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Thread: Looking for a laser to cut acrylic in a DIY CNC machine.

  1. #1
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    Default Looking for a laser to cut acrylic in a DIY CNC machine.

    Hi Guys

    I am really new to lasers and think I am being a bit ambitious for my first build.

    I am interested in building my own CNC cutting machine and would like to use a laser to cut Perspex and Acrylic sheets up to 6mm thick (White and Clear in color)

    I initially was thiking of using a 455nm 9mm Diode from DTR's Laser Shop but have been cautioned about my laser selection.
    The main concern is the cutting ability of the 455nm laser. Will this laser be able to cut through 6mm Acrylic after 2 passes or will it just burn and melt?
    What would the best laser be for this purpose?

    PS. I am trying to build this machine on a really low budget.

    Any advise would be appreciated.

    Thanks
    Xproximity

  2. #2
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    Hi Xproximity,

    Welcome to PL.

    445nm isn't really the place to look for cutting. It can be used for engraving some materials. There has been a fantastic thread posted on using 445nm diodes to engrave wood on here recently but I cant remember what the tread title was.

    If you want to cut things, CO2 lasers are where it's at. Speaking of things, user name "things" who is on laserpointerforum too, built his own CO2 cutter a while ago.

    Being new to lasers, I wouldn't suggest jumping straight into building a CO2 laser cutter though. The beam is invisible and to cut 3mm acrylic you need approx 40W of power from a CO2 tube. High powered invisible beams, electricity and water could be a dangerous mix to start out with.

    Have a look here. This really is incredibly cheap for what it is. You aren't going to really cut anything for much less than this.
    http://www.ebay.com.au/itm/New-Deskt...item1e7b9e4154

    This is probably the best place to start with cutting. It is a turn key system that is relatively safe. It won't cut 6mm acrylic but if you want that, you will have to spend quiet a bit more money.

    Do some research on CO2 laser cutters. They range from 40 Watts up to 6000 Watts for industrial machine that will cut 1" thick steel.
    If you decided you want something bigger after using one like the one in the link, you can buy all the parts that make one like this and mix and match to suite your required cutting thickness and cutting area.

    If you add your location to your profile you might find someone near by who can help with parts plus it makes things a little more personal.

    Good luck and have fun.

    Kit

  3. #3
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    Hi Kitatit

    Thanks for the quick response

    I am a bit worried with going straight to CO2 lasers as I wouldn't know where to start, not to mention the cost of the laser tubes, mirrors and lenses as well as shipping to South Africa( Anything Fragile = Broken On Delivery ). A driver and diode laser or 3 would be well within budget but as far as I can see, the cheapest CO2 systems are going to set me back at least $200 without anything fancy.

    In all, I was hoping I could use a Diode laser to do the cutting by mounting it directly onto my gantry. (Multiple passes for thicker materilas) and it would occupy a lot less space

    Would this at all be possible with diodes?

    Thanks

  4. #4
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    Can I just throw a note of caution in here...

    If you're cutting any sort of plastics with a source of heat (such as a laser), please ensure you have ventilation and lots of it. Plastics can give off some pretty toxic fumes and you need to get these away quickly, preferably with an extractor at the source of the cut.

    You can thank me for saving your life later lol
    Quote: "There is a theory which states that if ever, for any reason, anyone discovers what exactly the Universe is for and why it is here it will instantly disappear and be replaced by something even more bizarre and inexplicable. There is another that states that this has already happened.... Douglas Adams 1952 - 2001

  5. #5
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    Co2 lasers match a molecular adsorption band in organics, this gives you a very clean cut, that is self polishing in many materials. A Co2 laser + gentle air jet to clean the cut is all you need.

    Diode lasers tend to just melt the plastic, so you would need 100-200 watts of 800 nm diode laser + a very carefully structured and voracious air jet to clean the cut. Edge quality will be not so good.

    In either case, you need a way to dump the fumes overboard, what comes out of a laser cutter is very nasty if your cutting plastics.

    Metal-Ceramic CO2 tubes, ie Synrad, Diamond, Deos, etc... Will survive the trip

    Steve
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  6. #6
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    Ah cool! SA there are a couple of member down your way.

    I found this
    http://hackteria.org/wiki/index.php/...o_Laser_Cutter

    I think 445 will mostly be limited to very thin materials.

    Now I'm speculating here but I think it will be a challenge as the poor beam profile of the multimode blues won't allow you to get high enough W/cm2 in a nice spot and to penitarate very deep.

    I was reading some of the pros and cons of marking/cutting with YAG or CO2 and the absorbsion by different materials was quiet different for both.

    I'm sure you can improve the prospects with cutting with 445 with the right optics combination but it could blow the budget pretty quickly.

    I've got to go to bed but hopefully some more knowledgable folks in the awake time zones will chime in soon.
    Good luck and interested to see how you go.

    Kit

  7. #7
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    Ah, there you go, just the man I was thinking of

    What Steve and Jem said

  8. #8
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    Thanks for the heads up about the fumes

    It looks as though I am going to have to go the CO2 route then, just contacted one of the local suppliers and they charge about $400 for a 40Watt "Reci" tube and $350 for the power supply.

    I am Shocked

    Will do some cost calculations tonight and see what a working budget will be.

    Thanks Guys, never expected so many responses

    Xproximity

  9. #9
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    Hi Xproximity,

    you can find some information on sourcing+usability of diodelasers in the article starting on side 59 in the second issue of the RepRap-magazine:
    http://reprapmagazine.com/issues/2/

    In the next issues I'll post some more infos and application examples.

    Actually I'm developing toolheads based on IR-diodelasers with 9Watts @975nm on a spot of around 0,1mm for cutting/engraving thin sheets of dark plastic or paint and some SLS-applications with plastic powders.

    With time the prices of the higher powered diodes should drop significantly -- actually 9Watts are around 400-500 Euros ...

    Viktor

  10. #10
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    Quote Originally Posted by Jem View Post
    Can I just throw a note of caution in here...

    If you're cutting any sort of plastics with a source of heat (such as a laser), please ensure you have ventilation and lots of it. Plastics can give off some pretty toxic fumes and you need to get these away quickly, preferably with an extractor at the source of the cut.

    You can thank me for saving your life later lol
    +1.

    Many plastics give off cyanide when burned. Others can produce hydrofluoric acid on breakdown (soaks through the skin and decalcifies bones in addition to burning - can be fatal) - very common in the plastics used in car interiors.

    There are a lot of other nasty break down products as well depending on the plastic.

    Fume extraction is a must.

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