MPCNC Co2 laser help

Hello everyone,

I have for the most part successfully built a Co2 Laser system mounted to my MPCNC. I am running a mini-rambo board which I hope to upgrade to a full rambo in the future for end stops. So I have ran into an issue with get the laser to fire consistently. I programmed the mini-rambo to use the Z-Max as the PWM output to my laser power supply. This does give me a nice solid 0-5VDC depending on what I set the fan output to or by utilizing M106 Sxxx gcode. However my laser does not fire from this signal alone as it needs another signal to tell the laser to fire which my power supply terminal is listed as -L (fire on a low signal). For now I just have the PWM signal jumped to that terminal which does cause the laser fire but it seems poor and inconsistent. This leaves me to believe it needs another signal from my mini-rambo possibly TTL? Is there a way to go about this or does anyone have some suggestions?

I should note that if I manually fire the laser it produces a very solid powerful beam so I do not believe my hardware is faulty… yet…

Not sure how to fix it, but that is both awesome, and frightening at the same time! There’s no way in hell I’d fire that thing with my face in the same plane as the beam.

Yes took a while to get everything aligned. Lots of masking tape to check where it hit and standing far away from the invisible beam of fire. Definitely will be building an enclosure and proper fume extraction in the near future.

edit It did not help running it from SD card instead of the laptop. I’m stuck for now until I figure this out.

Ok so I think I figured out that it runs better if I ground the -L terminal. It seems more consistent now however the laser power drops off almost completely within 10 seconds. At first I though the tube was bad but then I decided to disconnect the PWM signal to the laser power supply and wire in a potentiometer from the 5V+ terminal to the PWM in terminal. The laser fires extremely bright now. This makes me think something is up with my PWM signal such as a frequency mismatch. This power supply has very little info that I can find online so I'm not sure what frequency is recommended for its PWM input. I have a scope I could grab at work but does anyone know what frequency the mini-rambo PWM outputs off hand?

I have not ran gcode directly from my board yet with the laser. Perhaps my laptop or repetier-host are messing with my PWM frequency. I’ll report back shortly.

So I have determined my tube was bad which I deserve for buying chinese. Should have a replacement here in a week. There is a chance the power supply is faulty but I’ll wait for tube to come in before I find out for sure.

Hello David,

How did you mount the head on the Z axis?

I would appreciate any info on that as I am going to put CO2 Laser on my MPCNC , too.



I used this mount:

With the MPCNC universal mount:

I have some lengthy posts and videos on the MPCNC Facebook page also if you are looking for more info. Just search for David Christie.

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