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Thread: help Cutting 1/2" cast acrylic,

  1. #1
    Join Date
    May 2008
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    Fennimore, Wi
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    help Cutting 1/2" cast acrylic,

    Im new to the forum, from what I see this is a good place for advice. I consider my self to be a newbee with the laser, had it about a year and a half, have gotten pretty good but have alot to learn. GCC Laser pro spirit 40W.
    Her is what i need advice with.
    Had a new possible customer ask me to cut 1/2" cast acrylic, clear, he is looking to sub out the pieces as he now cuts them on a cnc but has to polish the edges clear after. He is hoping a laser will cut them clean and clear. Talking with him, if i can do it it would be 100 pieces per order, 6-10 orders per year. 2" x4 1/2" funny shaped pieces. It would be good for me.
    Spent yesterday working on the settings, laser cuts through just fine, trying to get it tuned in.
    So far the best settings I found is .1 speed, 30 power, 1000ppi, and i moved the table up .070" into the piece.
    I have the lens that comes with it, 2"
    With this I am getting a pretty good result however, and this is hard to explain so bear with me. Watching the laser cut ther is a "wave effect" as the beam cuts. the bottom of the cut lags behind the top of the cut. I assume this is due to the thickness of the acrylic. I can speed up but the lag gets worse which causes the corners to not cut well.
    I would like to speed up to keep cost reasonable. Can I?? Different lens, focus closer??? Any other opinions or advice would be very appreciated.
    Thanks Chad,
    Chad Fitzgerald
    Hickory Grove Cabinetry
    Custom Woodworking/Laser Engraving
    Laser Pro Spirit 40W
    ShopSabre RC4 CNC
    55x49 cut area
    with 3 1/4 PC Router, 10" Z

  2. #2
    Yes, those that have cut thick acrylic know exactly about that flowing wave you talk about. The answer is, you can't speed it up. You need more power to speed it up and 40W is at the outside edge of being able to cut 1/2" acrylic, in my opinion, much less cut it efficiently.
    Lasers : Trotec Speedy 300 75W, Trotec Speedy 300 80W, Galvo Fiber Laser 20W
    Printers : Mimaki UJF-6042 UV Flatbed Printer , HP Designjet L26500 61" Wide Format Latex Printer, Summa S140-T 48" Vinyl Plotter
    Router : ShopBot 48" x 96" CNC Router Rotary Engravers : (2) Xenetech XOT 16 x 25 Rotary Engravers

    Real name Steve but that name was taken on the forum. Used Middle name. Call me Steve or Scott, doesn't matter.

  3. #3
    Join Date
    Feb 2007
    Location
    Alabama
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    2,395
    Quote Originally Posted by Chad Fitzgerald View Post
    Im new to the forum, from what I see this is a good place for advice. I consider my self to be a newbee with the laser, had it about a year and a half, have gotten pretty good but have alot to learn. GCC Laser pro spirit 40W.
    Her is what i need advice with.
    Had a new possible customer ask me to cut 1/2" cast acrylic, clear, he is looking to sub out the pieces as he now cuts them on a cnc but has to polish the edges clear after. He is hoping a laser will cut them clean and clear. Talking with him, if i can do it it would be 100 pieces per order, 6-10 orders per year. 2" x4 1/2" funny shaped pieces. It would be good for me.
    Spent yesterday working on the settings, laser cuts through just fine, trying to get it tuned in.
    So far the best settings I found is .1 speed, 30 power, 1000ppi, and i moved the table up .070" into the piece.
    I have the lens that comes with it, 2"
    With this I am getting a pretty good result however, and this is hard to explain so bear with me. Watching the laser cut ther is a "wave effect" as the beam cuts. the bottom of the cut lags behind the top of the cut. I assume this is due to the thickness of the acrylic. I can speed up but the lag gets worse which causes the corners to not cut well.
    I would like to speed up to keep cost reasonable. Can I?? Different lens, focus closer??? Any other opinions or advice would be very appreciated.
    Thanks Chad,
    I'm surprised you can cut it with 30 power on a 40 watt machine ! I never use anything less that 100 power and 5000 frequency for acrylic. I have never attempted 1/2", although I have seen other posts from folks with a 40 or 45 watt machine say it can be done. 4" lens maybe?
    Epilog Legend EXT36-40watt, Corel X4, Canon iPF8000 44" printer,Photoshop CS6, Ioline plotter, Hotronix Swinger Heat Press, Ricoh GX e3300 Sublimation

  4. #4
    Join Date
    Jun 2012
    Location
    Quebec, Canada
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    Hi Chad,
    Wow, 1/2" with a 40W laser, hummm, not sure
    I have a 60W and for me 3/8" is about the max for a good result.
    Yes I can do 1/2", but I am not satisfy 100%, but some customers are OK with that
    But I must say that I am very fussy with the quality
    I'm just surprise that you use only 30% of your power
    I'm still a newbie, but when I cut out 1/2" I use 100% of the power of my 60W
    Then, I adjust my speed very slow and I put water on the back of the material
    I don't know about GCC cuz I use Trotec, setting r differents
    For me, believe it or not I can do a pretty nice job with a 1.5 lens with a tickness of 1/2"
    Not perfect but not bad too
    I'd try with more power if I were you
    And with my 60W, I know it would take about 2 minutes for a rectangle of 4-1/2" X 2"

    Best of luck to you
    As a newbee this is my best advice
    Hope you will get better

    Michel
    Trotec Speedy 300 60W

  5. #5
    Join Date
    May 2008
    Location
    Fennimore, Wi
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    I was surprised also, i started with more power but melted the acrlic and burnt the heck out of the paper on the bottom. Still working on it, I sure appreciate the comments, more is better. Any help is appreciated.
    Chad Fitzgerald
    Hickory Grove Cabinetry
    Custom Woodworking/Laser Engraving
    Laser Pro Spirit 40W
    ShopSabre RC4 CNC
    55x49 cut area
    with 3 1/4 PC Router, 10" Z

  6. #6
    Join Date
    Mar 2011
    Location
    Olalla, WA
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    1,532
    Iv'e cut quite a bit of 3/8" acrylic and some 1/2". The best results have been with a 2.5" lens and 4mm/s, 80% power (80 watt Reci). This gives the best edge quality for me. I can cut faster (5mm/sec, 90%) but then the bottom third of the cut then starts to get the little coin-edge ridges. If the edge quality is not an issue I can cut at 6mm/sec, and a bit faster if only the upper left part of the table is used.

    I found no benefit to using a 4" lens, and the 2" lens did not cut any nicer either. If I had more power then I think a 4" lens would work better.

    I also use a LOT of air assist.
    Shenhui 1440x850, 130 Watt Reci Z6
    Gerber Sabre 408

  7. #7
    Join Date
    Jun 2012
    Location
    Quebec, Canada
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    Hi Chad,
    Try to remove the paper on both sides
    and put transfer tape under and I spray with a lot of water
    It helps a lot for me
    I'm still newbie but this is helpful for me

    good luck,

    Michel
    Trotec Speedy 300 60W

  8. #8
    Michel

    You would get better results from a 2" lens or longer.
    Mike Null

    St. Louis Laser, Inc.

    Trotec Speedy 300, 80 watt
    Gravograph IS400
    Woodworking shop CLTT and Laser Sublimation
    Dye Sublimation
    CorelDraw X5, X7

  9. #9
    Join Date
    Oct 2004
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    Cape Town, South Africa
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    This isn't the right tool for this job , my advise is to pass on this one - I would as I KNOW it's going to become a costly PITA.
    Rodney Gold, Toker Bros trophies, Cape Town , South Africa :
    Roland 2300 rotary . 3 x ISEL's ..1m x 500mm CnC .
    Tekcel 1200x2400 router , 900 x 600 60w Shenui laser , 1200 x 800 80w Reci tube Shenhui Laser
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    1600mm hot and cold laminator , 3x Dopag resin dispensers , sandblasting setup, acid etcher

  10. #10
    Join Date
    Jun 2012
    Location
    Quebec, Canada
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    Hi Mike,
    I have 2 lens, 1 is 1.5 and the other one is 2.5, don't have the 2"
    I tried the 2.5 already but i'm not very happy with results.
    May be my focus is not adjust good...
    I am pretty impress with the result of the 1.5, more than 2.5
    I know I should have to get better with the 2.5, may be I should verify the focus tool again.
    Anyway, Thank for your advice

    Best regards

    Michel
    Trotec Speedy 300 60W

  11. #11
    Michel

    You may have this already but if not cut what you need form 1/8" thick acrylic.

    Focustools_Speedy2_300_Finemarker.cdr
    Mike Null

    St. Louis Laser, Inc.

    Trotec Speedy 300, 80 watt
    Gravograph IS400
    Woodworking shop CLTT and Laser Sublimation
    Dye Sublimation
    CorelDraw X5, X7

  12. #12
    Quote Originally Posted by Chad Fitzgerald View Post
    . . . Watching the laser cut ther is a "wave effect" as the beam cuts. the bottom of the cut lags behind the top of the cut. I assume this is due to the thickness of the acrylic. I can speed up but the lag gets worse which causes the corners to not cut well. . . .
    What you are seeing is called "striations" and the laser is behaving exactly as normal. The faster you move the beam the more pronounced the striations will be. Search on "striations" and "laser cutting" if you want more info.

    Are you sure you are using 30% power? I realize you are cutting very slow but I'm also surprised you can punch through at all especially at 30%. What happens to the cut quality when you bump up the power to 100%?

    I don't know if you can make this viable if you have to cut at .1% speed but if you can be competitive then that is great. Unfortunately this really calls for a much higher-powered laser. (100 or 200 watts I would think.)
    Attached Images Attached Images

  13. #13
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    I agree with Rodne on this one. The discussion is if it's technically feasible which can become an obsession. You do need to weigh very heavily if it's financially feasible.
    Tim
    There are Big Brain people & Small Brain people. I'm one of the Big Brains - with a lot of empty space.- me
    50W Fiber - Raycus/MaxPhotonics - It's a metal eating beast!
    Epilog Fusion M2 50/30 Co2/Fiber - 2015
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  14. #14
    Join Date
    May 2008
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    Fennimore, Wi
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    Ok, just ran it again to double check my settings, .1S, 30% power(40W laser), 1000ppi, .070 focused into the piece. 1/2" cast clear acrylic. I know the 30% sounds wierd, i agree, but thats what it is.
    just cut a 1/2 x 3/4" oval. edge is almost perfect except, pronounced "striation line" at the start stop spot, very small hardly noticable, and a very slight "bevel" around the bottom side of the piece.
    if i turn up the power it melts, sizzles, in the cut, flames terrible underneath. if i speed it up the wave effect gets worse and make a poorer cut.
    I agree with everyone at this speed it will not be financially feasable. Was hoping to speed it up since i have plenty of power left to use.
    My tech rep suggested more air/exhust flow would allow more power and speed with out the flames/melting. theory being the fumes are giving the laserbeam fuel to burn. Thoughts on this?
    I understand it just may not work and appreciate ALL the advice and suggestions. I sometimes have a hard time letting go when im close.
    thnaks
    Chad Fitzgerald
    Hickory Grove Cabinetry
    Custom Woodworking/Laser Engraving
    Laser Pro Spirit 40W
    ShopSabre RC4 CNC
    55x49 cut area
    with 3 1/4 PC Router, 10" Z

  15. #15
    Join Date
    Oct 2004
    Location
    Cape Town, South Africa
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    We would have our air assist nozzle pointed at the cut and would have it turned up to a VERY angry hiss with air velocities at force 9 on the beaufort scale.
    Rodney Gold, Toker Bros trophies, Cape Town , South Africa :
    Roland 2300 rotary . 3 x ISEL's ..1m x 500mm CnC .
    Tekcel 1200x2400 router , 900 x 600 60w Shenui laser , 1200 x 800 80w Reci tube Shenhui Laser
    6 x longtai lasers 400x600 60w , 1 x longtai 20w fiber
    2x Gravo manual engravers , Roland 540 large format printer/cutter. CLTT setup
    1600mm hot and cold laminator , 3x Dopag resin dispensers , sandblasting setup, acid etcher

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