Laser printer problem /configuration

Hello I ‘ve 2 questions/problems to solve.


I want to use Repetier Firmware to pilot an 3D printer for powder Laser.

I use an MKS base V1.4 (normally fully compatible with an Arduino ATMega 2560 added Ramp 1.4). You can see the link for laser and MKS bellow



About movements, everything it’s OK, it seems there’s no problem.


My problems are the following:


-          To managed powder’s hopper/reserve, I want to use electro magnet (5V) è on which pin can I connect it? What is the command (G code) to control it? (it just work on/off)

-          Laser: I used it on PWM mode (only on/off), I don’t need to adjust power. Actually it’s connect on hotbed pin, but the result is not good because it do not work normally, it seems to flash, it’s not work continuously.

It’s seems to be lag with the top of the MKS and the laser (the LED of card is ever lighted and laser work after, as there’s a delay).


Any Idea? What should I do?


  • M42 can turn any pin on/off.

    Sure laser is made to be controlled by 12/24V bed pin? At least my laser as 12V power plus a TTL signal for on/off. That could also explain the delay. Anyhow you can set a delay on activation of laser (LASER_WARMUP_TIME). That will of course add a delay in motions as it has to stop motion for laser warmup.
  • You say that I need to use ttl?
  • M42 can be used for any pin, but it needs to be declare?
  • the seller say that it can be use with PWM 12V... 
    Which connexion should I use please?
  • M42 can be used for any pin, but it needs to be declare?
  • If I enter G code M104 S255, it's better, but some flash (when it change of way), but it's better
  •  M104 S255 is for fdm setting temperature. For laser please use the laser mode which was made for this. See repetier.ino file around M451

    M42 sets a pin as output on first use, so nothing to declare in firmware configuration. There are some pins marked as sensitive which can not be used.

    With TTL I mean a 5V signal. Don't know your laser system, just tell you mine has 12V power supply and a 5V pin for laser on/off signal which I hooked up as laser pin.
  • OK, thank you,
    I've any modifications:

    I use Laser mode,
    Laser still connect to heat bed PIN,
    Do not use TTL, just on/off by 12V 
    it's ok with G0 and G1, laser stop and start when necessary.

    I've put 1000 ms for laser warmup time.

    But I've still some lake during printing...
    It' seems that when it change of direction, it desn't keep laser active.
    So for example, for a square it miss some part of it.

  • Do you think that if I use TTL, it would be more precise, and laser would be activated faster?
  • Firmware V1 supports no PWM. If the electrons has a 5V input for laser it will trigger faster I guess.

    When laser is on depends on the logic. Normally it is on if E value increases. So for slicer set retraction to 0 and set diameter such that even the smallest move increases E. The exact value is not important.
  • Sorry but What do you call "E"?
  • Sorry but What do you call "E"?
  • My laser is working with electronic card and 2 inputs (PWM 12v and TTL 5v)
  • E is the E parameter in
    G1 X120 Y80 E1
    that is the extrustion of the FDM etxruder. Alternatively you can use M3/M5 to turn laser on. Then it is on for G1 moves and off for G0 moves.
  • Yes is what I use M3/M5
  • If I use a manual gcode with M3/M5 it seems to work perfectly. But I 've change retraction to 0 and extruder at 0,2 but nothing change. The only thing I' ve tried yet is to use 5v pin, but I don't understand where connect it and how use it?
  • I can not follow your code changes. Can you post a simple non working sample and tell where laser is on and off. You say you use M3 and talk about retraction and extrusion. It is either using increasing E values or M3/M5. Been a while I used my laser but I'm quite sure it is that way.
  • Ok
    In fact when I use manual code with M3/M5 it's ok, just like this one:

    G0 X150 Y125
    M3 S200
    G1 X200
    G1 Y175
    G1 X150
    G1 Y125

    But as soon I use auto gcode done by repetier it flash as I sayd before.
    So I've tryed to add that in custom Gcode "after layer change" of slicer:

    G0 Y292 F4000
    G0 Y0 F2500
    G0 Y292 F1000
    M3 S255

    it's better but lase is on during moving between the last line (M3 S255) and the starting point of the printing, but I would like no, I would like it start just when it's in position to print not during this travel.
  • And in this config, I'm still connect on pin bed 12V to pilot on/off
  • I've tried to connect TTL (on D51 on my MKS Base) and PWM on 12V, but in this case, laser is always "on".
  • If you use the gcode from slicer you should not use M3 that confuses the firmware as it then mixes extrusion and M3. I think slicers only use G1 so laser will be always on from this.

  • When I test TTL, I've erased M3 code
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