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Thread: Can't figure out how to mill aluminum

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    Can't figure out how to mill aluminum

    Hi,

    I finally got around to CNC'ing my HF Micro Mill #47158!

    Just curious what depth and ipm others are using for aluminum on these micro mills(or mills where RPM max is limited to about 2000rpm)?

    So far...I've got a couple of passes on aluminum that have burr all over the path and made 3 sets of broken HSS 1/16" 2 flute micro end mills. Not looking forward to making any more of either these. ;-)

    The flat bar of aluminum was from Home Depot but am not familiar with the different types of metal to tell what I got. It's the flat aluminum that comes in 1/8" x 1" x 3FT.

    I need to keep records of my trials but I believe i was running:
    - between .5 and 1 ipm @ 2000RPM, depth around 0.010"
    - and another time with 5-6 ipm @ 2000RPM, depth around .005"
    Hate to go any slower since my controllers get HOT the crawling 1ipm speed.

    Thanks in advanced for your comments,

    Dang


    To add, I was able to make a clean letter engraving on another unknown piece of aluminum(different), but again I had to go around .5-.7 IPM.
    This piece of aluminum felt like chrome/plastic more than metallic aluminum, but the freshly milled faces clearly shows that it's metallic.

    Similar Threads:
    Attached Thumbnails Attached Thumbnails -img_6449_small-jpg   -img_6450_small-jpg   -img_6451_small-jpg  


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    The first question that comes to midnd is where did the end mills come from? Are they actually end mills or engraving bits? Second are you milling with the drill or are you using a set of collets? End mills often slip in drill attachements. Another possiblity is that your quill is drifting to deep during the cut.

    I cut with small enco 2 flute 1/8 and 1/16 and run at 1750 at 6 to 7 ipm and a depth of at least .025 with out any problems.

    I don't give a damn if you don't like me, cause i don't like you cause you are not like me.


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    My first thoughts looking at your attached pictures.
    1. The first picture looks exactly like my first cuts with NO coolant!
    2. Like the poster above, are you putting the end mill in the drill chuck? They are not made to take side loads and can even fall off. (don't ask how I know).
    3. How much backlash do you have in your system. when taking cuts like the one in the first photo will give a combination of conventional and climb milling. When climb milling, the cutter can grab and the result is a broken mill-especially in a small cutter such as a 1/16

    Art
    AKA Country Bubba (Older Than Dirt)


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    as was stated above,

    1. use a good quality end mill. it should cost around $15-30 each.
    2. use 2 flute for aluminum as the heat from cutting can bind up chips in the higher flute end mills.
    3. use coolant. (WD-40 in a spray bottle works pretty well) unless you want to pony up the money for a mist system or a flood system with enclosure.
    4. those tiny end mills need alot of speed, so cranks her up.
    5. home depot aluminum is not good to cut. i think its actually a 300 series and is gummy. get yourself a peice of 6061, that is pretty machineable. once you get the hang of that then move onto other materials.
    6. also i would use an 1/8" end mill. they are a little more common sometime cheaper.



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    Thanks Legion99999 & Bubba,

    Given your comments, there are a few things I will have to figure out.

    I guess what I wanted to hear was if others had success milling through aluminum at these slower speeds <2k rpm with smaller bit sizes < 1/4".


    To answer the questions:

    1) The use of collets and verifying backlashes
    I'm guilty of using the chuck. It seems very sturdy and there are no signs of slippage/scoring on the shank.

    I've not yet got the tools, like the dial indicator, to tell how much play I really have in the chuck and table backlash, but by hand there is no play laterally or vertically on the chuck. The table in the y axis does has a "tiny" amount of play which I am having trouble working out w/o binding the table.

    I'll have to get a set of collets and measuring tools within the next few months.


    2) Coolant use.
    Blessed my wife, I have the machine in our office :-) So spraying liquids is out of the question...at least for now. Too scared to work in the basement at night...lol

    If you're wondering how I deal with the chips; I've been standing impatiently with a vacuum throughout the entire process...not fun. but the fun of looking at the cnc in action totally offsets it.


    3) End mill types.
    2 of the 3 bits were "un-named brands" which I got from a local surplus store(ax-man). They are 2 fluted 1/16" bits with the plastic ring in the middle of the shank...I believe they're for jewelers. They definitely looked like milling endmills. I used these to mill out my daughters name "LILY" on the second piece of aluminum.

    The 3rd bit I broke was a double ended 2 flute 1/16" HSS made in USA which I broke both ends.(used on both the burred up parts) I got this bit at the Tried and True store in MN. They're not new, but the tips were original and very sharp. Unfortuantely I don't take very good notes and didn't jot down the other markings on the bits.


    Thanks,

    Dang



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    Runner4404spd,

    YIKES $15-30. I guess I've been going REALLY cheap. The bits I got were around $3-$5 from a used machine shop called Tried and True. I did hear that the Chinese bits were no good so aside from the bits from a surplus store, I've been sticking with USA brand.

    I've not thought about WD-40, but I'll have to hold off if possible until summer when I can move the machine to the garage.

    Thanks for the tip about the Home Depot aluminum. I figure it may have something to do with that. since my other unknown aluminum piece milled very well, although at too slow of a speed.

    The inspiration for me getting into the whole CNC thing is my interest in r/c helis. I do have a 1/8" end mill I could use, but the micro heli parts are SOOOO small that I must use 1/16" or smaller....



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    Dragon-dude,

    Sorry I didn't answer your question directly concerning speeds etc.
    I routinely mill on my mill drill using 1/4" at speeds of 3500 (I have modified it to go that high) but before, would do it at 2500 in aluminum. Steel is on the order of 1400 and I use flood coolant.
    As for the mills I "normally" use, in contrast to the above are the "cheap" ones from enco. They can be had for approximately the same price as you are paying for used ones! Until I can become proficient, I would rather break the cheap ones rather than the expensive ones:})
    On the other hand, last week I had a solid carbide .070" one that I was milling .065 deep in aluminum tooling plate and it lasted 5 hours before I (did something stupid) and broke it.


    With regards to
    "1) The use of collets and verifying backlashes
    I'm guilty of using the chuck. It seems very sturdy and there are no signs of slippage/scoring on the shank. "
    The problem lies more with the fact the chuck is held on by means of a taper and after a period of time, vibration will cause the chuck to "fall off" the taper.

    Hope this helps, and hang in there. We all have to learn somehow. I also find what works for me may not apply to you and vise/versa:})

    Art
    AKA Country Bubba (Older Than Dirt)


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    Bubba,

    You're right it's steep learning curve. Both terminology and expertise.

    Don't worry about not chiming in your feeds and speeds initially, I posed more questions than I thought I had :-)

    This last couple weeks have been somewhat discouraging, but the posts here and machining videos on youtube helps re-encourages me. I'll keep playing around with fine tuning my electrical equipment until the collets and dials get ordered for a real re-adjustment of the machine.

    The "cheap" bits have worked for you for some time? Sounds like you use coolant every single time you machine metals?

    I may be wrong, but I think the drawbar on this machine holds up the chuck. I've never taken it apart but that's what the exploded diagram seems to show.



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    dragon_dude
    I have used the cheap ones most of the time. Can't claim originality for that one as I saw it in one of the tips on the original IH web site.
    As for the coolant, I started out like you and got the same results. Then with the help of a mentor and reading posts here and elsewhere, found that coolant was the "secret" in helping get nice cuts. It not only keeps the tool cool, it flushes away the chips and the latter I think is probably more important than the cooling! I have had times when I wasn't "flooding" enough and I could hear the chips being "recut" and could see the result.

    As for the drawbar, yes, that is what holds it up in the quill, but all of the ones I am familiar with are adapters for the quill taper (R8 or Morse) to the chuch taper (usually Jacobs).

    I also have found that I have to take the "recommended" feeds and speeds with a grain of salt for MY MACHINE. If I follow the recommended ones, my machine is not rigid enough to be able to handle them. Yeh, I know the production guys will chime in and say that I will prematurely wear out my tools. Yep, sure will, but they last longer than the ones I break because I followed the standard recommendations! The biggest thing I have learned is that because cnc will repeat so nicely, that I need to make many shallow depth of cuts faster rather than fewer deep cuts. For instance, when making the slots for my vacuum chuch recently (the .070" dia carbide end mill), I was running it at ~50,000 rpm with a doc (depth of cut) of .06" at a speed of about 8IPM. It made dust for chips, but other than my stupid act that broke the one 5 hours into the job, it lasted. Previously if I tried a cut like that with say a doc of .030 and a speed of say 5IPM, I would break the mill in oh about 5 inches of cut!
    This is another reason for most of my work, I use the "inexpensive" tools. I am still learning the capabilites of my machine and would rather break a $3 mill than a $15-$30 one. In a few years when I learn how to do it properly and what my machine can do, I may graduate to a better class of tool (or machine:})

    Art
    AKA Country Bubba (Older Than Dirt)


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    if your cutting inside and can t use oils then , i'd suggest using a spray bottle with soap or straight water .there is no doubt your melting the aluminum rather than cutting it ,water should keep it cool enough not to melt .quite often when i setup an aluminum job i will run most of it dry , it can be done with caution, i have a good idea of where and when my meltdown points are and i judge it within those boundaries . after youve done a number of cuts it will become second nature , you'll have control over the machine rather than it having control of you
    at home on my router table i use wd40 or 3 in 1 oil ,but they smoke at 20000 rpm ,
    it may be worth trying the 3 in 1 oil , it doesn t stink and i doubt it will smoke at the 2500 rpm that you are running http://en.wikipedia.org/wiki/3-In-One_Oil



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    Ditto what Runner440 said. Your material is most likely 3003 or 6063, neither of which will machine very well with your setup. Pickup some 6061..

    Something else which has been touched on is the use of a drill chuck for milling. I've seen some of those chucks have 0.002" runout, which effectively turns your 2-flute cutter into a wobbly 1-flute cutter...



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    Nice Z support gas springs! By any chance do you have a part list, I've been waiting to install them for some time now ? I'm just about to take the plunge on a new mill and for fun I'm beefing up this machine until I get the other.






    There could be a combination of things that you might not have correct, here goes....



    "The flat bar of aluminum was from Home Depot but am not familiar with the different types of metal to tell what I got. It's the flat aluminum that comes in 1/8" x 1" x 3FT."


    Aluminum likes to stick to the cutter when reaching hotter temperatures (caused by fiction, meaning too much speed and not enough feed or vise versa) and will cause the burr in your project (this is what I think your main problem is, if you're using brand new sharp end mills).

    I'd look into using WD40 for a lube and a shop vac to remove the debris. The aluminum you bought is very soft, so you would need to make sure your feed and rpm's are just right. LMS has a feed, rpm, etc.. calculator, I'd try it out and look into buying the Machinery handbook. You want to look for a consistent chipping, not something that sounds/looks like a chainsaw.


    Your depth of cut is kind of deep for this machine (especially without using collets), take shallower passes.

    You also have to watch your speed & feed and check your chip load. If you're planning to cut deep pockets, profile, etc.. I would look into making the motor mounts out of aluminum or maybe even dip them in some sort of concrete to stiffen them (just an idea, not sure if it would work).

    Another thing is to work out the play in your gibs and check your backlash screws on your lead nut (test with an indicator afterward). I just had the same problem with mine, which also lead to other problems that I didn't even know of. The vibration will rattle things lose, and with this machine you need to constantly maintain every little nut and bolt.


    What direction was your cutter rotating ( Forward I hope ) ?



    "Hate to go any slower since my controllers get HOT the crawling 1ipm speed."


    This is normal, mine get red hot.


    Feel free to PM me if you need more getting started help.



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