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  • Building another laser cutter

    A friend gave me a nice coherent Gem-50L co2 laser and so I could build a laser cutter. It’s a pretty nice laser, rated 50W and doing 62. Datasheet here: http://www.istcgroup.com/pdf/GEM_50L.pdf

    I have decided to make it as an attachment for the mill which will attach to the dovetail on the ram.

    First thing I need to do is get the laser under control. I need to be able to run it at low power to check the orientation of the ATFR mirror that stops back reflections from the work. It needs to go in a certain position relative to the orientation of the polarization. Of the output beam. If it’s 90 degrees off it will absorb 97% of the beam instead of reflecting it.

    To control the laser I am building a small box that handles the enable, mode, and PWM signals that the laser needs to work. For this I reused a little Teensy 3.1 board and pcb I made to attach to the back of a vacuum fluorescent display. I made another daughter board to attach to it that handle the IO. I really should have just designed a new board and send it out to JLCPCB with amount of time I reworked and debugged finding and fixing he mistakes I made when I laid out the Pcb years ago. I still might to clean it up. It’s a mess.

    You may only view thumbnails in this gallery. This gallery has 4 photos.

  • #2
    this'll be a great build to watch, following with interest! What will that power laser cut? Paper, wood, acrylic and..? Will you be able to use it for etching alu or steel with the appropriate coatings?

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    • #3
      Following!

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      • #4
        Originally posted by mattthemuppet View Post
        this'll be a great build to watch, following with interest! What will that power laser cut? Paper, wood, acrylic and..? Will you be able to use it for etching alu or steel with the appropriate coatings?
        -Generally speaking, a CO2 laser doesn't have the right wavelength to directly etch metals. You can mark those metals with a marking compound that the laser basically burnishes into the surface, but not actually etch them.

        CO2 lasers are mainly used to cut thin wood, or engrave thicker pieces, cut or engrave acrylic, etc. I think it was somebody here that used one to cut a gasket out of raw stock.

        Doc.
        Doc's Machine. (Probably not what you expect.)

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        • #5
          acrylic, wood, the usual suspects. Also latex sheeting. I make outfits and costumes from latex for shoots with friends. This will allow me to make much more detailed appliqués.

          Nah. You can mark metal with co2 if you have enough energy. There is a guy that uses a similar model with 100w and was able to mark and cut steel with it. Generally you need a much better setup to do that though with beam expanders and “cut quality enhancers” which I plan on adding to the laser.

          im currently sitting in the hospital with diverticulitis so my plans are killed for this weekend.

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          • #6
            I got the optics mounted as well. They are attached to an aluminum stud which mounts inside the mirror block. Machine a fixture out of scrap plastic to get everything aligned. After that I coated the optics with a special polymer optic cleaner that is also good for storing optics.

            there are two normal foot plates silicon mirrors, one phase retarder and one ATFR. The ATFR and the phase retarder are what make up the cut cut enhancer. The ATFR reflects in s-polarization and absorbs the 90degree off p-polarization. The beam is reflected
            off this and hits the phase retarder which converts lineat
            polarized light into circularly polarized light. When this hits something reflective when cutting the beam bounces back and is converted from circular to p-pol which gets absorbed by the ATFR.
            You may only view thumbnails in this gallery. This gallery has 2 photos.

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            • #7
              Since the ATFR absorbs energy I made a special mommy to hold it.

              You may only view thumbnails in this gallery. This gallery has 3 photos.

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              • #8
                What’s the deal with these fibre lasers? I don’t think I understand them (like quantum mechanics really) anyhow, I look forward to seeing your always impeccable work,
                mark

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                • #9
                  Originally posted by Doc Nickel View Post

                  -Generally speaking, a CO2 laser doesn't have the right wavelength to directly etch metals. You can mark those metals with a marking compound that the laser basically burnishes into the surface, but not actually etch them.

                  CO2 lasers are mainly used to cut thin wood, or engrave thicker pieces, cut or engrave acrylic, etc. I think it was somebody here that used one to cut a gasket out of raw stock.

                  Doc.
                  That was me. It least I can say that I’ve used a laser to cut gaskets. Works great.

                  Sid

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                  • #10
                    Originally posted by boslab View Post
                    What’s the deal with these fibre lasers? I don’t think I understand them (like quantum mechanics really) anyhow, I look forward to seeing your always impeccable work,
                    mark
                    There are basically three kind of laser with fibers.

                    Fiber coupled laser - where they take a generic laser, could be solid state, semiconductor, or gas and use a lens to focus it in the end of a fiber. These tend to be used for applications where you need a whole lot of light and don’t care about beam quality because it really sucks. A major application of these is for diode pumped solid state lasers where the diode or a series of diodes pumps crystals in the head instead of using something like a flash lamp or arc lamp. Way more efficient this way since you can tune to laser to the absorption peak.

                    Next if fiber lasers. These are like diode pumped lasers and fiber coupled lasers combined. Instead of dumping light into a clear quartz fiber the fiber itself is the amplification medium. Add a q-switch and you can have some nice high peak power which is great for cutting metals.

                    The new kid on the block is Direct diode lasers. These are similar to the fiber coupled lasers but with the advances in diodes and optics they can get a much cleaner beam out and beams over 2kw. These seem posed to take over a lot from the fiber lasers for applications where you don’t need the high peak power of a q-switched laser.


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                    • #11
                      Thanks very much, made sense, what doesn’t is why all the fibre laser cutting machines seem to be Chinese, I have a mate who has a shop, his workhorse is trumph ( or somthing like it but typing that letter combo will get a firm beating and gchq opening a surveyalance file on you, lol), he reckoned USA is the origin but the guy loading the steel said probably from them Chinese, they have lasers cutting up everything, I thought funny myself
                      mark

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                      • #12
                        Trumpf. One of the most advanced laser builders in Germany.

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                        • #13
                          Originally posted by boslab View Post
                          Thanks very much, made sense, what doesn’t is why all the fibre laser cutting machines seem to be Chinese, I have a mate who has a shop, his workhorse is trumph ( or somthing like it but typing that letter combo will get a firm beating and gchq opening a surveyalance file on you, lol), he reckoned USA is the origin but the guy loading the steel said probably from them Chinese, they have lasers cutting up everything, I thought funny myself
                          mark
                          uhh, I'm not familiar with any Chinese fiber laser, or any industrial sized (kilowatts for cutting metal) laser of Chinese origin. Only ever seen the garbage-tastic <= 100W units, usually 25 or 50W. Epilog knockoffs with shoddy tubes.

                          Trumph is German, Amada and Mitsubishi are Japanese (however Amada has a big facility in southern California). I can't recall the name, but my local favorite sheet metal shop for quick turn laser stuff has an RMD (?) that was made in Turkey. (it wasn't RMD, can't recall what it was, definitely made in Turkey, they had one of the first units in the US and the company even goes back to their shop to demonstrate it occasionally, for which they got a healthy discount on the price)

                          Never seen a Chinese fiber laser yet, although I wasn't really looking for one specifically. I am a machine tool brand aficionado, so I would notice one, though.
                          Last edited by psomero; 02-10-2021, 12:24 PM.
                          -paul

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                          • #14
                            Fiber laser are pretty easy to make. That’s why you are seeing them coming out of China. Are they reliable? Ehhh. Not nearly as much as a fiber laser made anywhere else.

                            The epilog knockoffs are co2s, not fiber laser.

                            Here’s a fiber laser system from China. https://m.alibaba.com/product/170000...pg_200x200.jpg

                            There are a lot of cheap fiber laser markers coming out of China. Galvo based and you can get the whole system cheaper than just a fiber laser from IPG.

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                            • #15
                              Heck yeah! Love it.

                              The

                              " I need to be able to run it at low power to check the orientation of the ATFR mirror that stops back reflections from the work."

                              seems to be a big consideration before all the other stuff. Dont want to cook the tube too soon you need it

                              Neat! JR

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