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  1. #1
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    Dry Machine Aluminum?

    I've been pouring over Bob Warfield's wonderful site www.cnccookbook.com for the last week. He talks about dry machining aluminum, but it seems his definition of dry is "not flood". I'd like to machine aluminum actually dry and wonder how I should change my feeds and speeds in G-Wizard? From reading Bob's post it seems like I should alter my SFM, but by how much when completely dry is not spelled out.

    I will be taking 0.05 WOC, .1875" DOC passes through 6061 with a 3 flute 3/8" endmill made for Aluminum at my roughing stage. G-Wizard suggests 49 IPM @2000RPM on my X3 mill. Any suggestions for a better IPM or DOC (WOC is fixed in my setup)? Can I really run that fast dry?

    Attached is a picture of my project for this weekend:
    Attached Thumbnails Attached Thumbnails AR_15_render.JPG  

  2. #2
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    You gotta show that off after this weekend!! I'm wanting badly to do an AR-10 myself. Gonna be one of my CNC projects when I get it going.

  3. #3
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    In my experience the 2 biggest problems with cutting aluminum without coolant are buildup on the cutting edge and clearing chips. You need to use some type of lubricant to prevent the buildup of aluminum on the cutting edge. I have used small amounts of WD40 succesfully. You also need to remove the chips from the cutting path as they will get pushed through the cut again and mar the surface finish. You could use a vacuum to remove the chips and then small amounts of wd40 sprayed on to keet the edge lubricated. Cooling really isn't that big of a problem on aluminum unless you want to cut at very high spindle speeds.

  4. #4
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    What you describe above is EXACTLY how I do most of my aluminum cutting - a few squirts of WD-40 at the start to the process and vacuum up the chips every few minutes. You do get some roughness on the edges if you don't vacuum frequently enough but for quick stuff this has worked really well for me on the X2.

    -Mike

  5. #5
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    To give you an idea of what you can get away with on 6061, I have a flashcut 6500 and found I could take full with of cut 0.035 " doc at 15,000 rpm @ 35 ipm with a 2fl 1/4" carbide end mill I picked up at homedepot .
    If you want to machine dry 7075 works with no chips sticking to the part like 6061

  6. #6
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    with a 2fl 1/4" carbide end mill I picked up at homedepot .
    Wait...HD sells endmills?!?

    wow i will have to check it out...
    http://www.g0704.blogspot.com/

  7. #7
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    A router bit rather than an endmill I suspect

  8. #8
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    Quote Originally Posted by webgeek View Post
    A router bit rather than an endmill I suspect
    I kinda thought the same... i really wish i had a local vendor I could walk in and buy machine tools...but seems theres is not much in my neck of the woods...I really hate internet orders...
    http://www.g0704.blogspot.com/

  9. #9
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    ya it is a 2 fl up sprial router bit . I didn't want to wait for an order from duramill other wise I would have used that . point is I used junk tooling at high rpm and no melted tool in work pice !

  10. #10
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    Feb 2006
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    For dry cutting, keep the same SFPM as for any other cutting. Calculate feedrate based on the manufacturers maximum recommended chipload (typically on the order of 0.004-0.005" for a 1/2" HSS endmill), and do a shallow cut. Go progressively deeper until either the spindle starts to bog down, vibration gets excessive, or the tool starts clogging. I can cut 0.125" deep, 1/2" slotting, at over 30 IPM with HSS. If you get clogging, INCREASE the feedrate. The tool gets hot when you feed too slow. When you feed fast, the chips will come off VERY hot, and the tool will stay cool, until you get into pretty deep cuts.

    G-Wizard does an excellent job of calculating the best-case cuts you can do. I would start with its recommendation, but a shallower cut, then sneak up on the final depth you want, to make sure the machine can handle it. This will avoid tool breakage.

    Regards,
    Ray L.

  11. #11
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    Thanks for the suggestions (especially Ray). I'll start off with running at the full speed that GWizard says I should run, but use 75% of the cut depth I calculated with. If that goes well, I'll push up the cut depth and see how things go. Thanks!

  12. #12
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    Quote Originally Posted by Kingjamez View Post
    I've been pouring over Bob Warfield's wonderful site www.cnccookbook.com for the last week. He talks about dry machining aluminum, but it seems his definition of dry is "not flood". I'd like to machine aluminum actually dry and wonder how I should change my feeds and speeds in G-Wizard? From reading Bob's post it seems like I should alter my SFM, but by how much when completely dry is not spelled out.

    I will be taking 0.05 WOC, .1875" DOC passes through 6061 with a 3 flute 3/8" endmill made for Aluminum at my roughing stage. G-Wizard suggests 49 IPM @2000RPM on my X3 mill. Any suggestions for a better IPM or DOC (WOC is fixed in my setup)? Can I really run that fast dry?

    Attached is a picture of my project for this weekend:
    For my CNC machine, I found I had to drastically cut the cut depth when dry machining aluminum. I broke 8 1/4" HSS end mills finding the approximate ratio and debugging my own issues. make your cuts really light. And dont walk away if you aren't clearing chips. As the cuts got deeper they caused a lot of heat to condense on the cutter. As the bit heats up it can still dig and break. I ran a hose to my air compressor and it did wonders, but my "flood coolant" system is ready and can't wait to see how much more/smoother I can cut or how much longer I can make my end mills last.

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