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Lip on Aluminum Cut

Discussion in 'CNC Routing & Laser Cutting' started by Marty Thompson, Dec 7, 2020.

  1. Marty Thompson

    Marty Thompson New Member

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    Jun 11, 2020
    Rossville, GA
    We cut a piece of 1/8" aluminum and it is leaving a raised lip around the edges on either side of the aluminum. My thought is that my operator used an upward cut bit instead of a downward cut bit or is cutting it too fast. Any insight would be appreciated.
     
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  2. Boudica

    Boudica Active Member

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    This would always happen back when we had to cut ACM by hand. Back then we would pull out the sander and smooth it down.

    Then along came our awesome substrate cutter - which cuts nice and smooth with no sharp lips.

    ...are you covering it with vinyl or direct printing? back in the sanding days - that was also before our flat bed and we did not have direct-print capabilities. so that only works if your going to cover it with vinyl.
     
  3. rossmosh

    rossmosh Active Member

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    It's likely the bit isn't as sharp as it should be. Could also be a settings issue.

    As far as down-cut vs up-cut, generally speaking you cut aluminum with an up-cut. If you cut with a down-cut, the chances of the kerf getting packed and the aluminum chips welding to the bit go way up. Great way to snap a bit and destroy your part.
     
  4. Gino

    Gino Premium Subscriber

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    Are you talking 1/8" sheet aluminum or just 3mm composite board ?? Either way, just use a piece of round metal and slide it down the side and it'll take all the burrs off in one or two passes.
     
  5. James Burke

    James Burke Being a grandpa is more fun than working

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    Shouldn't matter if it's an up-cut or down-cut, but if you make a .005" climb-cut finish pass, it will greatly reduce it to a very manageable burr to file off.

    ALL cutters will leave burrs, it's just their nature. Severe burrs are typically created when you 1) take heavy cuts 2) have a dull cutter 3) feed rate is too fast or 4) you are running too low RPMs.

    (Nearly 40 years in the tool and die trade)

    JB
     
  6. Rick Tennyson

    Rick Tennyson Member

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    Try a new bit, confirm everything. Make sure the spindle is turning the correct way, etc. You should not have to touch it after it gets off the table. Our table runs 18hrs a day. Everything looks and feels like it was cut with a razor blade. Good luck mate!
     
  7. signage

    signage Major Contributor

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    Could be that your spindle isn't perpendicular to the table in both x and y directions.
     
  8. Marty Thompson

    Marty Thompson New Member

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    Jun 11, 2020
    Rossville, GA
    Thanks for all the insight, I will start with a new bit and check the speed rate and the RPM's and go from there.
     
  9. JBurton

    JBurton Signtologist

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    Directionality of the cutter in addition to what everyone else said. Check your drop. If it is a nice finished looking cut, you may be running the bit around the material backwards. Belin 33317A is a single flute, up cut, .125" diameter cutter that is designed to run around the part clockwise.
     
  10. James Burke

    James Burke Being a grandpa is more fun than working

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    Otherwise known as climb-cutting. Most industrial CNC milling is done climb-cutting. Machines with worn ball screws, however will have issues due to backlash (hopping & jumping along as the cutter pulls the material along).


    JB
     
  11. 2ny

    2ny Member

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    Jan 2, 2012
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    Do you use any coolant when you cut? We use alcohol cooling to get a smooth finish, and we also use several passes to get a better finish on the edges.
    Our tool supplier has mills made for dry milling in aluminium also, but we have not tried that type yet.
    I find that the regular type is better when I have to sharpen them from time to time.

    Best regards
    Tony
     
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