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The THCAD-10 and THCAD-5 have been replaced by the THCAD2
 

thanks
I am using the THCAD-10 so I will switch to the mode 1.  I had manually changed in Hal from mode 2 to 0 now will change to 1.
For clarification when running Pnccof should I select mode 1 at that point.
Not having much experience with LinuxCNC but trying to learn.
I am working with another guy starting to build a Plasma table and may use LinuxCNC. Mesa seems to be out of stock on the THCAD-10. Your answer to me hints a Proma THC could be used.

Hello everyone!

My hobby-interest in TIG-welding has opened up new paths on my fabricators journey. I mainly build exercise machines for my own use and I want to expand on my capabilities by building a CNC plasma table. Taking the long way is my go to in pretty much everything I do. I seem to be unable to just buy a plasma cutter and start cutting. I have some experience in using Fusion 360 and a few uni courses on Python coding (a long time ago). I have been relentlessly studying on my off time about plasma cutting in general, and about electrical motors for around three months.

This forum was a fantastic discovery, along with associated youtube channels. And ofcourse, I'm here to learn and ask for help before I buy the components.

MESAs mothercard and THCADs are what I want to go with and due to shortage on the EU-market I cannot pick up exactly the same parts as lets say Rod's Spaceship build.

I will be converting my laptop for Linux and use LinuxCNC. For features, I want to have voltage and ohmic sensing, as the build is going to be fairly large. (half a sheet) Having axes feedback is not a must, but would be great. The frame will be fabricated from 3 millimeters thick 70x70 steel box section. The gantry itself I might choose something like 2 millimeters thick 100x50 box section. Rack and pinion on all axes except Z-axes will have a ball screw.

The main components:
MESA 7i95T eusurplus.com/index.php?route=product/pr...=59_62&product_id=64
It has encoder feedback on all of the axes and I would like to use either hybrid-type stepper motor or servo motors for all axes.

2x MESA THCAD2 eusurplus.com/index.php?route=product/product&product_id=161 
One for controlling the Z-axes by voltage monitoring and one for ohmic sensing.

If I go with hybrid nema 23 stepper motors, do I need additional stepper drivers, or will the 7i95T be enough?

I would prefer non chinese built power supplies, but to my surprise they are not as easy to get as I would have liked them to be. Am I being too picky?

I have absolutely no idea what kind of wiring I should use in the build. We have 230 V 50 Hz mains in Finland. I was adviced not to get any wire crimpers as most of the wiring is done with screw terminals because of the added resistance from the crimps.

I have hopes of using a Hypertherm plasma cutter, but If my budget wont allow it I will choose Everlasts plasma cutter as I was highly impressed by the neat insides of one of their welders on one of Kevin Carons videos.

Any feedback on my ideas for the build would be greatly appreciated. Hopefully I can document the whole journey well enough to be shared for everyone.

Best regards,
Olli

santy wrote:

Thank you. Could you point to this cable please?

Its simply a modified ethernet cable as described in the Mesa instructions. Tajjke care that you understand the difference in cable wiring standards

Thank you. Could you point to this cable please?

Yes, you can use any sserial interface card directly with a 7I96S
(The 7I96S has one sserial expansion port)

No additional hardware is needed (other than the
connecting cable)

Hello.
I need an analog input card for my current project.
Can i use the 7i87 with a 7i96s? What interface would i require to use both cards simultaneously?
I use regular mini PCs with 1 ethernet port

Thank you.

The formulas are in the thcad manual
Bypass the resistors for the 9 v battery test

tommylight wrote:

Yes, 2 of 1MOhm resistors will do, mount them inside the plasma, then it should be OK to mount THCAD inside the cabinet.

 
What kind of voltage will I see coming out after I use these 1Mohm resistors with a 9v battery connected to it?

The THCADS and the power supply I mentioned are both rated to overvoltage of 500 volts way above your open circuit voltage so you won't kill anything!
The normal cutting range is 130v to 170v or so but check your cut charts.
Voltage will likely go over 300 volts briefly when piercing but that does not matter at all because the THC is not enabled at that time. If you plot the voltage with halscope, it will just show up as a flat line when the thcad hits 10 volts (or a little over)
I'm just going to invent a rule of thumb here and say up to 65 amps, use the 10 volt setting and set full scale at 200 volts (20:1) and above that set it to 300v (30:1)
The goal here is to get better resolution from the analog to digital conversion to use as much of that that full scale when cutting.
I never had any issues with my thermal dynamics 120 amp machine with 30:1 and most of my cutting was at 40 amps (It did not have a lower divider  or I would have tried it.)

Thanks RodW,
I curious about the voltage for arc voltage. If running it through a voltage divider, what is the voltage I am looking to get? I am trying to understand it and the voltage that I think am shooting for is dependent if I have my thcad2 set to 5v or 10v. So if set to 10v I need to set my voltage divider to send out arc 10 volts to the thc? If wrong please correct me and educate me on what's going on here.

Second, to determine the resistors.

Do I base it off the open circuit voltage of 305v? Would I then use a 30:1 divider? or is it based of the rated output voltage of 143 and using a 15:1 voltage divider.(ratios based off of assumption above)

Yes, 2 of 1MOhm resistors will do, mount them inside the plasma, then it should be OK to mount THCAD inside the cabinet.

Hello,
So I have decided to not go with the voltage divider from  Hypertherm and just make my own. I believe I have found where all the wires are located that I will need. Check out pictures below.
 
J32 plug appears to be where I will be getting my arc voltage from
J18 is Arc transfer(arc ok) and Plasma start
 
In this photo is shows which wires are what on the plugs
Starting from the top J18  Red and Black = Start plasma, Green and White = Arc transfer (ArcOk)
J32 Black and Red = Raw Arc Voltage
 So to wire this up, J18 red and black wire them to my Mesa board output + - and the green and white I hook the white to my input and the green wire to power supply. J32 Red wire a resistor(Size unknown) second resistor(size unknown) after the first to the black wire black wire to negative side of THCAD2 and red wire after R1 to positive side of TCHAD

So I have a question for you  tommylight . I have seen you say that all one needs its two resistors 1Mohm rated at 2 watts and connect one to each wire and not a voltage divider. So my question is if I was to do it this way could I still mount my THCAD2 in the control cabinet or would I have to mount it on the plamsa machine? My mind tells me this would still be high voltage but very low current but I haven't done any calculations on this to see how low the current would be since I don't know how much currents these machines pull.

 

I'm sure Sean won't mind, if I share his 7i96s plasma wiring diagram here.   I'm not saying its perfect but I think it covers everything. I would not ground the high voltage side of the THCAD as shown as it adds some AC ripple into the torch voltage.


Spumeco, Now you just need to add one for a mill and lathe 

I would say water. I had to ad da refrigerated air drier and it fixed everything.