Strange Problems after Laser installation

Hello there,

i wired up my laser on my MPCNC and there were a few problems i cant solve on my own.

  1. The MPCNC takes very long to start the laserjob and stalls midjob
  2. The size and shape of the job is weird(see attached pictures)

I wired my 3 wire laser on GND and PC9 on my SKR Pro v1.2 and the 12V 3A PSU on the 12V of the laser and GND of the SKR Pro v1.2.

Softwares testet:

Any ideas what could cause the problems?

Best regards

The MPCNC performs normal without the laser attached.

Have you tested youre File on the SD Card and running from the mpcnc itselfs? With my old Notebook the USB Connection failure some Times and the Job aborted. What you can Test ist that you make a Job with estlecam starting the laser manuell and Run the Job, cryptobel phrases and letters in Lightburn were Made when you using a cracked Version from lightburn.

Have you tested Quadrat or Rhombus?

No i didnt tested the file from SD.

But i forgot the biggest problem. I cant turn on the laser permanently, it shuts off after 1 second.
Tried the M3 command or the interface on the LCD.

I will test a sample file from SD next time.

This is a safety feature. Unless the laser is moving marlin will turn off the laser

Which GND did you use?

It sounds like an electrical and/or electrical interference issue to me, we’ll see what some of the others chime in and say as they have more experience with these lasers.

In the meanwhile check that the cables have a good connection

When i remember right the laser control over the LCD we’re wonky, but i coild IT on permanent without moving over the LCD.

If you are using inline commands, you need to put the following at the top of your laser file.

M3 I

This can automatically be inserted by Lightburn.

Are you using the same power supply for the laser and the control board? If so, verify the PS has enough current to support both.

If the one second thing is a safety feature, how should i focus the laser?

I used the GND right next to PC9.

The Problem also occurs if i use M3 S25 or M3 O25 or similar.

M3 I is already added like mentioned in the MPCNC Documentation for lasers.

And i use a different 12V 3A PSU for the Laser.

I should be able to check on the laser tomorrow and rewire it and try other solutions mentioned here.

Thanks for the help.

According to a post on this forum, Marlin has the bug fixed. The next time V1 makes a new release of their maintained Marlin firmware, the fix will be incorporated. The laser will then stay on if triggered from a Marlin-driven menu.

My solution (until the bug is fixed) is to manipulate the pin directly, rather than to use Marlin’s laser/spindle commands. See M42 for directly manipulating pins. Another way to get around the bug is to created a script where the laser is turned on, and then the script moves the spindle very slowly for a period of time, and finally turns the laser off.

Another solution is to edit and recompile the firmware so the laser stays on longer when not moving. This is not the best solution for safety reasons, but the line to manipulate is in configuration_adv.h:

#define LASER_SAFETY_TIMEOUT_MS     1000   // (ms)

I finally got back to the laser today and hooked it up again. It seems that the problem is gone for whatever reason. I changed nothing and it works flawlessly.

Maybe it was some kind of interference although i ruled that out because i rewired it about 3 or 4 times the first time i got the problems.

For the focusing part i used M3 S25 F50 X50 for slow movement and focusing.

Thanks for all the help and support!