Hi,
I would like to create a rule to cut off the torch just before arrival to try to reduce the divots.
I don’t know the code and don’t know how to enter the code.
I love this software, I have been using it for 1 year and I would now like to improve my skills in the details.
I thank you in advance for your response.
Holy Cow! that is a timely good question.
I have just within the past week added such a circuit to my grbl v1.1i plasma controller for exactly the same reason. I have been testing it with much success the past 2 days. I’m still refining the Path Rule that turns off the torch before end of cut, basically refining the distance (leading the MCU and relay(s) reaction time) before end at which the Torch OFF signal is lowered. I’ve been side tracked with unrelated projects for several days, so progress is slow.
None of the following may matter to you if you don’t have a controller that supports this ‘feature’ or behavior, but the concept of signaling Torch OFF while XY remains in continuous motion is the point. I have read that LinuxCNC has this ‘feature’, but I can’t speak to Mach3/4, or CandCNC, or other popular controllers. I suspect those may have the feature also so you’d have to look it up. I don’t know which gcode stmts they each use to control this behavior.
In grbl v1.1f+, this can be done while running in ‘laser mode’ ($32=1). In this mode, when M3 or M4 is used to start the cutting cycle, then S word (normally laser power) can be changed while XY(and/orZ) remain in continuous motion. So for example, a Code Snippet having the following gcode will turn OFF the torch with continuous XY motion.
G91 (relative distance mode)
G1 X0 S0 (logic low on Spindle PWM signal.
(The preceding stmt results in no new motion but it is deemed continuous motion by grbl)
G90 (return to sheetcam's absolute distance mode)
The torch will fire with stmt M3 S1000 G1 F1 (the usual max S) in OnPenDown(). This of course means that you have to drive the torch trigger relay with SPWM signal, not Spindle Enable.
In OnPenUp(), you still want to use M5 to keep the torch off during any subsequent G1,2,or 3 motion before the next OnPenDown().
Full disclousre, I’m running with M4 S960 G1 F1 for other reasons that involve another grbl laser mode behavior of variable S power depending on XYZ accel/decl of programmed speed. But I’m using the same torch OFF Code Snippet as noted above and M5 in OnPenUp(). The variable SPWM duty cycle drives a THC Anti-Dive CIrcuit that I built for my machine. So for this reason, I had to build a circuit to mange the torch relay too, but I don’t believe you will need this using M3 as noted. I’m going to update my THC Anti-Dive circuit schematic with SPWM Torch Trigger circuit soon, and post it in this forum.