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  1. #21
    Okay I have had another play.

    I secured my Z axis properly to the X axis(!) and also made a kind of extender tube to get the vacuum suction closer to the work piece. I then tried a cut, but this time I reduced the spindle speed. I used GWizard to receommend a feed and speed and I noticed that actually it was giving me a smaller chipload than recomended. I suppose it was trying to keep tool deflection as low as possible but I found I could reduce the spindle RPM and still keep deflection below the problem area. GWizard sugested (for a 2flute 3.17mm bit) 1mm passes with 2000mm/min and 22,000RPM. I reduced this to 17,000RPM and kept the rest the same.

    The cut is clean, but does have a slight texture, is this about as good as you guys are getting or should I still aim for higher?






  2. #22
    Tom J's Avatar
    Lives in Melksham, United Kingdom. Last Activity: 2 Weeks Ago Has been a member for 3-4 years. Has a total post count of 148. Received thanks 7 times, giving thanks to others 18 times.
    Just broke last carbide single flute 1/8" 3.175mm bit doing 700mm/min at 10.000 rpm, 600mm/min was ok but still poor finish.

  3. #23
    Rye's Avatar
    Lives in Sheffield, United Kingdom. Last Activity: 1 Week Ago Has been a member for 2-3 years. Has a total post count of 36. Received thanks 3 times, giving thanks to others 0 times.
    I usually cut acrylic with 1 mm passes using a 3.175mm single-flute @ 1050 mm/min - somewhere between 10000-13000 rpm (i think). Will be cutting some tomorrow. Will post RPM here.
    Bought a Chinese 6040...if only I'd known better :(

  4. #24
    Tom J's Avatar
    Lives in Melksham, United Kingdom. Last Activity: 2 Weeks Ago Has been a member for 3-4 years. Has a total post count of 148. Received thanks 7 times, giving thanks to others 18 times.
    Quote Originally Posted by Rye View Post
    I usually cut acrylic with 1 mm passes using a 3.175mm single-flute @ 1050 mm/min - somewhere between 10000-13000 rpm (i think). Will be cutting some tomorrow. Will post RPM here.
    I follow 50%+ rule of DOC which was 2mm in for 1/8" will try less. Going to buy decent Trend bit 1/4" 6.35mm

  5. #25
    Several mentions of "Climb V Conventional" in this thread.
    If you are cutting a slot when profile cutting a part there is no climb and conventional, the cut direction only affects the deflection direction toward or away from the part, the cutter is cutting both climb and conventional in alternate halves of it's rotation.
    Climb V Conventional only comes in when the cutter is engaging less than 100% of it's width in material,

    - Nick
    You think that's too expensive? You're not a Model Engineer are you? :D

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  7. #26
    Rye's Avatar
    Lives in Sheffield, United Kingdom. Last Activity: 1 Week Ago Has been a member for 2-3 years. Has a total post count of 36. Received thanks 3 times, giving thanks to others 0 times.
    Quote Originally Posted by Tom J View Post
    I follow 50%+ rule of DOC which was 2mm in for 1/8" will try less. Going to buy decent Trend bit 1/4" 6.35mm
    Cut some 4mm acrylic today using a 4mm shank/3 mm dia cut single-flute shop-apt bit. Did two passes @ just under 2mm on each with a finish pass. Feed rate 1200 mm/min with spindle speed around 13200 rpm (220 hz). Cut fine leaving a nice finish (just a couple of tool marks on one side.) Not saying that's the correct or optimal speed, but it worked for me. Usually I stick to smaller passes because I have a habit of not properly sticking/securing the acrylic to the spoil; and there's nothing worse than spending ages engraving acrylic just to have it lift from the table when cutting :)
    Bought a Chinese 6040...if only I'd known better :(

  8. #27
    Quote Originally Posted by Tenson View Post

    I'm also considering getting a more suitable tool for cutting plastics. Looking at the Cutwell Tools site.. what do you think is better for acrylic they have 45deg Helix flutes (do these extract the chips better?) plus some YG single flute HSSE and some Karnasch cutters. Are the Karnasch worth the extra money?
    I've just bought a 2mm single flute cutter from cutwel last week for cutting acrylic, 10mm think stuff and ran at 24k 2000 feed 1.5mm DOC the finish is fine but needed some 400 wet&dry treatment not a great deal though.

    I didn't bother with a finish pass no real need when I was polishing the edge anyway, it cost 32 or 34 and like a tool it slipped from the collect and lucky as I am hit a metal bolt I use to hold the spoil board down :( still cuts ok but not the same :(

    Top tip before undoing the collect nut put a silicon boot on the cutter :)

    But I've now change the profile method and use a larger dia cutter 10mm doc taking a finish pass, the edge is spot on, no wet&dry treatment and can be buffed to a shine straight on the buffer.

    Can't be seen very clear but the finish is flawless using my new method, I now use the 2mm bit for rapid removal rate and semi finished profile.



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