MPCNC Co2 laser version

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This topic contains 8 replies, has 4 voices, and was last updated by  Barry 3 weeks, 6 days ago.

Viewing 9 posts - 1 through 9 (of 9 total)
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  • #101739

    Andrzej
    Participant

    Hello,

    I am adding CO2 laser to my MPCNC.

    I have mostly used mpcnc with 3W laser diode however it is not OK for me. Too slow and cutting some small pieces took a lot of time.

    I once cut a box sth of the size of A4 paper and it took 4 hours with 3mm plywood.

    So you know why I want CO2 laser 🙂

    I have already in my garage Co2 tube, PSU, and all other stuff needed.

    What I fear most is the connecton to the board. I have MKS base 1.6V board.

    I wanted to reuse fan socket that I used for my laser diode but I read it is not possible.

    In fact fan pins uses 0-12V PWM.

    I need 5V logic signal for PSU. I think David( Actually I found it in Aaryn post, so credit goes to him) who built Co2 mpcnc told that one can use whatever 5V signal from the board and the negative pin from fan socket.

    I checked it and indeed it gives the PWM signal.There is one little problem with it.

    It gives the voltage in the range -5V to 5V instead 0 to 5V.

    I assume the tube will fire only if the Voltage is above 0V, so I will have to use the PWM range from let’s say 130 to 200 ( to be on the safe side).

    1. Do you know why it is -5 to 5 V and not 0v to 5V?
    2. Can I disregard it and just use the PWM range 130-200? (m106,m107 command)
    3. Will it be easier to assign D11 pin in firmware for 0-5V voltage?

    I am not quite familiar with electronics and I need your guidance, please.

    #101765

    Ryan
    Keymaster

    There should be a 5v PWM pin on your board but you need a schematic to know for sure, can’t help you there.

    Using half the pwm range will limit your control to 128 levels instead of 256.

    #101902

    Aaryn
    Participant

    You could also try the trick I am using to get my 12 volt fan pins to work with a 5 volt source from the board.

    Many control boards can do this but maybe not all.

    The idea is the mosfet control chip (aka the pwm) is only connected to the negative fan pin. So you can really use ANY positive pin you want. Just find a 5 volt positive pin on your board. And keep your laser connected to the negative fan pin. It works great on my board.

    Good luck. You can test this with a volt meter/ multi meter.

    Test the voltage from any 5 v positive pin and the negative fan pin. Then set the fan speed to 0 and again to 255.  Voltage should be 0 and 5 volts respectively

    #101938

    Andrzej
    Participant

    Hello,

    Aaryn, this is what I wrote in the first post, I followed your advice found on that forum, however I was puzzled why I got -5v to 5v readings and not 0v to 5V, when setting up fan from 0 to 255.

    I checked it and although it gives -V levels till I have PWM up to 130, the tube fires as I expected.

    I thought it will fire when when readig will be above 0V so this means above 130 PWM.

    It fires even if I put small number like value 20 on fan PWM, which is as I wanted and I am happy with.

    Thanks Aaryn and Ryan.

    #101958

    Aaryn
    Participant

    Hello,

    Aaryn, this is what I wrote in the first post, I followed your advice found on that forum, however I was puzzled why I got -5v to 5v readings and not 0v to 5V, when setting up fan from 0 to 255.

    I checked it and although it gives -V levels till I have PWM up to 130, the tube fires as I expected.

    I thought it will fire when when readig will be above 0V so this means above 130 PWM.

    It fires even if I put small number like value 20 on fan PWM, which is as I wanted and I am happy with.

    Thanks Aaryn and Ryan.

    That’s what I get for reading y0ur post from my phone before.  I totally missed the second half of the post.

    I am glad to hear that it is working regardless.  That makes sense to me though.  Your laser is just looking for  a signal with potential difference.  It could be -5 to 0 or 0 to +5 doesn’t matter.  My only concern with what you have setup right now is that your laser may be firing at full power with the fan setting of 130.  If that is the case then you might want to see if you can plug your positive wire into a ground.  That should give you a -5 to 0 signal.

    I am not a pro at this wiring stuff.  I got my degree in electrical engineering 20 years ago then started a career in programming.  Haven’t had any refreshers since then so this is all from a dusty memory and speculation.

    #103594

    Andrzej
    Participant

    Hello,

    I managed to put all the pieces into a working machine.

    However, I have problems with engraving.

    I have already read info about it in some other thread, however I am not quite sure what is the problem

    What I understood is that the older firmware was OK and the new one is missing some component.

    I just get much worse results when engraving with CO2 than with my good old Chinese laser diode.

    I have noticed also that steppers are pausing to take a breath hehe when I put 3000mm/min and I give a drawing where I have many points like spline.

    I have never noticed it before.

     

    #103716

    Barry
    Participant

    Yea, with a bigger laser you have to move faster to engrave.  If you ever watch a “real” laser engraver running, they’re hard to keep track of when they’re doing those kinds of fill areas.  Our machines aren’t light enough to run at that kind of speed.  At least not with these steppers.

    #103738

    Andrzej
    Participant

    Barry,  I know , but I didn’t mean I go to slow.

    I have completely different problem.  With laser diode the shape was not blurry and was not projecting outside of the perimeter of the shape.

    Here with Co2 there are some strange things happening. I have no idea if it has sth to do with the firmware.

    #103769

    Barry
    Participant

    Oh, I see.  It’s not shutting off fast enough maybe?  I seem to recall something like that when they started putting lasers on the mpcnc, don’t remember the fix though.

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