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Thread: Cutting Acrylic Mirror - preparing for paint

  1. #1
    Join Date
    Sep 2015
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    Default Cutting Acrylic Mirror - preparing for paint

    Hi everyone.

    So, I have several different instances where I am cutting out acrylic mirror shapes, and also, need to "etch" shapes or words into the acrylic coating in order to paint the acrylic. Example attached.

    On that project, I cut a pocket in the coated side of the mirror about .040 deep using a 1/4" O-Flute bit. It came out great!

    These new projects are much smaller, so a 1/4" bit is too large. So, I'm using a 1/8" O-flute and having mixed results. Generally, when pocketing, I have it offset 80% of the bit diameter per pass (so, .1" in this case). The worst results come when choosing "offset". The generated toolpaths end up having some - I guess you would call it - abrupt direction changes, and that leaves small divots in the back of the mirror that show up through the paint.

    When I have manually offset the toolpaths, making sure there were no direction changes or Z-up and Z-down moves during the pocketing, results have been better.

    My question is whether there is a better bit to do the material removal on the back of the acrylic mirror to leave a more uniform surface? Also, do y'all think that "raster" is a better method for toolpathing for this purpose? I'd prefer to not have to create manual toolpaths if I can avoid it (time consuming).

    Thanks everyone!
    Attached Images Attached Images

  2. #2
    Join Date
    Feb 2013
    Location
    River Fall WI
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    Default

    What is your hold down method? Sounds like your material is moving up and down.
    Kyle Stapleton
    River Falls Renaissance Academy
    Math/Technology Education Teacher


    PRS Alpha 96x60 2.2 hp spindle, Double Air drills, 6" indexer, Fein 5 zone vac table
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  3. #3
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    Sep 2015
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    Buford, GA
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    Default

    I have a vacuum system, so it's definitely not that. I even leave of dust collection so that it's not fighting the vacuum. I also recently skimmed the spoilboard.

    It seems to happen when leaving the software to generate the toolpath, and then it sometimes has the z-axis go up, move, go down, and the clear a small portion.

  4. #4
    Join Date
    Jan 2004
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    iBILD Solutions - Southern NJ
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    Quote Originally Posted by BoilermakerAndy View Post
    ...These new projects are much smaller, so a 1/4" bit is too large. So, I'm using a 1/8" O-flute and having mixed results. Generally, when pocketing, I have it offset 80% of the bit diameter per pass (so, .1" in this case)...
    First, set your tool to 40% in the tool database and unless you are cutting something really dense, like aluminum or brass - just leave it there. It is going to be the fastest/most aggressive setting for pocketing without leaving little triangular islands in the corners.

    Second, if you haven't already, go here: http://www.plasticrouting.com/BitSea...?Page=Material and enter in your material (or closest to what you have) and see what they recommend. I do know that Onsrud makes an O-flute specifically for getting a cleaner bottom finish. You're more than likely going to get a better finish using a multi-fluted O-flute vs a single O - spiral or straight. Don't underestimate the advantages of making friends with your local tooling dealer. You'll get better tools at better prices than schmucky retail - plus in many cases the professional answers you need.

    Lastly...Use raster for anything that people are going to see. The offset strategy seems to draw the eye to it - rather than your overall design. It has a regular look to it and is much easier to either camouflage or clean up.
    High Definition 3D Laser Scanning Services - Advanced ShopBot CNC Training and Consultation - Vectric Custom Video Training IBILD.com

  5. #5
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    I've lurked on this forum for some time, and have marveled at you responses, Brady Watson. It is humbling that you responded to my post. Thank you VERY much.

    I do know my local Onsrud supplier, and I will reach out. This is a big help......thanks again..

    Andy

  6. #6
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    Andy
    Glad to help. No need to be humble for me... I'm just a regular guy.
    High Definition 3D Laser Scanning Services - Advanced ShopBot CNC Training and Consultation - Vectric Custom Video Training IBILD.com

  7. #7
    Join Date
    Jan 2004
    Location
    Marietta GA
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    Quote Originally Posted by Brady Watson View Post
    Andy
    Glad to help. No need to be humble for me... I'm just a regular guy.
    With super human cnc powers...

  8. #8
    Join Date
    Jun 2004
    Location
    Springfield Mo
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    Default help

    If you need help Andy... just say "come here Watson, I need you"

    and he comes right over...
    The decimal point seems to be the most important on the z axis... x & y not so much....
    ShopBot... Where even the scraps and things you mess up and throw away are cool....

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