CamBam
News:
 
*
Welcome, Guest. Please login or register.
Did you miss your activation email?
August 22, 2017, 07:53:51 am


Login with username, password and session length


Pages: [1] 2
  Print  
Author Topic: Do you use coolant to cut aluminium?  (Read 275 times)
Millone
Droid
**
Offline Offline

Posts: 76



View Profile
« on: August 13, 2017, 09:25:58 am »

Hi there,

time to time I need to cut some aluminium. My cutting strategy for profiling is 2000 mm/min 0.6 mm at time. I use a single flute 6 mm carbide at 18000 RPM, standard coolant liquid. This strategy normally does not break the tool and the result is quite good.

<a href="https://www.youtube.com/watch?v=5oWWBfGEa6c" target="_blank">https://www.youtube.com/watch?v=5oWWBfGEa6c</a>

The question is "do I really need the coolant or the air to clean out the chips is enough"?
I have tried with and without the coolant but always with air, the result looks the same. I would prefer not to use the coolant because it would be easier to clean up.
What do you normally do when you cut aluminium? Do you use the coolant?

Thanks
Felice
Logged

"It doesn't matter whether you're the lion or a gazelle-when the sun comes up, you'd better be running.

Dan Montano
dwc
Wookie
****
Offline Offline

Posts: 486



View Profile WWW
« Reply #1 on: August 13, 2017, 09:56:39 am »

If you are getting good results why change ?
When cutting Alu I always use a bit of WD40 because otherwise the chips tend to stick to the cutter.
But if you are getting good results with no problems I see no reason to change.
Don
Logged

Millone
Droid
**
Offline Offline

Posts: 76



View Profile
« Reply #2 on: August 13, 2017, 10:02:50 am »

Hi Don,
I am trying to understand other people experience on this topic. I am using the coolant but I noted in a couple of occasions, when the coolant bottle was empty, that there was no problem to finish the cut without coolant. May be I was lucky?
Logged

"It doesn't matter whether you're the lion or a gazelle-when the sun comes up, you'd better be running.

Dan Montano
dave benson
CNC Jedi
*****
Offline Offline

Posts: 768


View Profile
« Reply #3 on: August 13, 2017, 13:17:16 pm »

HI Felice

I mill quite a bit of al in sheet form 3,6,10,12 and 16 mm occasionally, I don't use a high speed spindle so i can't really comment on the correct speeds and feeds for you machine, but I always use a  sharp  HSS cutter and when it dulls somewhat I then use it to cut steel.

In the deeper materials where it's harder to evacuate the chips I drill large diameter holes that intersect the cut so that the chips are pushed out as the cutter go's by hole. If this is not possible then I add a bit to the cutwidth so the chips are not dragged into the cut.
 
Al comes in many grades 1050 (extrusions and such) machine poorly while 6061 machines much better. It's good to use a roughing and finishing mop and as others have mentioned a finish cut using climb milling can help.

I hardly ever use flood coolant but when I have to (extrusions usually which are pretty gummy and want to stick to cutter) I've used Wd 40 or the like and in a pinch I've used Diesel or Kerosene which worked but I don't recommend.

Dave 
 
Logged
kvom
CNC Jedi
*****
Offline Offline

Posts: 1367


View Profile
« Reply #4 on: August 13, 2017, 14:00:58 pm »

I use air blast, typically with larger 2-flute tool and deeper depth.  My mill's max RPM is 4000, so feed rates are less.
Logged
Bob La Londe
CNC Jedi
*****
Offline Offline

Posts: 2845


^ 8.5 pounds on my own hand poured bait.


View Profile WWW
« Reply #5 on: August 13, 2017, 16:22:56 pm »

I do a LOT of milling in 6061-T6.  I use bright (uncoated) carbide endmills, and I can push them quite a long time with flood coolant.  I tried a number of coolants/lubricants including air and even vortex chilled air.  

I used WD40 like a lot of folks to start out with.  It works ok, as a light spot cutting oil, but its not all that cheap and doesn't work as good compared to good light cutting oils like Tap-Magic or heavier cutting oils like Rapid-Tap.  Since my CNC machines will run continuously for hours I found spot lubricants didn't really work well for me.  I can't just stand there for hours squirting coolant/lubricant on the work piece.  

I tried dry.  Lots of machinist will tell you, "I cut aluminum dry.  Just use sharp cutters." but I suspect most of them are turning hand wheels or doing very short jobs.  Maybe some have the magic touch and they really are superior to the rest of us subhuman scum.  I think its more likely they are doing slow manual milling and they just stop before a mill gets to bad.  For me dry cutting resulted in chip welding, tearing, broken cutters and ruined work pieces.  

Air was a little better in that chips are blown clear, but it takes a lot of air.  I still use air when using down cutting mills in wood for finish work.  Its the only way to get the chips out of the hole.  I still wound up with all the same issues as plain dry cutting.  I run long jobs, and changing mills every few minutes to keep them sharp isn't an option.  I got less life out of HSS than carbide.  Vortex chilled air made a little difference, but not much.  It uses about 6 times as much air, because most of it dumps out the side of your vortex generator.  

One of the nicest materials I ever used was transmission fluid.  When I was starting to learn about high speed milling aluminum and I was still making molds on my little Taig 2019 I actually set it up to run flood transmission fluid.  I bought it in five gallon buckets and used a Little Giant pump and tub and just dumped it right on the work piece at the cutter.  I got great surface finishes, very long tool life, and believe it or not, no staining of the work piece.  The problems were I had to wash the work pieces with soap and water no matter the application, my work shop smell like a busy transmission shop, and the transmission oil burns at the cutting surface just like other cutting oil.  Because its was flooded over itself and kept cool it didn't burn bad, but I consumed transmission fluid at pretty high rate for one little machine.  Not as fast as I go thru water based coolant, but it was significant.  If you want a light spot cutting lubricant that's retail then transmission fluid is far superior to WD40.  I think Jeff Birt (Soigeneris) turned me onto transmission fluid.  

Then I tried Koolmist.  Oh, what a crap product.  It does ok for cutting finish, but I think pure water would do as well.  As a mist I hated the constant smell in the air, and it left my parts stained.  When I tried flood it was better, but it left my aluminum parts badly stained from yellow to brown.  I ran it only with distilled water and Kool mist (the company) still tried to tell me the problem was my water.  I know some guys use misters that have very little vapor, and if Koolmist in a sprayer had worked better I might have tried to build some, but it just wasn't that good.  I have seen other mist applications work very well, but some of them are pretty exotic. I didn't care for it and I had to run a pretty high volume to get passable results. 

For me I decided to find a good flood solution that moves the chips out and keeps everything cool.  On Lloyd's recommendation I decided to try Master Chemical Trim SC520.  It works every bit as good as transmission fluid, and doesn't leave my shop smelling like burned up transmissions.  I could get by with just rinsing the parts, but I do still wash them before shipping to customers.  The surface finish is good.  The tool life is fantastic.  There is no staining of any kind.  Lloyd tells me he just uses the same mix as in his machine for a brush on lube when turning on the lathe or doing other manual work.  I have to admit I still use oils at the lathe.  I mix it at about 6% with distilled water, and when I add more water (couple gallons per day per machine) I only add 4% about every other time I add water.  I used to try to be precise with the mix ratios, but I found as long as I could see the color of the SC520 at all the coolant mix worked great.  There is a very slight amine smell I noticed when I first started using it, but it didn't take long until I didn't notice it anymore.  My only real issue is keeping a good supply of water on hand.  I run two machines every day with a constant flood blast of the stuff.  Two more machines gets used a couple days per week with it.  I like it.  The next biggest issue is containment.  If you are running flood coolant you will want good enclosures with overlapping pieces at the doors and service panels or you will wind up with wet floors.  

I felt that every other solution I tried before just going to flood coolant was an amateur stop gap measure.  A sort of "get me by for now," temporary solution.  

Yes I am aware of big players on the high precision end like Datron who use a mist system.  I found I just wasn't happy with it.  

I use a single cutter for hours at 18000 to 24000 rpm and feed rates from 6 to 110ipm range.  My cutters tend to range from 0.026" to .25" at high speeds, and on the big machine I run cutters up to 3".  I just put the flood on it and let it go.  You get a good flood setup with a good enclosure and then the next thing to do is chip management.  Not the big stuff that stops at the filter screen, but the fine stuff that will circulate thru your system if you let it.  I found the first thing is to keep my tanks full.  If I do that one thing my chip problem is reduced by 90%.  Next is allow the tanks to settle for atleast 30 minutes after filling them.  I am working on a staged tank system with a settling tank on the machines and a second tank on the floor behind for the pumps, but I have not finished that yet.  

Can dry cutting work?  Yes, but not well.  I would not recommend it for long jobs at all.  Not at all for high speed. 

Does air blast work?  Yes, better than just dry anyway.  

Does, spot oil work?  Yes, very well, but its tedious.

Does mist cutting work?  Yes, but it can be finicky and your choice of mist is important as is the design of your misters.  

Does flood work?  Yes.  It works very well, but its a brute force approach that requires some brute force solutions.  A really good flood system can be a lot of work to design and setup, but a basic flood system can be as easy as a nozzle, some hose, a bucket, and a swamp cooler pump.  A proper coolant pump with a much longer shaft is MUCH better, but you can buy a swamp cooler pump at your local hardware store for less than $20.  

Am I real life long machinist or a laboratory researcher with all kinds of statistical evidence to back up what I say.  No.  Just my personal experience.  I tried a lot of things, and found the brute force fire hose approach work best for me.  
« Last Edit: August 13, 2017, 16:33:19 pm by Bob La Londe » Logged

Getting started on CNC?  In or passing through my area?
If I have the time I'll be glad to show you a little in my shop. 

Some Stuff I Make with CamBam
http://www.CNCMOLDS.com
Bob La Londe
CNC Jedi
*****
Offline Offline

Posts: 2845


^ 8.5 pounds on my own hand poured bait.


View Profile WWW
« Reply #6 on: August 13, 2017, 16:37:21 pm »

I would note I also machine some 5052 which is gummy and does not machine as well as 6061, and the same cutters and the same coolant setup works just fine.

If you want a really sweet aluminum to machine then try 7075.  Its as corrosion resistant as 5052, machines easier than 6061, and it is as strong as some steels.  They use it for AR15 receivers and some 1911 receivers.  It has two problems.  Its not easily welded and its more expensive. 
Logged

Getting started on CNC?  In or passing through my area?
If I have the time I'll be glad to show you a little in my shop. 

Some Stuff I Make with CamBam
http://www.CNCMOLDS.com
Bubba
CNC Jedi
*****
Offline Offline

Posts: 2202



View Profile
« Reply #7 on: August 13, 2017, 16:40:34 pm »

It always helps if the material to be machined is known..  Grin

Here what I go by, harder the material, it machine better that goes for steel, aluminium, etc..

Extruded aluminium or 0-T Condition (hardeness) - any coolant/lubricant a must
  
T-3 aluminium - coolant/lubricant recommended

T-6 aluminium - coolant/lubricant or compressed air not nesesarry, but it helps

T-7 aluminium - all of the above or none at all   Grin
Logged
Bubba
CNC Jedi
*****
Offline Offline

Posts: 2202



View Profile
« Reply #8 on: August 13, 2017, 16:47:43 pm »

Having working in aircraft industry I can tell you the only allowed aluminum for structural welding is 2023 (in only some cases) and 6061 (it is allowed by FAA, and to be welded by someone with FAA certification), 7075 is no-no,Period, It becomes brittle and it cracks. Wink    
Logged
Garyhlucas
CNC Jedi
*****
Offline Offline

Posts: 961


View Profile
« Reply #9 on: August 13, 2017, 17:13:56 pm »

I've used flood coolant and it definity works the best and gets the chips out of the cut best as well. If you want to keep the concentration in the right range you want a refractometer, no guessing. The biggest problem with flood is you really have to use it constantly. Lots of problems with bacteria, sludge and smell if you don't.

 I've used mist cooling and the mist in the air is nasty, can't be good for your lungs.  However a mist buster droplet style mister works really good for me. Much better than regular mist, almost as good as flood with very little mess.
Logged

Gary H. Lucas

Have you read my blog?
 http://a-little-business.blogspot.com/
Bob La Londe
CNC Jedi
*****
Offline Offline

Posts: 2845


^ 8.5 pounds on my own hand poured bait.


View Profile WWW
« Reply #10 on: August 13, 2017, 18:03:00 pm »

Having working in aircraft industry I can tell you the only allowed aluminum for structural welding is 2023 (in only some cases) and 6061 (it is allowed by FAA, and to be welded by someone with FAA certification), 7075 is no-no,Period, It becomes brittle and it cracks. Wink    

I seem to recall there are some laboratory laser welding methods for 7075, but nothing even an above average welding shop will have available.  I used to just say 7075 can't be welded if asked.  However, I have had a few people give the nose in the air, "I'll ask a real welder," response.  Now I mentioned that there is some white paper on alternative exotic welding methods.    

6061 welds really nicely with 4043 wire.  Piece of cake, nice clean welds.  

5052 welds well with 4043 or 5356.  4043 sacrifices some corrosion resistance.  5356 is the standard for 5052.  5052 (deck and bulkhead) and 5086 (structural) are the norm for small marine applications.  My welds on 5052 tend to come out sooty looking, but it wipes off with a rag and looks good.  Maybe a little more liquid looking than welds in 6061.  I've read a lot about back chipping, back welding, and stress relieving marine welds in 5052, but not a single commercially built small boat (under 25') I have looked at has been done that way.  Its just fitted, welded, and rigged.  

I know absolutely nothing about aviation welding.  Most of my reading and experience is primarily in marine welding.  Some with general purpose use of 6061.  

If you want to talk to a great resource on more kinds of welding than anybody else I know talk with Ernie Leimkuhler.  He would need a full size text book to bind all his certifications.  He used to be a regular on the welding technology newsgroups on Usenet, but he finally got tired of the off topic garbage and I think he no longer participates on Usenet.  He does have a Facebook page, but I have not seen him post anything there in a while.  Still he was always more than willing to help people who asked. 



« Last Edit: August 13, 2017, 18:07:05 pm by Bob La Londe » Logged

Getting started on CNC?  In or passing through my area?
If I have the time I'll be glad to show you a little in my shop. 

Some Stuff I Make with CamBam
http://www.CNCMOLDS.com
Millone
Droid
**
Offline Offline

Posts: 76



View Profile
« Reply #11 on: August 13, 2017, 19:10:47 pm »

Thank you all for sharing your experiences.

I do not cut a lot of aluminium but when I do it, I use the 6061. I have installed a Noga Minicool air+liquid http://www.noga.com/nogaProducts.php?catID=moco which helps to lubricate and to clear the chips out of the cutting line.

I fully share the sentiment about the mist in the air. When I cut with the coolant for a couple of hours,  the workshop becomes really foggy and I have to ventilate it properly to avoid the problem. But I also understand that to cut fast and deep there are no alternative than to use the coolant and the air even if the single flute end mill helps quite a lot to avoid the aluminium to stick to it.

Thanks for the very exhaustive information.
Felice
Logged

"It doesn't matter whether you're the lion or a gazelle-when the sun comes up, you'd better be running.

Dan Montano
Garyhlucas
CNC Jedi
*****
Offline Offline

Posts: 961


View Profile
« Reply #12 on: August 13, 2017, 21:18:20 pm »

Try a Fog Buster style. I cut for hours too, no fog!
Logged

Gary H. Lucas

Have you read my blog?
 http://a-little-business.blogspot.com/
Bubba
CNC Jedi
*****
Offline Offline

Posts: 2202



View Profile
« Reply #13 on: August 13, 2017, 21:58:00 pm »

My coolant mister was build based on this. It does work well.

http://www.cnczone.com/forums/uncategorised-metalworking-machines/102934-built-fog-less-coolant-mister.html
Logged
Garyhlucas
CNC Jedi
*****
Offline Offline

Posts: 961


View Profile
« Reply #14 on: August 14, 2017, 02:42:26 am »

Yep that is what I built. I found that using a quick exhaust valve to pressurize the tank keeps it from dripping constantly when the air goes off.
Logged

Gary H. Lucas

Have you read my blog?
 http://a-little-business.blogspot.com/
Pages: [1] 2
  Print  
 
Jump to:  

Powered by MySQL Powered by PHP Powered by SMF 1.1.19 | SMF © 2013, Simple Machines

Valid XHTML 1.0! Valid CSS! Dilber MC Theme by HarzeM
Page created in 0.166 seconds with 19 queries.

Copyright © 2008 HexRay Ltd. | Sitemap