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Trying to get that "Mirror Finish" on cast acrylic with bits only

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  • Trying to get that "Mirror Finish" on cast acrylic with bits only


    Hey guys, just figured I'd ask any of my fellow CNC'ers for some tips.

    So my company has given me a project to create a Case knife-holding-plaque out of a 1" slab of cast acrylic. I've managed to complete a few of these but, I feel that there is an easier way to do it.
    My problem is that I spend about 10 minutes cutting out the plaque, and about 2 hours sanding and polishing it. I'm using an Amana 3/8" O flute at 18k rpm, with a feedrate of 200 ipm, and at a plunge rate at 110 ipm (recommended settings). I sent this with conventional, 3 passes with a final pass allowance of 0.015.
    I've tried a few different final pass settings with all the same end results. Is the bit flute just too large and is taking too many big chunks? I'll have to admit, I've been too scared to play around with feeds and speeds because of my budget (or lack thereof). My shop is very frugal with that sort of thing.
    Anywho, I've posted a few pictures to show the initial marks on the material after I cut it. I'd really appreciate anyone that could take a look and throw me an idea or two.

    Thanks,
    Robot
    Attached Files
  • #2

    You're gonna need a PCD Diamond bit.


    I never used one so couldnt tell ya.

    ooof! I just reread and seen frugal..... "forget about it"

    Flaming the edges is in frugal range

    Comment

    • #3

      I cut a lot acrylic up to 3/4".
      Some suggestions:
      - Make sure work holding is rock solid
      - Try climb cutting
      - Use very sharp new upcut O-flute bits
      - a 1/2 bit will deflect less than a 1/4" bit
      - try not cutting deeper than 1/3 bit diameter

      Should get better finish than you are showing with above so that a light sanding followed by flame polishing will look nice.
      Good luck.
      Pete
      ----------
      2021 Stinger I SR-24, 1kW Spindle
      Performance Pkg w/Gantry Lift, FTC
      Phenolic Top, Storm Vac, JTech Laser
      VCarve Pro 11.0
      www.gotoguysmarine.com

      Comment

      • #4

        Look into acrylic flame polishing with a standard off the shelf propane torch. Quick, simple, and cheap.
        Bruce Page
        Retired Hobbyist
        2013 Stinger 1 SR23
        FTC
        Laser Pointer
        HSD 1.7kw Spindle
        KRS USB Keypad
        Mick Martin Table
        Aspire 10.512, WinCNC
        brucep128@gmail.com

        Comment

        • #5

          Originally posted by UglySign View Post
          You're gonna need a PCD Diamond bit.


          I never used one so couldnt tell ya.

          ooof! I just reread and seen frugal..... "forget about it"

          Flaming the edges is in frugal range
          Haha, diamond bits. That's a good one. I needed a good laugh this morning, thanks for the reply though!

          Comment

          • #6

            Originally posted by gtgmarine View Post
            I cut a lot acrylic up to 3/4".
            Some suggestions:
            - Make sure work holding is rock solid
            - Try climb cutting
            - Use very sharp new upcut O-flute bits
            - a 1/2 bit will deflect less than a 1/4" bit
            - try not cutting deeper than 1/3 bit diameter

            Should get better finish than you are showing with above so that a light sanding followed by flame polishing will look nice.
            Good luck.
            My hold down method are screws directly to my spoilboard, so that should be good. I'll definitely try climb cutting as well as your other tips.

            Thanks!

            Comment

            • #7

              BTW. what machine are you running?
              Pete
              ----------
              2021 Stinger I SR-24, 1kW Spindle
              Performance Pkg w/Gantry Lift, FTC
              Phenolic Top, Storm Vac, JTech Laser
              VCarve Pro 11.0
              www.gotoguysmarine.com

              Comment

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