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.
Re: Dry milling of aluminum
Quote:
Originally Posted by
Jim Dawson
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
Re: Dry milling of aluminum
One more thought is to climb cut a light finishing pass. This removes the ''fuzz'' from the surface.
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.
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)
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.
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
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
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.
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
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.
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.
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
Re: <<<Almost?>>> dry milling of aluminum
Quote:
Originally Posted by
ihavenofish
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
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
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
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.
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.
Re: <<<Almost?>>> dry milling of aluminum
Quote:
Originally Posted by
mosaicdave
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.
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