584,833 active members*
5,585 visitors online*
Register for free
Login
IndustryArena Forum > MetalWorking > MetalWork Discussion > Dry milling of aluminum
Page 1 of 2 12
Results 1 to 20 of 23
  1. #1
    Join Date
    Mar 2013
    Posts
    21

    Dry milling of aluminum

    Hi everyone. I would like to know if anyone has any suggestions, as far as CNC milling of aluminum without liquid lubricants or coolants.

    I am operating a Taig benchtop CNC mill in laboratory / cleanroom environment. Mostly I'm machining various plastics, and for these I've by now figured out how to choose types of endmills, feeds,speeds, depths of cut, and so forth, to reliably machine with high precision and excellent surface finish. (What I've discovered, with plastics at least, is that by far the most critical requirement is to prevent chips from being dragged back into the cut by the rotating endmill.)

    Occasionally I cut brass, steel, or even stainless on this machine, and I can get excellent results with these materials also, as long as I respect the limits of the machine and go about things in the right ways.

    All of the above, by the way, I can do without any liquid lubricants or coolants.

    With aluminum though, I almost always have troubles. The aluminum sticks to the flutes of the endmill in a way that I've not seen with any other material; this seems to be the basis of my troubles. I seem to get the best results with new, razor sharp HSS mills, though I've tried different forms of carbide as well as HSS with various coatings. Sometimes things work out okay and I will get a clean surface finish, though I don't completely understand why and this has been hard for me to predict. Other times I end up with little "scrubs" of material sort of mushed against the machined aluminum surface, no matter what I do.

    Now, I know there are many who will want to say to me: Use a lubricant! It only takes a little bit! You have to use a lubricant with aluminum! Try WD-40, or this, or that, just a few drops here or there!

    But thank you, I know all that. If I use lubricants, everything is okay, the endmill stays clean and shiny, and if I keep the chips out of the way then cuts come out beautiful and clean.

    However, what I'm often doing, is taking a piece of fixturing out of an ultra-clean vacuum chamber, and machining a little off here or there, then putting it right back into the chamber to try how something fits. I can take the part out of this room, over to a big and dirty mill next door, do the machining with flood coolant or whatever, then bring it back, clean it with alcohol, and acetone, then high-grade methanol, then half a day later I can be ready to put it back in the chamber; then maybe have to repeat all of that several times. Well this doesn't work, so for now I just suffer with frequently poor surface finishes, and using up a brand new endmill almost for every cut where I need dependable surface quality.

    I've thought of trying even to use wax as a lubricant, which can work, but still it leaves residues of wax on my parts, which later will liquify at elevated temperatures, so in the end it's really no better than oil anyway.

    Okay - any suggestions are most welcome!

    --dave

  2. #2
    Join Date
    Dec 2013
    Posts
    5717

    Re: Dry milling of aluminum

    You have an interesting problem. Given the conditions, maybe try distilled water? If you are using 6061 aluminum, it's pretty gummy and wants to weld to the end mill, 7075 aluminum might be more forgiving.

    EDIT:

    Another thought is to slow the spindle and feed speeds way down and just cut slower, that should help with the heat generated.

  3. #3
    Join Date
    Nov 2007
    Posts
    479

    Re: Dry milling of aluminum

    Quote Originally Posted by Jim Dawson View Post
    You have an interesting problem. Given the conditions, maybe try distilled water? If you are using 6061 aluminum, it's pretty gummy and wants to weld to the end mill, 7075 aluminum might be more forgiving.

    EDIT:

    Another thought is to slow the spindle and feed speeds way down and just cut slower, that should help with the heat generated.
    This with a cold gun air coolant system might be the answer. Control heat build up and improve tool life during dry machining using EXAIR's Cold Gun

  4. #4
    Join Date
    Dec 2013
    Posts
    5717

    Re: Dry milling of aluminum

    One more thought is to climb cut a light finishing pass. This removes the ''fuzz'' from the surface.

  5. #5
    Join Date
    Mar 2012
    Posts
    192

    Re: Dry milling of aluminum

    Use denatured alcohol or IPA as a cutting fluid. It will help keep the end mill cool and lubricate enough to mitigate chip welding. Then it should quickly evaporate and leave no residue.

  6. #6
    Join Date
    Sep 2011
    Posts
    261

    Re: Dry milling of aluminum

    My thoughts:
    1. High pressure air or a cold air gun on the tool (cold air guns are pretty worthless in my experience. Generally, I'll take 90PSI shop air blowing on the tool over a cold air gun)

    2. Have you tried ZrN coated tools? ZrN has one of the lowest coeffiecient of friction's and reduces chip sticking

    3. If you have a medium size budget to work with, use a CO2 system (like CoolClean systems) that injects CO2 into a high pressure air stream which then solidifies as it depressurizes and comes out of the tip as solid, cold CO2 at high velocity. This system works great, but it pricey.

    Overall, the most effective option is Co2, but that is expensive. 2nd to that, I would put a high pressure air gun RIGHT at the cutter tip or maybe even rig a steel brush on a Mag Base to brush the trailing side of the end mill (if space allows, like cutting an OD)
    CNC Product Manager / Training Consultant

  7. #7
    Join Date
    May 2014
    Posts
    23

    Re: Dry milling of aluminum

    Sounds like a low grade aluminum, like said earlier I'd make sure always to be using 7075 aircraft grade aluminum....should make a difference....or at lease 6061.

    And because you have no coolant......you'll be limited to speeds and feeds and depths of cuts..........just take lighter cuts until your desired finish is achieved....and light clean up passes.

    Or just leave and use the big mill to get what you want and get yourself an ultrasonic bath and clean the parts in a 10-20 mins after and bring back into the clean room clean.......seems this would be the most efficient way cause you won't have to machine really slow.

    Machining in a clean room eh......hmmmm.

  8. #8
    Join Date
    Jun 2010
    Posts
    4252

    Re: Dry milling of aluminum

    Aluminium sticking to the cutter - it's well known and called Built Up Edge or BUE. The softer the grade, the worse the problem. 7000 series and casting alloys are much much better. But if you are machining existing equipment you may not have a choice. Do not use a TiAlN coating: that sticks WORSE. TiN is OK.

    Alcohol is quite commonly used for machining aluminium, but you need an exhaust fan ducted right outside, or you may end up with a high blood alcohol content and get booked when driving home. Not me, but one of my staff! Kero might be a substitute.

    One solution which I don't think has been mentioned is a dripper bottle of clean alcohol plus a vacuum nozzle with an outside exhaust. A shop vac is fine with a rough shaped nozzle.

    Cheers
    Roger

  9. #9
    Join Date
    Mar 2013
    Posts
    21

    Re: Dry milling of aluminum

    Okay everybody, first of all thanks for all the replies. Some interesting ideas to try, that I had not thought of before.

    By the way: Does anybody have comments or suggestions regarding carbide versus HSS cutters for aluminum. My experience has been, that a brand new, uncoated, good quality HSS endmill, new and unused and razor sharp, seems always to work best for aluminum. But they don't last very long. Especially taking many light and shallow cuts, when it's only the very tip that's doing any cutting. The business end of it seems to wear out really fast, even during the cutting of a single part. So either I end up going through a lot of them, or looking at carbide. I've seen a lot of different kinds of carbide endmills, but none I've ever found seem to be ground as sharp as HSS, or with the same sort of rake or clearances that seem to work for aluminum.

    --dave

  10. #10
    Join Date
    Dec 2013
    Posts
    5717

    Re: Dry milling of aluminum

    For light cutting I like solid carbide wood router bits, cheap and available at your local hardware store. Razor sharp and seem to last a long time, hours of cutting in aluminum with a cutting oil/coolant, maybe less with no coolant. Aluminum is pretty abrasive. They have a geometry that is pretty good for soft materials.

  11. #11
    Join Date
    Jun 2010
    Posts
    4252

    Re: Dry milling of aluminum

    You can get some wicked sharp HSS cutters for aluminium. They are OK for plastics too. Just don't touch steel with them as that will detroy the edge.
    Coating - needs to be really thin or it rounds the edge.

    Now the problem with machining aluminium is that you can get tiny particles of aluminium oxide embedded in the bulk. Guess what: that is AlOx, what you have in a grinding wheel. So while aluminium cuts very nicely, it can still be rather abrasive. Just how abrasive depends on the mill and probably even the batch.

    You can get good carbide cutters for aluminium, but they will be 'not cheap'. Chinese and Taiwanese carbide won't take such an edge, but German and Swedish carbide will. However, the latter two may be 3 times the price of the Asian stuff. In a production environment, you go for the Euro stuff!

    Cheers
    Roger

  12. #12
    Join Date
    Jun 2007
    Posts
    3891

    Re: Dry milling of aluminum

    flood coolant.

    /me runs.

    :P

    alcohol would be the best, in terms of actually being a coolant (and a really good one at that) and leaving behind a dry work peice. ive hooked up a pop bottle with a clear plastic tube and a "clamp" to regulate the flow to about 1 drop ever few seconds. its all you need. you can also mist it. drawback is fumes. you need some venting if you are going to run this for a long time. dont use methanol in a mister though, cause the fumes are bad in the non recoverable brain injury kinda way.

    for totally dry, on that type of machine... just slow the spindle waaaaaaaaaaaay down. like under 100sfm. the chips weld to the tool because they are heating up and fusing. running super slow will generate minimal heat. if its shallow surfacing and edging this should be fine. drawback is of course sloooow throughput, but it sounds like speed isnt your primary concern.

  13. #13
    Join Date
    May 2015
    Posts
    1422

    Re: Dry milling of aluminum

    I'm a big fan of a 20/80 ethanol in water coolant mist on aluminium, as I believe is used by the Datron machines. Cuts nice and clean, no oil leftovers and dries off the machine and workpiece with a clean airblast usually. I also like that I can let the machine dry off and then vacuum up the swarf - none of that sticky residue hanging onto things! WD-40 works well but leaves a mess.

    I've tried a bunch of things and cutters and honestly, could not get dry aluminium cutting to play nicely. It almost always ended up in a BUE followed by a snapped cutter.

    HSS vs carbide: our workshop had a job making electronic enclosures with radiator fins out of billet 6061 T6. The fins were a bear. Thin channels between fins meant a long, skinny endmill for the cutting. Our very experienced machinist (old school Bridgeport guy, no CAM just programmed it in on the machine from a drawing) has been a fan of HSS forever but this job had him changing cutters twice per enclosure. Yeah, you can buy 10 cheap eBay cutters for the price of one half decent carbide equivalent. But that carbide equivalent was doing 10 cases before it died. He's now switching his tooling over to carbide as each old HSS cutter wears out. I've learned from this and I'm doing the same now: I'm not buying super expensive stuff but I am getting carbide whenever I can and, especially on small mills with high RPM spindles, it makes a huge difference.

  14. #14
    Join Date
    Dec 2007
    Posts
    2134

    Re: Dry milling of aluminum

    I had a lot of pre-mature wear of solid carbide end mills dry machining because it was turning very gummy during machining and re-cutting constantly as a result, causing a lot of drag. Squirts of lube made a huge difference I found.

    cheers, Ian
    It's rumoured that everytime someone buys a TB6560 based board, an engineer cries!

  15. #15
    Join Date
    Mar 2013
    Posts
    21

    Re: <<<Almost?>>> dry milling of aluminum

    Quote Originally Posted by ihavenofish View Post
    alcohol ... about 1 drop ever few seconds.
    Hmmm... Okay, so... can this really be true??? If so, then the truth is I need to let go of my fanatical pursuit of trying to cut dry...

    When I've read about people using alcohol as a milling coolant before, I've just assumed it must have to be a heavy and continuous stream of it to really work, running all over everywhere, a fire hazard in addition to much nuisance. But, for sure I can tolerate dripping isopropyl alcohol at a rate of a drop every few seconds; I can even use anhydrous IPA that's cheap, and will air dry, and not even leave any water as residue in my machine. I guess it would be like a dream come true, if alcohol can really work as a cutting fluid / coolant when run at that rate.

    Quote Originally Posted by RCaffin View Post
    You can get good carbide cutters for aluminium, but they will be 'not cheap'.
    Could you suggest some sources of "good carbide cutters for aluminum". Mostly I just get whatever McMaster has, since they are so incredibly easy to deal with, and everything in their warehouse I can get here next day just via ground shipping. Though I do buy also from MCM, where sometimes certain things are a lot cheaper; also from Harvey Tool, which makes certain very nice unusual cutter forms in very small sizes, which I use a lot here.

    --dave

  16. #16
    Join Date
    Jun 2010
    Posts
    4252

    Re: Dry milling of aluminum

    Harvey Tool ... on a par, some might say, with cheap Chinese. McM - a little better, but not serious production engineering stuff.
    Get one of the trade mags like Cutting Tool Engineering and read through. Or go for a Google for a while.
    Iscar, Kennametal, YG, Cobra, Kyocera (very nice), Sandvik, OSG, ITI, Horn, Microcut ... There's a stack of them out there. USA, Europe, Japan, but not China and care with Taiwan.
    Buy brand name stuff rather than cheap distributor.

    Cheers
    Roger

  17. #17
    Join Date
    Apr 2003
    Posts
    540

    Re: Dry milling of aluminum

    I use Beolube in the push stick form. It works great but it still liquefies at high temp and then will leave contaminants and residue. You didn't really explain what specific end mill types you have tried but I know using the right cutter for the material and using appropriate/specific speeds & speeds will with have a huge impact on cut quality. I have a number of high helix end mills specifically for aluminum and they definitely make a difference. I'm sure most of the major bit makers have a engineer available by phone for helping with such issues and can offer expert advice on their specific end mills.

  18. #18
    Join Date
    May 2015
    Posts
    1422

    Re: Dry milling of aluminum

    Don't use pure IPA etc, massive fire hazard in a mill. Use it diluted and mist it with one or two cheap locline type misters.

  19. #19
    Join Date
    Jun 2007
    Posts
    3891

    Re: <<<Almost?>>> dry milling of aluminum

    Quote Originally Posted by mosaicdave View Post
    Hmmm... Okay, so... can this really be true??? If so, then the truth is I need to let go of my fanatical pursuit of trying to cut dry...

    When I've read about people using alcohol as a milling coolant before, I've just assumed it must have to be a heavy and continuous stream of it to really work, running all over everywhere, a fire hazard in addition to much nuisance. But, for sure I can tolerate dripping isopropyl alcohol at a rate of a drop every few seconds; I can even use anhydrous IPA that's cheap, and will air dry, and not even leave any water as residue in my machine. I guess it would be like a dream come true, if alcohol can really work as a cutting fluid / coolant when run at that rate.



    Could you suggest some sources of "good carbide cutters for aluminum". Mostly I just get whatever McMaster has, since they are so incredibly easy to deal with, and everything in their warehouse I can get here next day just via ground shipping. Though I do buy also from MCM, where sometimes certain things are a lot cheaper; also from Harvey Tool, which makes certain very nice unusual cutter forms in very small sizes, which I use a lot here.

    --dave
    not isopropyl, that is too aggressive in that it can dissolve all sorts of seals and plastic parts of your machine. when i do it, i uses methyl hydrate (methyl alcohol). the reason it works is because it evapourates near instantly cooling the aluminium and thus not letting it stick to the tool.

    ethyl alcohol is a safer choice than methyl, both for machine seals, and since methyl hydrate can be toxic if inhaled in large amounts (as with other things beginning with meth :P).

    look at datron on youtube for examples of high performance mist systems (you can buy these under a hundred dollars from noga and others), but for your little machine which isnt super fast or powerful, the dropper should be cheap and easy.

  20. #20
    Join Date
    Dec 2009
    Posts
    166

    Re: Dry milling of aluminum

    These are HSS end mills off Ebay they work pretty good with these feeds I use Plain water flood cooling
    the ally is marine grade 5083 similar to to 6061 a real pain to mill .

    Chinese VFD Spindle
    you need to keep your plunge rate down real low F50-F100 make sure you have lead in not plunge

    Full width cut i.e slot

    6mm HSS 4 Flte F160 Sp4456 Doc 3mm Stock to leave 1.5mm
    5mm HSS 4 Flte F160 Sp5250 Doc 3mm Stock to leave 1.5mm

Page 1 of 2 12

Similar Threads

  1. Replies: 11
    Last Post: 01-13-2016, 05:09 AM
  2. RFQ - Milling Aluminum
    By universalfab in forum North America RFQ's
    Replies: 6
    Last Post: 02-06-2014, 02:11 AM
  3. Aluminum milling job
    By zmaker in forum Employment Opportunity
    Replies: 10
    Last Post: 12-29-2009, 03:59 PM
  4. Milling aluminum
    By cliffaddy in forum Taig Mills / Lathes
    Replies: 3
    Last Post: 12-10-2008, 05:24 PM
  5. RFQ - Aluminum Milling
    By Axiom in forum Employment Opportunity
    Replies: 15
    Last Post: 03-06-2007, 05:29 AM

Tags for this Thread

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •