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Upcut or down

Discussion in 'CNC Routing & Laser Cutting' started by OADesign, Mar 22, 2007.

  1. OADesign

    OADesign Active Member

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    Jan 27, 2006
    California
    Hi all,

    i am running an older Gerber Dimension 200. We make ADA signs (cast acrylic / braille etc) The guys here have always used single flute upcut spirals. I and thats what i use, just because thats what i was trained to do. but it seems every run, we lose 1-2 parts due to them slipping (dbl side tape hold down). After a convo with a local onsrud distributor and do some online research im finding that we may benefit from using down cut spirals instead. we cut mostly cast acrylic 21000 rpm at about 25-30ipm. edges come out "okay" but im thinking there got to be a way to cut faster and get nice clean edges at the same time.

    any thoughts?
     
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  2. zuboltz

    zuboltz Member

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    Sep 26, 2006
    minneapolis
    Fellow ADA signmaker

    We have a gerber 408 and use masking to hold parts in place and cut with a .188 O flute at about 150 ipm. at 18,000 rpm for 1/8" thick.
    It seems to work for us, great edges.
     
  3. andy

    andy Active Member

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    Aug 19, 2004
    Single flute ground to cut upwards work for me. Tried downcutting 2 flutes and there were issues with weld back as the chippings are forced down onto the bed not up into the extraction.

    I've never found a way to cut fast and clean at the same time. My feed rates for larger shapes are around the same as yours. Smaller parts I run down at 12ipm or lower- depending on the size and shape.

    21,000 rpm sounds way to fast to me. My acrylic brand (Perspex) has a rated optimum RPM of between 16 and 18,000 rpm. I find 16,000 works great- no weld back or gumming up.

    If you have vac hold down it helps a lot. Tabbing strategy in your toolpathing helps on some shapes.

    I always find milling the acrylic at a slow speed rather than trying to blast through it at a high speed usually gives a much nicer finish and reduces pop outs and wasted parts. Sometimes less haste does mean more speed.

    I don't use Onsrud's or other big name brand bits so I don't know if the extra cost of these means you can wizz along faster. I buy some really nice solid carbide bits in bulk so I have a stock of new cutters- some more intricate work gets a new cutter just for that job.
     
  4. Garfield_Graffix

    Garfield_Graffix Member

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    Jul 7, 2006
    Same but different problem

    I am used to cutting Polycast acrylic up to .75" thick. I use a single flute bit upcut. I usually run 18000RPM and 15 to 30 ipm. Oh multicam 48+ router. I got a BIG 2sided sign that calls for acrylic push through letters in an aluminum face. I have tried al day to get started, broke 3 bits because the material wants to collect up in a big wad on the bit and once the flute is clogged it just melts throught the material and ruins it. this stuff is $400 + a sheet and I have little to no room for error. what is causing this build up? I have tried 10000 to 18000 RPM in 500RPM increments and ran 5 all the way to 40 ipm and it does it at all speeds. These are just letters in a plain jane font no tricky shapes so I feel like it should be a no problem situation but its driving me NUTS not to mention boss wants it done yesterday! We usually work half day on friday but now it looks like Ill be here saturday:( What is the deal ? Is slower RPM and IPM required or Higher values for each? AAAAAGGGGHHHHH!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
     
  5. OADesign

    OADesign Active Member

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    Jan 27, 2006
    California

    are you trying to cut this tuff in one pass?
    try cutting in 3 pass of .25 each. or six passes at .125...
     
  6. mtmdesigns

    mtmdesigns Active Member

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    Jun 23, 2006
    OA is 100% correct. Onsrud spiral o .25 u need to run 150, 50, 24000.
    You need to run atleast 3 passes and then run it over with one pass and it should cut clean.
     
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