So I am attempting a half solution for plasma cutting. It’s not as ideal as a torch height controller, but better than a one time z home.
I wired my z endstop through the plasma cutter tip, with the ground connected to my z wire shielding. So that it homes to the workpiece. I then took the signal side of the stop and ran it through a normally closed relay. (The thought being that their could be voltage coming from the top back to the control board)
My thought being that in my plasma gcode in estlcam, I can do something like:
G28 Z ;touch zero to workpiece
Gxx? ;Raise the torch up to Pierce height
G42 Pxx S0 ; activate the z stop relay to break the signal connection from the torch tip
G42 Pxx S0 ; activate normally open relay to trigger torch
G04 P2000 ;pause for a 2 second Pierce
Gxx; lower torch down to cut height and continue program.
Then at the end of the cut I would do:
G42 Pxx S255 ; shut of torch
G42 Pxx S255; reconnect zstop
In theory am I going about this the right way? I will adjust the Pierce height/time based on material thickness. This was the first thing that came to mind when coming up with an easy way to adapt to workpiece warpage.
Sounds like it should work. Is the endstop relay a double throw? I think disconnecting the ground and the endstop is a good idea. Let’s hope it doesn’t ever fail to disconnect.
Swing and a miss. It works during my dry runs, but once I get everything buttoned up and all the grounds connected, it results in a false trigger during Z homing. Sometimes the Z will come down to the workplace and touch once, then never do the second slow touchdown. Other times the z axis just goes up each time you try to home.
I went ahead and activated the torch from the greater height, but as soon as the arc touched the workpiece it restarted the archim.
I only broke one side of the Z stop loop, and I definitely should have broken both sides. (I could wire up an additional relay module to take care of that. But I don’t think that would solve the false triggers of the Z.
You can try to diagnose the false triggers with M119. Are you putting a particular end on the gnd vs the signal? The tip is probably at the same ground when it isn’t cutting. Can you do something like put another tip on that is insulated from the cutter?
Something like:
Lift Z
Pause and ask for the probe to be installed
Home
Raise
Pause and ask for the probe to be removed
Kill endstop relay(s)
Go to pierce height
Start torch
Go to cutting height
…
Profit
Hopefully the jump in ground didn’t hurt the archim.
As for a swapable tip, what I was trying to accomplish was automated re homing to adapt to the workpiece as it bowed. Having to swap tips between each cut wouldn’t be useful.
So I did some quick testing with my touchplate harness. It, just like the auto homing worked great…until the various additional grounds were hooked up. The moment you touch the alligator clip to the torch, it triggers. And if you swap the wires, the end stop triggers when the touch plate is in the grates.
If I just go ahead and stick to a single z homing at the beginning of the program, I could use your insulated tip idea maybe? Or what I was thinking was use the existing tip, but use a phenolic touchplate with aluminum tape on the top connected to the other wire.
Just wanting to see if the machine worked in principal, I manually triggered the z stop close to the workpiece. And ran the file…
Presto! I need to slow the feedrate down a bit, turn up the amperage, get rid of the lead in, and possibly change to climb milling to move in a clockwise direction. (Gotta do some tests to see what the torch likes.)
So at least I have a little motivation to get back out there tomorrow and come up with a z homing solution!
After stopping and looking at the design, I see there is already a micro-switch incorporated!
I modified the carriage to have two collars for more stability, and I created a 29mm collar for the machine torch. Currently printing them out, and waiting on the shafts/bearings to ship.
This should allow me to use my gcode for homing before each cut, and no complicated relays to break the z end-stop circuit.
START CUT
G28 Z ;home Z axis
G92 Z-1.5 ;store new z axis height - negative due to floating Z
G1 Z3.0000 F1200 ;set pierce height
M400 ;waits for all lines to execute before proceeding
M42 P70 S0 ;activate torch control
G04 P2000 ;delay for pierce
G01 Z-1.5000 F1200 ; set cut height
M400 ;waits for all lines to execute before proceeding
END CUT
M400 ;waits for all lines to execute before proceeding
M42 P70 S255 ; turn off torch
M400 ;waits for all lines to execute before proceeding
G01 Z10.0000 F2400 ;Lift torch
