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Thread: 355nm laser cutter is alive!

  1. #1
    Join Date
    Apr 2012
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    Beaverton, OR
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    Default 355nm laser cutter is alive!

    This thing is getting close to being finished. Last night I tackled controlling the laser from mach3. First I tried using the step pulse output to control the laser. I couldnt get a stable enough pulse train out of the computer for the laser to be happy. Next I tried a 555 timer and some optos. Didnt get very good wave shape out of it to make the laser happy. Finally I just used a 555 timer driven by the output signal of the breakout board to drive the laser trigger input directly. That seems to work. Took a little tweaking of the duty cycle and frequency but it looks like it will work for now. I plan on using a uC to handle the frequency generation so mach can control the power but that can wait.

    I made the first cuts with it tonight. I used some 1/16" stainless as the sacrificial material. I used the roadrunner file included with Mach3 as the sample. I did a search and replace that replaced all the z-.1 with M3s and z.2 with M5s to turn the laser on and off. The scaling of the road runner files was set to .1, so the whole thing was about 7/8" wide. It ran all pretty slow due to all the tiny segments in the code.

    Next I need to put the sides on an a bunch of other little things.




    IMG_2603 by macona, on Flickr


    IMG_2608 by macona, on Flickr


    IMG_2609 by macona, on Flickr

  2. #2
    Join Date
    Dec 2007
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    Stockholm, Sweden
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    Default

    Nice work! what kind of power is the laser?
    I'm thinking of using a fibre coupled diode laser on my cnc but I haven't decided on what wavelenght yet. Powerful 808nm are easy to find but the optics might be tricky. What kind of optics do you use?

  3. #3
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    The laser puts out 6 watts average at 10KHz.

    I have some of the laser diodes you mention. I dont think I would mess with them for a laser cutter. For one i think you are going to have a terrible spot from the fiber. Another thing is many materials reflect pretty good at this wavelength. If i were you i would just look at one of the cheap chinese co2 tubes. That's what I bought for this originally. A 40w tube and power supply can be has for about $250 plus shipping.

    I took some pics of the engravings i did last night after i went at them with a scotchbrite deburring wheel to remove all the burnt slag:


    Both engravings by macona, on Flickr


    Detail of small engraving by macona, on Flickr


    Detail of large engraving by macona, on Flickr

  4. #4
    Join Date
    Jun 2009
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    Nebraska
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    Is this a freq sum generated YAG?? 10kHz is rather high.. so assuming that means its not being q-switched, 6W average makes a BIG Yag! Cool project!


  5. #5
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    Apr 2012
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    It is q-switched and intracavity freq sum. This model is designed to run from about 5khz up to ~30khz with a peak output at 10khz.

    It's the predecessor to these:

    http://www.jdsu.com/en-us/Lasers/Pro...-q-series.aspx

  6. #6
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    Jul 2005
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    Tampa Florida
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    Good job; very impressive laser cutter. Now what? Phil
    Phil Bergeron( AKA 142laser)

  7. #7
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    May 2009
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    UCSB
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    Looking great! I am just putting the finishing touches on my motion platform (currently populated with a 25w synrad head, but a quick lens swap would let it run with 1064nm and with a fresh set of mirrors 355nm), it is really satisfying watching it run.

    Any plans for what you want to do with the beast? With only 6w you aren't going to be able to cut through many materials (although stencils for PCB fab would be a prime candidate) at any reasonable rate, and marking is going to be slow as heck as well with a machine like that. If I ever come across a 355nm f-theta lens I am going to put my head into my laser marker so I can free up the uuberyag for cutting duty. I have grandiose visions of adding a second beamline on my cutter so there would be both a co2 and a yag head sitting ready to go !warn Sadly, I am leaving the lasers on the west coast when I head to MIT, so I will be lucky if I can even get it running well with the co2 laser for the next few years...

  8. #8
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    Feb 2011
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    New Hampshire
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    It is really nice to see a non-projector laser project. The 355nm wavelength is also a lot of fun with so many CO2 systems out there. Without getting into the subtleties of pulse shape and spot profile which for the large and expensive commercial systems can make a worthwhile difference, how is your focused spot size? If I'm right, you don't scan and so F-thata has no meaning (or value) here. So, with no concern about depth of focus, what about a short focal length focus lens and a really small spot. In any case, what do you think about a high speed jet of He or maybe O2 shrouding the cut zone? Might this reduce splatter or discoloration or even speed the cut? I'm asking, I don't know.

  9. #9
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    It ought to cut thin stuff like shims which are hard to machine on my cnc mill. And marking is always useful.

    The spot size is freeking tiny. I dont have a real way to measure it but it is leaving cuts in aluminum what looks like less than a a thou (inches). Right now I am using a 3" focal length lens which gives me a pretty decent DOF at about 1.25mm. If I shorten that down it will decrease that plus decrease my spot size even further. I do have a plano-concave lens that I can put before it to get a smaller spot as well.

    I still have not finished the final beam delivery section. I have some copper nozzles for the tip and have the machine rigged for assist gas. I have used as many oxygen compatible materials in the system as possible so I can try O2. Gas assist is common on laser cutters. They help keep crud off your lens for one.

    krazer, this guy on ebay has some 355nm mirrors. I have a couple of these, they are turn mirrors for an ESI machine:

    http://www.ebay.com/itm/220903665395...ht_3553wt_1124

    I made some useful things with the laser cutter tonight. Some insulators for a circuit board out of Kapton.

    Found my tuning was not quite stiff enough. I think that's fixed now.


  10. #10
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    Dec 2007
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    Stockholm, Sweden
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    Very nice!
    I have 16W Synrad that is going into my machine but it would be cool to be able to engrave some metal also. I'll hunt ebay for a cheap low power YAG for a while I think!

    Krazer: that uber-YAG looks crazy!

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