laser + pwm in sync with motion, how?

as per the title, using a Mesa 7i76E, is it possible to have a pwm signal output in sync with motion?

normally this is done for a laser or to control a laser


in the interest of full disclosure, I am playing around with the amperage control on a plasma cutter. nothing fancy I just need a pwm signal in sync with motion

I think a common way to do this is with M67

M67 will work, M3 S60 won't as the spindle speed is not in sync with the motion (i.e. motion will slow down when the "S" is issued.

I'll give M67 a shot and see what happens (I didn't realise that LinuxCNC had 3x analog outputs which are in sync with motion).

The plan is to start at "full" or default current setting and then ramp the current down with the M67 miscellaneous code. The M67 must be issued before the next motion command.... so M67 before M3 won't work, but M67 off = 45A will work

The default starting currents will be adjustable, just done before the cutting starts automatically for 3 or possibly 4 settings (45A, 40A, 30A and 20A (for marking / dimpling).

Nothing of these will work correct.
You need mesa datapainter firmware module (see hostmot2 sources).
I asked before a year the same but no ready solution exist yet
for raster laser engraving with mesa.

vre wrote:

Nothing of these will work correct.
You need mesa datapainter firmware module (see hostmot2 sources).
I asked before a year the same but no ready solution exist yet
for raster laser engraving with mesa.

I don't think Robert is looking for datapainting but it would be good if PCW could give us an update on this from the Mesa side and also if you could give a reference to the hostmot2. source. I looked here but did not see anything on first glance but know Mesa was working on datapainting. github.com/LinuxCNC/linuxcnc/tree/master...rivers/mesa-hostmot2

Robert, you could also look at a custom component. It might use M67 to set starting behaviour (does not have to be just a PWM, might be a current handling profile number). The component could monitor the motion.motion−enabled pin (which will see a change of state on M3 and M5 and taper the current off over a time period or turn it off on an ArcOK or whatever algorithm you want to invent.

And you can add more analog pins if required by changing your ini file settings.

Actually I think M67 will work for this since the plasma current setting is not a high
bandwidth data stream synced with position (like a laser) but rather a stepped
current setting that can be likely be synced with gcode.

PCW wrote:

Actually I think M67 will work for this since the plasma current setting is not a high
bandwidth data stream synced with position (like a laser) but rather a stepped
current setting that can be likely be synced with gcode.

Yes I think that M67 will work just fine as it will only be changing occasionally (think of it like a feedrate setting) any ramp required will be dealt with by external hardware.

Thanks for all your input