349-cn...fo-and-guide?start=0
There are more but can not find them now...

2 of 1 Mohm resistors should do just fine, one on each leg. 2W type just to be safe.

If you put a 2.4MΩ resistor in each leg it would give you 49:1
 and 1MΩ in each leg giving a 21:1 ratio.
i want to know how many resistor watts do you need.

Use whatever you have and make the machine work, then you can see exactly what you are not satisfied with (if anything) and upgrade as needed.
As for resistors for THC voltage, 2 of 1Mohm resistors should do, one on each THCAD input.
I mount the THCAD on the back of the plasma source in a small plastic box always, keeps interference away from the control box and it is also not interfered by the plasma noise inside.

1. Long axis OK. With Plasma, light and rigid is the go as velocity and accelleration is king. The gantry beam does not need to be expensive. I used 80mm x 40mm  x 4mm aluminium rectangular section.

2. Yes. Usa a THCAD2 with youe 7i96

3. I don't know anything about your plasma but you shoud use a blow back non high frequency start torch

4. 6" is fine

5. proximity sensor is fine. Normally you would have a sliding section the torch was attached to. This would slide up when the torch hits the material and trigger the prox sensor.

So I need some advice here and there are some real brilliant folks here, so if I may be able to pick your brains a bit.

It seems that I have to be about the only person here who does not have a plasma table yet, but that is about to change.  I have a router that I am about to replace that is 1m x 1.5m with a 5'x9' beast.  Usually when i build a new manchine, i desing and cannibalize, but since i will be building on a much larger scale than my existing one, there are absolutely zero parts that will be usable on the new machine.  so the original plan was to make a dedicated 4axis to be used as a lathe of sorts, but my source of plasma cut parts will be moving soon, so i decided to make a plasma table.  the problem is that while i am no stranger to cnc, ive never messed around with plasma, so i am starting an inch above zero here.

so it is a few quesitions, so hopefully john, paul, andy, phil, or rod will chime in and share some ideas and experience.  my design isnt set in stone and i havent started any cutting, so i am still flexible.  the overall design is basically cribbed off my smaller router that i built a while ago with a few mods.  overall a super solid and modular design, 

first, the machine i have is 1000x x 1500y.  idealy i would like the x to be the long axis, but that entails purchasing a new gantry beam.  is there any advantage one way or the other that is a necessity for a plasma besides the usual mass and momentum that i am missing?  my thoughts are that having the longer axis open would make loading and unloading easier, but is it worth the cost of purchasing a new beam?  i am working on a bit of a budget here, so cost is definitely a factor....  on the other hand, having the short axis open would make it easier to do oversized stock, but i dont really think that would be a real necessity for me, but neither did having a plasma either

second, is a thc an absolute necessity?  if so, i was thinking a mesa thcad2.  i absolutely love mesa cards and the machine is running a 7i96 right now.  is that compatible with a thcad2 or do i need a different card?

third, i have a vulcan 45 plasma, but it doesnt have any control ports on it.  putting one in is easy enough, does anyone have any experience with on of these and if so, how did you wire it up?  and how big of a resistor would i need between the vout and the thc?  should i put a fuse in it as well or is it fine with just the resistor?

forth, how about clearance height?  the z axis i have has 6" of lift overall, but im pretty sure thats overkill.  but if i can reuse it, that would be nice.  it really isnt cut out for routing, has more flex than i can tolerat, but i figured it would be ok for a plasma since there is zero contact.  i can modify it if needed, but if not necessary, then why bother.

and finally, i am undecided on how to do the material height sensing.  i was thinking of a spring loaded carriage on the z with a switch or proximity sensor.  i want sure how a proximity sensor would handle that much noise that close and if it would spaz out.  same as an optical sensor unless i found how to shield it.  i really would like to keep it as simple as possible.  touch and done.  

also if there are any other things that i might be missing here feel free to chime in, all advice is welcome!  im going with ballscrews and pretty sure that my speeds wont be enought to worry about whip, so i should be fine there i think. 

thanks for time and input here, much appreciated!

Check out my plasma table build thread.   From this point one we get more into final adjustments to the cutskill.
forum.linuxcnc.org/show-your-stuff/42118...rea?start=150#281696

If you are prepared to do the adjustments (minor at that) then its a pretty reasonable option given it will deliver 60A.   Machine torch is a key addition.  I got a PTM-80 but there are PTM-60's out there.  For some reason more expensive.  And when you get it you need to make sure the pins on the adpator are correctly mapping to the the pins on the cutskill.  The default for these torches is not always what you want.  When I got my PTM-80 torch having it custom wired for the Cutskill was an option. I just needed to spell out what pins I wanted for connected to trigger and consumable installed ok.

Splicing into the Trigger circuit wasn't hard and installing the thcad and a relay into the unit and wiring it up to my own custom CNC port took a little itme to be careful but ultimately wasn't difficult.

Now it looks like it came from factory with a cnc port and the conneciton is all operating with an internal THCAD-10 for reading the voltage.

Cheers - J.

Custom CNC port drilled, soldered and wired up to the thcad and the realy.  Nice and clean on the outside.



 

Have started the process of properly enabling the CIgweld Cutskill 60 for CNC control.  Stage one is a mounting bracket that holds the THCAD and the relay for torch on/off control.   Note that ArcOK is handled via a reed switch on the work return lead.  This has proven to be operating very reliably.

Pic 1 shows the front view the THCAD-10 front and centre.  The mounting is off the aire pressure control.
 

Pic 2 is looking down the length of the bracket. You can see the blue relay on the back side of the bracket.
 

Thanks - J.

 

That worked. Thanks Peter. I will just download and compile as a rule.

Yes, I would download and re-compile
 3.4.0 is about 2 years old

instructions at bottom of page:

github.com/LinuxCNC/mesaflash

Oh ok. Didn't realize that. We should ask the gents to put the latest in master at least.
Do I have to download and compile?

Yes, that's pretty old:

peter@peter-HP-EliteDesk-800-G1-USDT:~/bitfiles$ mesaflash --version
Mesaflash version 3.4.8

My mesaflash is from Master branch. Can it be outdated?
My version is 3.4.0-pre1
 

You may need to update your copy of mesaflash.

I get:

peter@peter-HP-EliteDesk-800-G1-USDT:~/bitfiles$ mesaflash --device 7i96s --addr 10.10.10.10 --write 7i96s_dpl.bin --reload
Checking file... OK
  File type: Efinix bin file
FLASH memory sectors to write: 11, max sectors in area: 16
Erasing FLASH memory sectors starting from 0x100000...
  |EEEEEEEEEEE
Programming FLASH memory sectors starting from 0x100000...
  |WWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWWW
Board configuration updated successfully.
Checking file... OK
  File type: Efinix bin file
Verifying FLASH memory sectors starting from 0x100000...
  |VVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVVV
Board configuration verified successfully.