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Cutting Sintra

Discussion in 'Laser Cutters' started by GVP, Dec 10, 2013.

  1. GVP

    GVP Active Member

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    Nov 11, 2005
    Swift Current, SK
    Greetings,

    Does anyone have any tips regarding cutting out simple flat panels of 1/8" Sintra?

    I'm finding if I use an up-spiral bit, it lifts the material off the bed in places and can cause the shape to come away, often hitting the bit and ruining it.
    If I use a down-spiral, the kerf fills up with the chips and often re-welds itself back together. Perhaps I need better feeds/speeds? Currently around 16000rpm & 125ipm using a 1/8" bit.

    Any suggestions appreciated - we don't have a vacuum hold-down and clamp everything down.

    Thanks,
    Graham
     
    Tags:
  2. letterman7

    letterman7 Very Active Member

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    125ipm? You sure about that? Way, way too fast if it is. Back it down to 2, maybe 3 ips depending on your machine. Are you using a climb cut or conventional with the upspiral? Try cutting the opposite way with the upspiral and see if that changes anything.
     
  3. Techman

    Techman Major Contributor

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    compression bit.
    Up cut on the lower side down cut on the upper side..
     
  4. J Hill Designs

    J Hill Designs Major Contributor

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    Just checking my math here, but doesnt 2 IPS = 120 IPM?!?
     
  5. Z SIGNS

    Z SIGNS Very Active Member

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    Glue it down to a sacrificial sheet of coro and use tabs if need be.
     
  6. Ditchmiester

    Ditchmiester Active Member

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    Use a straight O Flute From Onsrud, They cut with no up or down pressure. I cut plastics with them all day long. I love them. I run about 12K RPM and 100IPM.
     
  7. SebastienL

    SebastienL Active Member

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    one pass with the up cut, leave .025" on the bottom(Don't break thru) and .025" on the wall. Finish with the downcut.
    Upcut will evacuate chip better, Downcut will leave a cleaner edge on top.
    If it's very small part.... Transfer tape on the back, Spray "3M Super 77" or equivalent glue on the tape. Just peel off after cutting.
     
  8. letterman7

    letterman7 Very Active Member

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    :Big Laugh yes it does... I read his post as IPS instead of IPM..
     
  9. synergy_jim

    synergy_jim Very Active Member

    1/8" 2 flute straight - 2 pass - 300 ipm 18000 rpm

    1/4" 2 flute straight - 1 pass - 400 ipm 20000 rpm

    1/4" 2 flute downcut spiral - 400 ipm - 20000 rpm



    The enemy of thin plastic is any upcut bit.
     
  10. synergy_jim

    synergy_jim Very Active Member

    also.... the worst thing you can do on a cnc cutting PVC is run to slow. the second worst thing is bad bit selection.
     
  11. fixtureman

    fixtureman Member

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    I use a .125 single flute up spiral bit at 10000 and 4.5 IPS
     
  12. johnnysigns

    johnnysigns Very Active Member

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  13. fixtureman

    fixtureman Member

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    I also use a pressure foot at times to keep it down
     
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