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qplasmac is a complicated GUI. Normally, it is set up assuming a mesa card using pncconf. 
I think I  would try running up pncconf and build a rough config for a 7i96s. You just need a template for all of the plasma specific pins so pick a mesa pin to use for each. don't worry about scaling the axes etc
Then I would copy the pin layout to your hal file and make sure any plasma  specific stuff in the ini file is copied to your ini file, then replace the Mesa pins with your lcec pins. 

With linuxcnc running open another window and type halcmcd show pin lcec should list all your Ethercat pins and you could probably filter out just the inputs or outputs

Also reviewing recent plasmac configs on the forum may help
I have one but its a very complex one with lots of custom stuff so would not recommend following it github.com/rodw-au/showstopper/tree/master 

In the qtplasmac GUI, there is a couple of fields for THCAD parameters. Set the offset to 0 and scale to 1 and use the actual torch volts. You may need to use mult2 to calculate the full scale voltage. Alternatively, use the scaling field which might be better.

Good luck
 

tommylight wrote:

Yes you should leave them out, as noted above the only usable way for DMM drives is in Position mode as they have a delay in position signal outputs.
Also the encoder input will be used for THCAD if you want plasma.

By "leave them out" I meant to not connect them at all. But then how the linuxcnc will know where it is at certain point ? I will probably loose a part of precision with not connecting the encoders feedback.

tommylight wrote:

Yes there is, Mesa 7i85 or 7i85S should have 4 encoder inputs.

I see this card has a DB25 connector to connect it to the computer I suppose, or does it gets connected to the
7i96s ? Sorry for dumb questions.
Is the DMM Dyn4 encoder output supported by the Mesa 7i85 ?

tommylight wrote:

No, not per se, but LinuxCNC can be programmed as you need it, so a simple G04 P1800 will make the machine wait for 30 minutes at the first cut to preheat the material.
Same for outputs and solenoids, everything can be automated and even add a side panel with settings and buttons and stuff.

OK for this, I will take a look better on it once I install it in a virtual machine.

saxa wrote:

I see the board has only one input for the encoder feedback. But I have 3 drives, so should I leave the encoders
signals from the drive to linuxcnc out ?

Yes you should leave them out, as noted above the only usable way for DMM drives is in Position mode as they have a delay in position signal outputs.
Also the encoder input will be used for THCAD if you want plasma.

saxa wrote:

Or there is a way to connect all 3 encoders to the board ?

Yes there is, Mesa 7i85 or 7i85S should have 4 encoder inputs.

saxa wrote:

Also has LinuxCNC some settings to make the preheat , and open the various gasses vales at ceartain time already in or should I be doing this from zero up ?

No, not per se, but LinuxCNC can be programmed as you need it, so a simple G04 P1800 will make the machine wait for 30 minutes at the first cut to preheat the material.
Same for outputs and solenoids, everything can be automated and even add a side panel with settings and buttons and stuff.

In an Ethercat world, I think you can use a Beckhoff 0-10 volt analog interface as it has similar over voltage specs as the THCAD. People have cracked the Hypertherm Ethercat machines here. But do use industrial Ethercat cables in a HF world

I recently bought an old plasma + oxyfuel machine to retrofit and resell. I awaits me first finishing some other projects. I plan to connect ethercat servos directly to a linuxcnc pc. I have not yet studied the serial interface for the big XPR plasma power unit that came with it. On a previous project I used mesa + THCAD, never heard any complaints from that one.

Welcome. Have a look in the ethercat section. There are a couple of stickies. There is a seperate Ethercat master application that runs on the Linuxcnc  PC and there is another driver that connects Linuxcnc to the Ethercat master which in turn talks to all your slaves. You should be able to use a Beckhoff analog input (0-10 volts) to read the divided torch voltage. Other than that, it will be similar to what Tommy described for Mesa hardware. The Beckhoff modules are rated for over voltage of 500 volts, same as the Mesa THCAD. I'm uncertain that other brands of analog inputs have this protection. I can't help with oxy.

During cutting or at idle?
-
If during cutting, check grounding, if it is shallow under ground, the ground getting dry will cause that.
If at idle, there are a lot of things that can cause that, like other machines in the shop, changing the power socket, stepping on the wiring, wiring isolation failing somewhere due to fatigue and/or strain, and if in Europe, even your neighbor installing a new air condition unit, etc etc.
A simple solution to remedy the latter, use a 0.01 to 0.022 uF (also known as 100-220nF) capacitor on the THCAD input.
I use a 0.1uF electrolytic one rated for 50V but that might lower the reading speed, although for me it works perfectly fast till 6m/m, i have not tested it faster.

Hey when i first built my table my thc would read only + or - 1-2 volts over time its gotten worse and worse now it reads + or - 8 volts or so. Any idea whats causing this? Its running off raw arc voltage with a bunch of resistors in series. 

saxa wrote:

Now recently I have visited some exhibition and I saw today most of industrial things are on EtherCAT.

Yes, it does seem so...

saxa wrote:

My plan is to make linuxcnc act as an master node, and send signals to the motion controller which will then through some adapters transform the signal to pulse/dir and send to the drives.

That would be redundant as LinuxCNC is the motion controller.
In short:
-buy a Mesa 7i96S and a THCAD
-a used Entrprise PC
-A network cable
-Wire, install LinuxCNC, start wiring drives and motors
-those drives will have to be set in position mode, hence 7i96S
-yeah, wiring, you will need very good quality shielded cables for everything as cables that long will collect a lot of interference, not very important for oxy cutting, but a mist for plasma cutting.
-....well, that is it.

Most people on this forum in your position have ditched CommandCNC and moved to QTplasmac with a Mesa THCAD to measure torch voltage and let Linuxcnc manage the THC function internally.

I still have machines running LinuxCNC (named EMC2 back then) on Ubuntu 8.04, and 10.04 and...
It is all dependent on how you look at things, but i would definitely not discard parallel port as it is extremely reliable, extremely cheap be it as a old PC for 20-50$ or add on card for 10-15$, does not need a BOB (although it is recommended for new users as it adds a bit of safety for wiring).
Overall, when you realize you can have a fully functioning and very reliable machine control for under 50$,that will control whatever contraption you can think of by adding some cheap drives and motors found on old photocopiers, the possibilities rise sky high.
So no, parallel port and 32bit are not obsolete, nor will they be any time soon, they are the perfect setup form learning CNC on a very low budget.
Go out, scavenge some motors and belts and linear rods, build something, then build something else even better, then...
-
Personally i use Mesa cards for everything and by now i have installed over 70 or 80 or 100 (probably more but i have no clue of the exact number), but still sometimes i build machines using a parallel port, even plasma machines that produce huge amounts of interference and THCAD wired directly to parallel port with no BOB, using HF start plasma sources work perfectly but do require very strict wiring and shielding and grounding.
Visit the "show your stuff" section, find topics started by me, plenty of pictures and videos of machines i have built and/or retrofitted, and some other stuff...

I wanted to share my experience from the last several days in case it helps someone else planning a Mesa Ethernet / QtPlasmaC plasma retrofit.

This is not a complaint about LinuxCNC, far from it. After working through the issues, I am still happy to be moving forward with LinuxCNC and QtPlasmaC because I think the plasma feature set is excellent. But I do think my experience shows that the “PC side” deserves more attention than I initially gave it.

My setup:

- Home-built plasma table conversion from MASSO to LinuxCNC / QtPlasmaC
- Mesa 7I76EU
- THCAD2 planned
- Ethernet Mesa connection
- QtPlasmaC
- Separate camera-assisted project running alongside LinuxCNC during some tests

One of my reasons for moving away from a closed standalone controller was that I wanted to experiment with a camera-assisted tracing/scanning workflow, somewhat similar in concept to SheetCam’s Scanything. I have been working on a small project I call FabScan, which uses a USB camera mounted to the machine to help trace parts/templates and eventually export geometry. That type of experimentation is much easier on an open PC/LinuxCNC system than it would be on a closed standalone controller such as MASSO.

I originally planned to use a small MeLe mini PC that I already had. It booted fine, LinuxCNC installed, QtPlasmaC launched, Mesa connected, and the machine homed and jogged. At first glance it seemed usable.

The problem was intermittent realtime/Mesa communication errors. I saw errors such as:

- Unexpected realtime delay
- hm2 error finishing read
- Watchdog has bit
- Smart Serial communication error / timeout
- Smart Serial Port 0 stopped

The PC had a Realtek RTL8111/8168 Ethernet controller using the r8169 driver. I tried the usual tuning steps:

- Dedicated Mesa Ethernet interface
- Static IP, no gateway, no DNS on the Mesa NIC
- Disabled Ethernet offloads
- Disabled EEE
- Disabled coalescing
- Disabled Wi-Fi during testing
- Disabled power-management options in Linux
- Increased servo period from 1 ms up to 3 ms and later 4 ms
- Switched from r8169 to r8168-dkms

The r8168 driver helped a lot. The system would run longer, but it still eventually produced realtime delay / watchdog / Smart Serial failures. In my case, the MeLe was simply not boring enough to trust as a control PC.

I also found a separate issue that was not the PC’s fault. My generated config had PID loops driving Mesa velocity-mode stepgens, with DEADBAND = 0.0 on the joints. After homing or jogging, the axes would twitch slightly because the PID loop was chasing sub-step position error. Adding deadband fixed that:

X/Y/Y2:
DEADBAND = 0.0008

Z:
DEADBAND = 0.00025

That stopped the axis twitching.

Eventually I replaced the MeLe with a used Dell OptiPlex 7060 Micro with Intel Ethernet. With the Dell, I tested QtPlasmaC, FabScan/camera load, and NoMachine remote desktop while watching Smart Serial. The Dell stayed clean at a 2 ms servo period. Smart Serial stayed at:

fault-count = 0
port_state = 3
run = TRUE

For over an hour, the takeaway for me:

LinuxCNC can run on modest hardware, but for Mesa Ethernet I would not say “any old PC” is good enough without testing. I would now strongly prefer:

- Used business-class Dell/Lenovo/HP mini PC
- Intel wired Ethernet
- Good BIOS power-management controls
- Dedicated Mesa NIC
- Long latency tests, not just short ones
- Real workload testing: QtPlasmaC, camera, remote desktop, Wi-Fi if used, etc.

I am not posting this to criticize LinuxCNC, again, far from it. QtPlasmaC is exactly why I am doing this conversion. I just think new users coming from MASSO, Mach, GRBL, etc. would benefit from clearer up-front guidance that the control PC needs to be “boring,” not just powerful enough.

In my experience, horsepower was not the issue so much as the details. The NIC, driver, BIOS/power-management behavior, and long-duration realtime stability mattered a lot. I wish I had understood those details better up front, so I am posting this in case it helps the next person avoid a few days of chasing intermittent gremlins.

stoobydale wrote:

Wow that just got expensive. This is a portable table, the cut dimensions are adjustable at the design stage and I am probably going to make mine 1000x800. The designer suggested a Nema 23 stepper kit with DM542 drivers and a Mach 3 controller from Aliexpress at about $235. I was hoping to use something like this probably with just a different break out board. Is this not possible? This is for hobby use and I am in QLD Australia if that makes any difference. This is also my first build, hopefully learn something and able to modify or make a MK2 at some stage.

I'm also  in Queensland also (Brisbane). You can find my email address on my @MrRodW YouTube channel. You can use a parallel port breakout board.I bought 2 off Amazon for $20. I might have a THCAD which you can use with the encoder component to read torch voltage for THC. If you went with Mach3, you'd probably need to get a Proma THC or similar so it will get expensive quick too. The DM542's should be fine. Very hard to kill. Geckos are way overrated.

For plasma and starting with LinuxCNC with stepper motors, I would get a Mesa 7i96s and a Mesa THCAD2 to read the torch voltage. Also get a Meanwell MDR-60-24 24 volt power supply for field power and a Meanwell MDR-10-5 5 volt power supply for logic. When you order your Mesa gear also get some of their DIN rail mounts and a couple of COMMX2 bus bars. That will set you up for a running start.

Hi everyone,
I'm currently building my plasma CNC setup with LinuxCNC and need some help with wiring. Maybe someone here has the same plasma cutter.
Hardware:
- Plasma cutter: Stahlwerk CUT 60 P Digital
- Motion control: Mesa 7i96S
- Voltage sensing: THCAD-2

My main question:

I'm trying to understand where to find the ARC starting signal on my plasma cutter. The signal that tells LinuxCNC: "The arc is burning, movement can begin."

In many tutorials or forums, I read about a dedicated ARC OK output on the plasma.
(See Attachment: the plasma cutter signal control has 4 pins 1, 2, 3 and 4)

On the Stahlwerk CUT 60 P Digital, I only find:
1. THC interface
2. The control socket (where the hand torch trigger normally plugs in) (pin 3 and 4)
3. I can´t find pins 1 and 2 or find anything to how to get the arc signal otherwise 

My specific questions:

1. Does the 2-pin THC output not only provide the voltage for the THCAD-2 but also a signal that tells me whether the arc is stable?

2. Do I need to get ARC OK somewhere else? I read in another forum that some plasma units don't have a dedicated ARC OK and you have to use a current sensor (e.g., Hall sensor) to detect whether current is flowing. Could this be the case with Stahlwerk?

3. What about the control socket? When I unplug the hand torch from the control socket, I have the contacts that previously connected the trigger. Does the Stahlwerk send any signal back through this socket that I could use as ARC starting signal? Or is it really just a passive input for the trigger?

4. Generally what should I do?

What I already understand:

- The THCAD-2 connects to the THC interface (the 2 pins) and then to the encoder input of the Mesa 7i96S. That's for THC voltage measurement.
- Torch start/stop ill get it directly of the cable
- But what about ARC starting signal output? How does LinuxCNC know the arc is actually there and can safely start moving?

How would you solve this with the Stahlwerk CUT 60 P Digital?** Is there a hidden ARC OK output I'm missing? Or are you all working with a current sensor?

Any help is appreciated – photos or pinouts would be great if anyone has them!

Thanks in advance