Connecing the plasma torch to the BOB?

Hi guys
I'm rapidly approaching the time my manual handtorch plasma cutter will be fixed the machine.
I'm not much of an electroninics person, mechanical and PCs are my thing.

My question is, in connecting the BOB to the plasma cutter, to switch the torch on and off, do I need a relay (or something else) inbetween or can I link it up directly?
If I do need somehing inbetween, what rating would I need?

Any help advice would be greatly recieved

Cheers

Danny

Danny ,

search the wiki and the forum for THC ( Torch head controller ) with plasma torch you need to keep the head a required distance from the work to keep the arc going , so what you actually have is the head on a seperate short linear slide
this has a limit switch , also you need to monitor the arc voltage this is used to move the z axis up or down slightly
to keep the voltage steady and therefor the arc . their are a few thc controllers and some diy types i believe
also Mesa do a thc pcb that can be added to your plasma to give the isolated voltages etc too Linuxcnc .

take a look and then see how you feel and we can go from there , theirs also a few hal and ini files about
how many pins do you have left to use on your bob ? , you may need to look at using a second lpt port or migrate to something better such as a mesa 5i25 etc .

My question is, in connecting the BOB to the plasma cutter, to switch the torch on and off, do I need a relay (or something else) inbetween or can I link it up directly?

Some plasma cutters have an interface connector which makes turning the torch on and off easy.
However if your's does not take a look at the wiring diagram, a couple I have looked at have a simple normally open switch in the the torch handle to turn the torch on.
You should be able to wire that to a relay instead of the switch.
In which case the simplest solution is to use a break out board that has at least one relay and set that up for the spindle (M3 on M5 off).
You may also be able to use a relay board that can run off your parallel port break out board.

Rick G

Hi All, thanks for your input.

I'm a newbie not only to CNC but to plasma too.
The machine is an "IPL Cut 40" entry level plasma cutter. the torch is a hand held affair with "LT-50" on the side. When I bough the machine, I was sold some replacement tips that were described by the shop as "drag tips."
It seems like the torch needs to be in contact with the work to spark up - but I'm happy to be wrong?

My BOB has a pair of pins labeled "relay" so I guess this is what connect to the relay that opens and closes the torch trigger, or does it mean the board has a relay already and they connect directly to the torch handle switch? .

I found where to connect the relay to the torch, a small pair of wires that spur out of the long torch cabling with a special connector.
After that the the Estop and XYZ stops are used so I've only got left "A-limit" and a 5V (not sure if it is input or output...)

THC? I read about these when I first embarked on this project and concluded my plasma machine could not strike an arc without touching. Are you suggesting I could use one with my basic machine? Will I need different tips?
A THC would certainly be the way to go - If it will work... I'll have a dig around the forum and see what I can find.

Cheers Chaps!

Danny

Might be a good time to post some pictures of the setup, the BOB etc.
Also a link to the manufacture site.

Rick G