Behavior of M3 command im laser mode(M452)



  • Hi,

    when I put the machine into laser mode by command M452 C"exp.heater6" R255 S1 Q20000 laser works fine processing G-Code files except the issue in my former post. M3 command is only used to enable laser. Sxxx parameter in G1 commands set laser power as expected.

    My issue is behavior in idle sate. "M3 S0.01" command does not to enable laser to adjust focus. That would be very helpful.

    From G-Code documentation it is not completely clear to me if M3 with a S parameter is supported.

    • M3 command documentation refers to M453(CNC mode) only.

    • Description of R parameter in M452 is "Rnnn The value of the S parameter in M3 commands that corresponds to full laser power, default 255". My interpretation : S parameter in M3 is supported.

    • further on in M452 description I find "M3/M5 can be used to enable/disable the laser for moves."

    Is laser power control by M3 Sxxx disabled as a safety feature on a non moving machine?

    My workaround is to make PWM output pin an ordinary I/O pin in laser mode. This way I can adjust focus enabling laser power by M42 command.

    My printer is Cartesian type with Duet ethernet 2 with firmware 3.01-RC8.


  • administrators

    @radiomodell said in Behavior of M3 command im laser mode(M452):

    From G-Code documentation it is not completely clear to me if M3 with a S parameter is supported.

    I have updated the documentation for M3 and M5 to include Laser mode.

    @radiomodell said in Behavior of M3 command im laser mode(M452):

    Is laser power control by M3 Sxxx disabled as a safety feature on a non moving machine?

    It's partly safety, and partly because of the way that M3 interacts with the S parameter on G1 moves. There is one laser power setting stored, which is set when an M3 command is received, and set when a G1 command with an S parameter is received, and cleared if a M5 command is received. This is the laser power that is used during a G1, G2 or G3 command. The laser is automatically turned off when the head is not moving, or while a G0 command is being executed.


  • administrators

    PS - there is already a pending firmware implementation request for a variant of M3 that allows the laser to be turned on when not moving, see https://forum.duet3d.com/topic/13272/m950-and-pin-names/26.



  • Sorry, I missed that thread. Yes, focus adjustment is also the reason for me to fire laser with no movement.

    Thanks a lot for your efforts.

    I will be patient til new variant of M3 command is available.


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