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Laser protective acrylic

Discussion in 'Laser Cutters' started by nportelli, Mar 28, 2018.

  1. nportelli

    nportelli New
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    What do people use? And why is it so expensive? Is it because it is tested or special type? I'm looking for a protective sheet for a 445nm diode laser.
     
  2. BNMaker

    BNMaker Well-Known
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    For a 445nm laser, orange acrylic in 3mm will give you ‘adequate’ protection from the odd stray reflection for diodes <3W, but there’s no substitute for glasses and you should still wear them - you’ve only got one spare eye ;)

    The darker the orange tint, the more the protection.

    You can beef up the protection if you have a 3W<8W laser by putting a layer of reflective acrylic ‘one way’ sheet on the inside. The kind of stick-on sheet you would use for an infinity mirror (which is where I got mine - off-cuts from my infinity clock).
     
  3. Giarc

    Giarc Master
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    I bought a piece from jtech photonics because even with glasses, I did not feel the protection was adequate because reflected light would get under the lenses sometimes. The stuff they sell is tested. The shipping is what was expensive, but it came in two days. I looked at Tap plastic's orange acrylic but no data was available so I went with jtech. I need my eyes to make a living - and because I like them. It was worth the $32 IMHO.
     
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  4. Scotty Orr

    Scotty Orr Journeyman
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  5. Giarc

    Giarc Master
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    I am building a box as well. Unfortunately, mine will be much longer since the focal length of my laser is about 180 mm.
     
  6. JustinTime

    JustinTime Journeyman
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    Scotty, is that a cream-cheese/sour-cream tub that is encasing your diode?
     
  7. Scotty Orr

    Scotty Orr Journeyman
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    No, that's my 3D printed router adapter for my Makita - I just leave it in place when swapping out the router for the laser mount.

    20171211_155759.jpg
    20171229_133909.jpg
     
  8. Mark Carew

    Mark Carew OpenBuilds Team
    Staff Member Moderator Resident Builder Project Maker Builder

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  9. BNMaker

    BNMaker Well-Known
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    Yep, you've only got one spare!

    But... orange is orange. These 'laser safety' companies are charging huge money for what is just normal coloured acrylic. They give all sorts of fancy figures, and 'OD' numbers, but what they really do is to buy a bunch of off-the-shelf acrylic and put it through a spectrum analyser - which you can do at home, except the cost of an analyser is more than a sheet of 'laser' acrylic.., but, I just happen to have a transmissive and reflective spectrum analyser and the absorption capabilities of yellow through red acrylic give varying levels of absorption of 445nm light, from over 50% to over 90%.

    And I live in the middle of nowhere in SE Asia, where you can't easily buy 'laser safe acrylic'... unless you want to pay US$150 for shipping of a 12"x12" square.

    There's nothing special about 'laser safe' acrylic - its just coloured acrylic that naturally absorbs a specific range of frequencies of light. Orange is high up on the visible spectrum - around 640-650nm - which means it doesn't transmit other, lower colours, but passes the range we see as orange.

    If you had a blue sheet of acrylic, that's low on the spectrum - 420-470nm, depending on the colour. That would pass a 445nm laser, but block a red diode laser at 640nm

    It very much matters a) what kind of laser - diode vs CO2 b) the power of your laser c) IR or visible spectrum d) the opacity of your acrylic.

    For IR lasers, even a sheet of clear acrylic will block 95% of IR. But a clear sheet won't do much at all for a visible-light diode... and theres a reason black acrylic is easy to cut - it absorbs all the energy and converts it to heat.

    So, don't worry too much about it - if you have a 500mw - 10W 'blue' laser diode, a sheet of 50% orange acrylic will cut down the transmission of harmful rays to a non-harmful level. So will dark sunglasses, but without knowing the colour of the glasses and the frequency of the laser, you are just being stupid to use sunglasses as your primary defence.

    And you can test it yourself - get a piece of acrylic you want to test, set your laser at 90deg to the beam, place a piece of tissue paper or other easily burned object and fire up. You won't even be able to scorch light tissue with the beam focused on the paper.

    Reflection is the major source of stray coherent light beams in unexpected places. And, unless you're cutting or engraving mirrors 0.o then the reflected beam is going to be significantly lower powered than the beam that struck the object. it will also absorb some of the 'speed' of the beam, shifting it to a lower frequency.

    If you want to DIY your laser shielding, get some complementary coloured acrylic and for additional safety some 'one way' reflective film for the inside and you will be fine - but ALWAYS wear your safety specs, even if you have shielding. One accident is all it takes.
     
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  10. Giarc

    Giarc Master
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    I agree with what you are saying. However, for me the decision was that since Tap Plastics was just a few dollars less for orange acrylic shipped to my house then Jtech was, and Jtech took the time to provide me with data I would go with theirs. I could have got the Tap Plastics piece significantly cheaper if I drove to the store, but I started putting a dollar amount on my weekend time and to me it was not worth the gas burned and the hour to hour and a half round trip.
     
  11. BNMaker

    BNMaker Well-Known
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    J tech haven”t made some special plastic - they’ve just sourced good quality orange acrylic.

    Most of the world isn’t within easy driving distance, and the original question was about what works.

    If it is orange, it’s filtering blue light.

    It’s not rocket science.
     
  12. LazrManny

    LazrManny New
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    Hi Scotty & others: I'm new to this forum (joined today!). I have an XY table from a fluid dispensing system and wanted to turn it into a laser engraver. Here's the specification of the 15W Laser Head Engraving Module that I have purchased.
    15W Laser Head Engraving Module 450nm Blu-ray w/TTL Wood Marking Cutting Tool | eBay

    I also have (orange acrylic) Laser Protective Sheets from Polymer solutions with the following specification:
    Polymer Solutions Inc 1019-145 Near VIS Laser Protective Sheet 7" X 11" X .140"
    Uses: Broad-band, cost-effective protection for multiple laser threats in a single environment. Material: Acrylic. Laser Protective Range: OD greater than 5 from 190 to 375 nm, OD greater than 4 from 376 to 533 nm, OD greater than 5 at 1064 nm, OD greater than 4 from 900 to 1070 nm, OD greater than 5 at 10,600 nm. Transmission: 16.5%

    I'd like to build a shield around the laser head using this protective acrylic sheet. Questions:
    i) Is this the right combination of laser wavelength and shielding?
    ii) Could someone please upload a laser engraver wattage chart so I can better understand what my system will be capable of?
    iii) Is LightBurn software absolutely essential to this enterprise? (I already have other means of generating g-code.)

    Best regards,
    Manny
     
  13. Anthony Bolgar

    Anthony Bolgar Journeyman
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    In regards to LightBurn, it is not essential, but it is a lot easier to work with. It is an all in one design and control software package designed specifically for lasers. The Gcode version is only $40, but there is a free trial available at LightBurn Software Give it a try, and if you like using it you can always purchase it. If not, nothing lost.
     
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  14. Giarc

    Giarc Master
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    I have been mulling this one over for my K40. Right now I use k40 whisperer with the stock board.
     
  15. Anthony Bolgar

    Anthony Bolgar Journeyman
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    You would need to upgrade the stock K40 controller to use LightBurn. But it does make it much more versatile. Cohesion3D.com and Awesome.tech both sell drop in plug and play upgrade controllers.
     
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  16. BNMaker

    BNMaker Well-Known
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    The most powerful laser diode made by man is ~7W - anyone claiming a single diode is more is ‘marketing’ to an easily suckered audience.

    As I posted before, any orange/red translucent acrylic will work fine. You can test by firing your laser through the acrylic to rice/tissue paper. You will be unlikely to even scorch it, let alone burn.

    One issue is simply the brightness of the beam - it’s tiring on the eyes and even with protection, you should never look at the beam.

    I’ve built a number of diode lasers and not used a shield with any of them, but you won’t get in my workshop without proper safety glasses.
     
    Rick 2.0 likes this.

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