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Thread: Cutting 1" thick aluminum on CNC

  1. #13
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    Default Re: Cutting 1" thick aluminum on CNC

    Quote Originally Posted by wizard View Post
    This fact from Jim is very important, rven two flute center cottong end mills dont like to be plunged directly into the work. Use some sort of interpolation.
    I countersink holes in aluminum all the time this way on my hand operated mill, never had a problem, always peck drill them. Usually I have the hole already drilled that I am doing the countersink for. I don't use a high RPM (mill can't even do high RPMs) and I go very slow, so you know what, this is probably easier to mess up on a CNC machine, because like I said, I do it all the time on my small mill, no problems.

    For countersinking on a CNC I'd use the 4 flute 1/4" bit I mentioned previously, and cut out the larger circle and I have done this before also many times with no problems.



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    Quote Originally Posted by NIC 77 View Post
    I countersink holes in aluminum all the time this way on my hand operated mill, never had a problem, always peck drill them. Usually I have the hole already drilled that I am doing the countersink for. I don't use a high RPM (mill can't even do high RPMs) and I go very slow, so you know what, this is probably easier to mess up on a CNC machine, because like I said, I do it all the time on my small mill, no problems.

    For countersinking on a CNC I'd use the 4 flute 1/4" bit I mentioned previously, and cut out the larger circle and I have done this before also many times with no problems.
    Technically it's counterboring... since a mill typically has a slower RPM, and slower (manual) operation, many flutes are used so that each cutting edge meets the specs for chipload and SFM. Typically on a router, higher speed spindles are used, so unless one sets the feedrate very high (which may violate the SFM rating of the tool), a single flute tool is used, thus allowing the correct chipload at the higher RPM.



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    Default Re: Cutting 1" thick aluminum on CNC

    Louie, chip load and feed have no effect on the SFM. The only variables are bit diameter and the RPM. Aluminum is good for 50-1000+ sfm as long as chip evac is there. On my manual mill at 1400rpm I still use a single flute countersink.
    A counter bore is a cyclinder pocket, usually concentric with a drilled hole. A counter sink is a drafted or angled wall

    Luthier/Woodworker/Machinist in NS, Canada.


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    Countersinking is a bit different if you have a predrilled hole.

    As for using a two flute end mill in solid aluminum im still of the opinion that they really dont like to be plunged into the material. At least that is my experoence with a limited number of two flute end mills that ive used. In a nut shell you can't feed them like a drill bit.

    As for the original poster it would be great to have more info. Im wondering if the cutter is loading up or maybe he just got a bad batch. Also im left a bit confused because it sounds like what he is trying to do is to put round holes in the plate something better done with drill bits. Sometimes with these posts what i think is being done or happening is completely different than what is actually going on. This could be the case here because originally i thought the problem was with cutting out some sort if shape out of that Aluminum.

    Quote Originally Posted by NIC 77 View Post
    I countersink holes in aluminum all the time this way on my hand operated mill, never had a problem, always peck drill them. Usually I have the hole already drilled that I am doing the countersink for. I don't use a high RPM (mill can't even do high RPMs) and I go very slow, so you know what, this is probably easier to mess up on a CNC machine, because like I said, I do it all the time on my small mill, no problems.

    For countersinking on a CNC I'd use the 4 flute 1/4" bit I mentioned previously, and cut out the larger circle and I have done this before also many times with no problems.




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    Quote Originally Posted by jahnj0584 View Post
    Louie, chip load and feed have no effect on the SFM. The only variables are bit diameter and the RPM. Aluminum is good for 50-1000+ sfm as long as chip evac is there. On my manual mill at 1400rpm I still use a single flute countersink.
    A counter bore is a cyclinder pocket, usually concentric with a drilled hole. A counter sink is a drafted or angled wall
    Yes, I know that. My point was that while a theoretical feedrate xan be calculated, it isn't necessarily acievable due to the manufacturer SFM rating. Just can't type as fast as my mind thinks with 2 thumbs and a 5" screen.....



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    Default Re: Cutting 1" thick aluminum on CNC

    Knowing that my CNC machine was designed to cut wood, I'd probably just peck a hole deep enough in the aluminum to be able to take the piece to my drill press...counter sink it and drill it out there. The thickest aluminum I've cut is 1/8" and I had no issues with a single flute bit. My feeds and speeds were very, very conservative.



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    Default Re: Cutting 1" thick aluminum on CNC

    Quote Originally Posted by wizard View Post
    Countersinking is a bit different if you have a predrilled hole.

    As for using a two flute end mill in solid aluminum im still of the opinion that they really dont like to be plunged into the material. At least that is my experoence with a limited number of two flute end mills that ive used. In a nut shell you can't feed them like a drill bit.

    As for the original poster it would be great to have more info. Im wondering if the cutter is loading up or maybe he just got a bad batch. Also im left a bit confused because it sounds like what he is trying to do is to put round holes in the plate something better done with drill bits. Sometimes with these posts what i think is being done or happening is completely different than what is actually going on. This could be the case here because originally i thought the problem was with cutting out some sort if shape out of that Aluminum.
    The bits had zero wear on them before using. They were brand new. The first bit broke very quickly while machining the profile, and not the plunge. The first bit made it through the plunge fine and broke after a minute of profiling while still in the profile. The second bit snapped same spot but on the instant it touched the material on the plunge. It wasn't even like the bit stalled for a second, not being able to plunge, it was like an instant snap the instant it made contact. I think this is due to it's long flute length, and not being designed for plunging. The fact I was able to finish the job with a much shorter bit without issue, and many of the same short single flute bits in the past, tells me that bit wasn't suited for my needs. It's probably intended to be used with very shallow cuts.

    I have decided to buy a 3/8" 2 flute HSS Onsrud bit since I can get them from a shop near home. I will use this for all the profiling. I have a 1/4" carbide spot drill I can use to mark out the through holes in the parts, and buy the required bits for drilling on the drill press. This was my method for all the steel in my machine, and works beautifully. I can use a 1/4" or 3/16" 2 flute short length bit for all the counterboring for screw heads. I may buy a 4 flute 1/4" for finishing passes, but I'll have to test the finish I get with the 3/8" cuter first.

    The thickest aluminum plate I've cut before this was 3/8" on a router, so I went into it thinking about machining everything in one go on the router, but the suggestions here point to spot drilling and finishing on a drill press or mill.



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    Default Re: Cutting 1" thick aluminum on CNC

    I have cut 30mm aluminum plate on my cnc wood router, using both a cheap chinese 6mm x 30mm long single flute solid carbide, and a home depot freud 2 flute spiral solid carbide bit with only a 1" cut depth.

    If this is a one off job and you don't need to maximize effeciency, just use a very small step down, like 0.050" and take like 0.001" per tooth, while babysitting to clear the chips.



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    Default Re: Cutting 1" thick aluminum on CNC

    You have indicated how the tools break but im still interested if there is any build up on the cutters? That could be an issue if you have rational feed rates and depth of cuts.

    Recalculating feed rates might be in order to avoid a possible mistake where you have the cutter overloaded.

    Speaking of feed rates, obviously you need to know the spindle speed fairly accurately. If you have one putting a tach on the spindle to verify RPMs to make sure you dont have RPMs grossly out of spec.



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    Default Re: Cutting 1" thick aluminum on CNC

    I guess the OP is cutting with too aggressive speed and feed, on my side I can cut / engrave aluminum all day without breaking a tool bit

    60mm thick cast aluminum with 1/8 carbide bit (manually sharpened single flute) three days of cutting aluminum thats the time it gets dull (resharpen and back again)

    Cutting 1" thick aluminum on CNC-20170228_104103-jpg

    Attached Thumbnails Attached Thumbnails Cutting 1" thick aluminum on CNC-20170228_104103-jpg  


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    Default Re: Cutting 1" thick aluminum on CNC

    There was no wear on any cutter. All brand new. No wear after the fact. Didn't cut long enough to get wear/build up. I'm 99% confident breaking these bits had to do with the length of the cutter and how I was plunging.

    KHOUJ - I was not cutting aggressively as I said in my post. I was cutting as conservative as possible. Also cast aluminum is a different material altogether. Could you please post your specs? What tool, speed, feed, DOC, length etc. It's great to know you aren't without issues. Could you let me know how?



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    Default Re: Cutting 1" thick aluminum on CNC

    Quote Originally Posted by Matthew_ View Post
    There was no wear on any cutter. All brand new. No wear after the fact. Didn't cut long enough to get wear/build up. I'm 99% confident breaking these bits had to do with the length of the cutter and how I was plunging. KHOUJ - I was not cutting aggressively as I said in my post. I was cutting as conservative as possible. Also cast aluminum is a different material altogether. Could you please post your specs? What tool, speed, feed, DOC, length etc. It's great to know you aren't without issues. Could you let me know how?
    Well then I guess the main issue on your tool bit snapping is your plunge speed, everytime a tool bit is plunged on the material you need to do it slowly, if you can program your CAM to do a 50mm/min on plunging then I guess you`re all right, you need also to research on your tool bit specifications, my machine specification is only a 6040 CNC router for wood, 1.5Kw watercooled spindle 24K RPM, my tool bit is just an ordinary carbide router bit 2 flute for wood, im quite good in manual machining (lathe, mill) so im familiar with the tool bit properties by just plunging it manually on the material itself, there`s no accurate data you can get when you cut metals (too many variables like strength of material,spindle speeds, etc,), the best way to do it is to manually plunge it and actually see where it`s limitations, that`s the time you can accurately find it`s optimum feeds and speeds, tool bit sharpening technique is also a factor, in my case im the one sharpening my bits or shaping it to my preference, I always run my spindle @ 24K rpm that`s why I need to alter the angle of the tip on my bit, too deep plunge will always snap the tool bit whether it`s a HSS or carbide, I like the carbide bits due to it`s toughness and will not easily get dull. I guess you can try manually controlling your CNC to find it`s optimum speed. to tell you the truth I can assemble an entire 1911 gun accurately piece by piece by just using a chinese wooden router and a wooden carbide tool bit (slides, lower receivers, trigger assembly)

    Cutting 1" thick aluminum on CNC-20161210_113448-jpg

    Cutting 1" thick aluminum on CNC-20161228_120941-jpg

    Attached Thumbnails Attached Thumbnails Cutting 1" thick aluminum on CNC-20161210_113448-jpg   Cutting 1" thick aluminum on CNC-20161228_120941-jpg  


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Cutting 1" thick aluminum on CNC
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