Hello all,

I've been using Mach for mills and lathes for about 7 years.  Now I'm trying to get a rudimentary plasma table functional, but can't seem to get Mach to light off the torch.

My relays function properly and will turn on the torch when inputs are given, but I'm not getting the signal to the relays. 

Going to Ports and Pins, Spindle Setup, Output 1 is selected for M3 and M4 and the "disable spindle relays" box is unchecked.

On output signals, Output 1 is enabled, port 1 is selected, and Pin 16 is entered.  I started with pin 10, but changed to pin 16 after doing some reading here.  I have verified the common is good using pin 18 for the +5v ground.  The positive lead is going to the solid state relay.  this relay functions and the torch fires when given both the +5V and ground.

This tells me I'm not getting the signal from the computer to the relay. 

Here some more info.

On motor outputs spindle is not enabled.

Back to spindle Setup tab, I'm not really sure what to do with the motor control field of this tab.



On motor output spindle is not enabled.

What BOB are you using?

First of all in most configurations of a single parallel port pins 10-13 & 15 are input pins only so that wouldnt make the relay operate.

So pin 16 is connected to the relay, which is an output.

I would put a check in the disable spindle relays box. I say that because my lathe has it checked and it works fine and on that lathe I have no directional control. I do have speed control though. Just on or off.

On this same set up the motor output is enabled and oddly only the step pin (1 in this case of port 2, USB SS). Step Low and DIR low are both checked (green)

Again on this same set up under "motor control" in spindle options, use spindle motor output is checked, step/dir motor is checked, PWM base frequency is 5 and % is 0. It works on my spindle. Worth a try to fire the torch.

the motor control is being handled by a Hobbycnc EZ board.  It is functioning properly, the XYZ stepper motors are working properly.  The Hobbycnc board does not have outputs other than for the XYZ motors, so I have added a "CNC signal control center" in line ahead of the Hobbycnc board.  The "CNC signal control center" is from Brent Hubbard. 

The control center allows for the parallel port signals to be either passed through to the HobbyCNC board or diverted to a separate set of screw terminals for inputs and outputs.   I'm currently using PIN 16 as my spindle output pin and pin 18 as my -5VDC connection.

According to Brent, "the 5vdc negative must go to ground to give a return path for the signal.   On the negative terminal of the solid state relay (SSR) you will apply a +5volt signal from your control pin from the computer and when you want the torch to turn on, you will drop that pin to 0 volts and the +5 volts of the power supply will turn it on. This will only happen if the negative of the 5vdc power supply is connected to the computer ground.

Am I wrong assuming in assuming pin 18 qualifies as a computer ground?

Assuming my choice of pins is correct, and knowing that if I apply 5VDC to the solid state relay the torch fires, it seems safe to assume that the relay is not getting the signal from the computer to fire.

This statement "when you want the torch to turn on, you will drop that pin to 0 volts and the +5 volts of the power supply will turn it on" leads me to believe the Mach settings should be low active.  Is that correct?

Anyone have a basic xml file for a plasma machine using relays.

I probably should have mentioned that I have a Proma THC connected using the HobbyCNC boards input pins.  It comes to life when the HobbyCNC board is turned on.  Could this somehow be affecting the ability of Mach to turn on the torch?

If anyone ever finds this thread looking for the same problem I experienced, the problem getting the torch on/off relay appeared to be a complication of trying to use the Proma THC.  Without the proma THC inputs enabled, the relay works just fine and the torch turns on and off just like it is supposed to. 

I'm quite frustrated with the Proma THC and the lack of guidance for setting Mach 3 to use this device.   Time to do some more Proma research and possible start a new thread. 

I'm experiencing the exact same problem right now as you describe. I know of someone else who has gotten it to work, I think it's all in the mach program itself but what to check and uncheck I don't know.

The Proma setup is about as easy as it can be, you need to have the torch wired to the proma and displaying proper torch volts when working, do this first by triggering the torch manually. Then get the proma talking to mach3 - this needs three mach3 inputs, up, down, arc ok.

Make sure you have a fully licensed version of Mach3 or it will not work. Then get the proma into test mode - this outputs sequential up and down signals, the z axis must respond to these but to get this you might need to check the setup option of "allow thc inputs when not in thc mode" in ports and pins plasma settings.

once that is working, turn that option off or it will ignore the arc-ok signal.

IIRC that is all thats needed, BTW proma are or were very good on email support, broken english but good still.

The torch on/off relay is not connected to the proma and again this must be verified working before trying to use the proma, the torch must fire when you press the spindle on button on screen or issue an M3/M4 command and go off with an M5 command.

i had a ohhhhh ok moment lastnight and got it working but don't quite understand about main voltage setting on proma box can you explain?? i was told the higher or lower the voltage is set on mach is what determines the height of the tip of the torch as it cuts above the steel.

no, you are using the proma - Mach has no knowledge of your voltage etc - ALL height control is done via the Proma, mach simply controls the motion in XYZ, nothing more.

you set the voltage on the proma but before you do that you need to know what voltage you desire.

this means test cuts - straight cuts about 150 - 200 mm long, set the height manually as per torch manufacturer specs using feeler gauges etc and then set mach to cut at the speed recommended or the speed you deem it will cut properly.

now you need to make a test cut and watch the voltage on the proma - it will jump about a bit but should settle long enough to get an average reading, say its 150v for example.

when the cut finishes, dial in 150v on the proma, connect the up/down signals etc so the proma is talking to mach, then when you make the next cut, the proma should try its hardest to move the torch height to maintain the set voltage +/- a small dead-band which i think is adjustable.

that is basically it, but DON'T FORGET, the voltage you have just set is ONLY correct for that thickness metal AND at that speed - change either one and you need to get a new voltage by the same methods, soon you will have a list of voltages, thicknesses and speeds and can simply dial in what ever metal you are cutting.

There are more complex THCs and these DO have the voltages on the mach screen etc but i think the cheapest one is going to be up in the £700-900 range

Thanks for explaining that to me, the factory settings I assume leave them all alone then?? well i have messed with them but i put them back to factory settings as the manual says.
I know i have seen some high dollar THC out there and figured i'd get the proma because so many people were talking about it. Proma guys in the email were very confusing but i have had help from a guy here in the USA who has helped me a lot in getting it going.

Thanks for explaining it more clearly.

Chris