[dck]

Hello,
I wonder how I can do to make the plasma cutting machine stop when the plasma arc is lost.

How can I do to monitor a input in the mach3 and when the plasma arc is lost while cutting the machine stops immediately.

Note I can't use the THC On input.

[tommylight]

Why can you not use the ARCOK? no THC??
You can still have the ARCOK signal without a THC, but it requires a bit of knowledge and a bit of experimenting.
It is risky in that it can fry your BOB or computer.
You need a piece of thin isolated wire wound around the clamp wire from plasma, make 3 rounds and at one end you need to attach a diode and a resistor, all in series with the wound wire, AND another zener diode for 5V connected parallel to that setup, on the BOB or PARAPORT side.
Do a bit of testing and up the windings till you get a reliable signal. Use a 1K resistor.
Tom

[dck]

Why can you not use the ARCOK? no THC??
You can still have the ARCOK signal without a THC, but it requires a bit of knowledge and a bit of experimenting.
It is risky in that it can fry your BOB or computer.
You need a piece of thin isolated wire wound around the clamp wire from plasma, make 3 rounds and at one end you need to attach a diode and a resistor, all in series with the wound wire, AND another zener diode for 5V connected parallel to that setup, on the BOB or PARAPORT side.
Do a bit of testing and up the windings till you get a reliable signal. Use a 1K resistor.
Tom

I am conducting a retrofit on this machine and I'm installing the THC PHC Hypertherm Sersor, already tried enable ARCOK but it didn't work.
To wait for the signal source plasma transferred arc using the SystemWaitFor (18) in the macro M3.

But is there any other way to monitor this entry?

[tommylight]

I am not sure about how mach controls that but i think it is DWELL or something similar.
In Linuxcnc i have it set so it waits for "motion spindle at speed" signal and use that as ARCOK signal. It normally waits from a signal from the VFD that the spindle has reached the programmed speed and it is ok to start cutting.
It works perfectly and can also be configured for how long will it wait if it uses that signal before it stops the machine. I have it set at 0.2 sec on all machines (7 of them that i own, have built and sold, installed THC etc.), and it is a huge advantage in the saving material department. One of the plasma cutters i maintain and service has an old Oerlicon plasma cutter that generates a lot of heat and the thermal protection kicks in often, so all i have to do after it cools down is go 1 line of gcode up and select "run from here". No unusable parts !!! also we have power cuts often ( sometimes several times a day ).
So, try to find how mach waits for spindle at speed signal and use that.
Tom.

[vmax549]

The ARCok signal is generated by the plasma cutter . It is simply a relay that closes when the arc is established. There will be 2 leads coming from this relay. Route the leads to your BOB(breakout board) to use a spare set of inputs. Set up the ARCok input in Mach3 to match the port and pin setting for the input you used.

With that set up Mach3 will NOT start motion until the ARCok signal tells it the arc is good AND will stop motion IF the ARCok signal is lost.

(;-) TP