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blue diode vs co2 laser and wattages, what's the difference?

Discussion in 'Laser Cutters' started by nportelli, Dec 6, 2017.

  1. nportelli

    nportelli New
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    So I'd like to look into a laser cutter...(even though I barely got my OX cnc up and running) What are the differences in the diode blue lasers and co2 tube lasers in cutting power, focus, etc? Of course to the newb like me a 15watt diode sounds better than a 3.5watt or 7 watt one. But I noticed the wavelength of the laser changes. Does that mean it's not a fine? Are diodes focus-able? Are co2 lasers?

    If there is already a post or website that explains off of this already, please post.
     
  2. Jonathon Duerig

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    Generally speaking, the low-wattage diode lasers are more for engraving. They might be able to cut very thin materials, but they are best used to make marks on existing materials. They are small and easily cooled enough that they can be mounted directly onto a gantry (like your OX). They typically range from 2 watts up to 7 watts. Not sure about the 15 watt one. The ability to cut or engrave is not linear in the number of watts partly because the high-wattage ones can't maintain their peak wattage and partly because there is a relatively narrow focus area regardless of the power.

    The high-wattage CO2 lasers (and fiber lasers) are powerful enough to cut through materials. They are too large to mount on a gantry in a reasonable way, so they are typically mounted in a static location with mirrors placed at various points to direct the laser beam downwards through a lens as the gantry moves. They go from 15 watts up to 150 watts (or up to kilowatts for industrial lasers). At 150 watts, it can cut through quarter-inch plywood or possibly even a bit thicker depending on many different details.

    Both kinds of lasers are potentially hazardous to your eyes (always wear eye protection or use an enclosure or both). They will cause major damage to anything you point them at. They are invisible. The high wattage CO2 lasers also use a large amount of power and must have an active cooling system. There is also electrical danger on the high wattage CO2 lasers because high wattage means a shock can be very bad for you.

    -D
     
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  3. RussB

    RussB Well-Known
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    Great, simple description :) Well done!
     
  4. Rendermandan

    Rendermandan Veteran
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    Is there some type of chart that has laser power vs speed vs thickness etc to cut different material types?
     
  5. nportelli

    nportelli New
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    So why does a co2 laser cut through thicker material?
     
  6. Jonathon Duerig

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    @Rendermandan There is no standard chart AFAIK. Part of the reason is that there seem to be a lot of variables including the quality of the components, quality of materials, and how focused (and energy dense) the actual laser is. So a cheap import laser at 90w might not cut as well as a 'big name' laser at 90w. And the power curve on all CO2 lasers goes down as time passes, so they need to be replaced periodically.

    @nportelli Because at a hobby level, all diode lasers are low power (2w - 7w) while CO2 lasers are much higher power (12w-150w). So if you want to do cutting, make sure to get a higher power machine. It is often hard to compare different manufacturers. But if you look at the same manufacturer, you can be sure that a 90w laser will cut much better than a 50w laser and a 150w laser will cut even better.

    -D
     
  7. nportelli

    nportelli New
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    I figured the different wavelengths attributed to the power needed for the lasers. ie a 6 watt blue laser with smaller wavelength has as much power as a 40 watt red laser. But maybe it doesn't work that way.
     
  8. Jonathon Duerig

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    AFAIK, the wavelength only affects which materials are transparent or opaque. So one reason why CO2 lasers can't cut through aluminum or steel and even have trouble marking them at 150 watts is because the wavelength of CO2 lasers mostly passes through them. And the laser marking spray is stuff that is opaque to lasers and therefore fuses with the metal when lasered to create a permanent mark.

    There are many manufacturers that claim that some special aspect of their laser technology lets them have more effective power than others of comparable wattage. But it is often hard to assess these claims except that the 'random no-name' 90 watt is likely to not cut as well as a 'big name' 90 watt.

    -D
     
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  9. nportelli

    nportelli New
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    Interesting. I suppose my main question is would a diode laser be able to cut thin plywood? With multiple passes perhaps?
     
  10. Jonathon Duerig

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    @nportelli It is possible to cut thin plywood with a lot of passes using only a diode laser. Emphasis on thin. You will want to buy high quality plywood. There is even plywood especially made with a kind of glue and lack of voids that makes it easier to cut with a laser, so get that stuff if at all possible. IIRC, outdoor plywood has glue that makes it really hard to laser.

    Then you need to expect to make a lot of passes. And you will be best served if you have a z-axis on your gantry so each pass can focus the laser at a slightly lower spot on the plywood.

    And you will want compressed air if possible to blow away dust and ash and smoke.

    And the edge will likely be quite charred and a relatively rough cut.

    With all this, it is probably able to cut in a pinch if all you have is the diode laser. But really the diode laser is best suited for engraving. Look for 'plywood' or 'wood' on this page for example:

    Applications | J Tech Photonics, Inc.

    I picked up a diode laser system myself recently. My plan is to use it exclusively for engraving and leave the actual cutting part to my CNC router. With good registration, that should be better option.

    -D
     
  11. JustinTime

    JustinTime Master
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    Rob Saunders said that he cut through thin plywood and even 1/2" poplar! Read here: Laser Cutter/Engraver OptLaser 6W with Z-axis
     

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