I have used both and could not tell one from the other looking at the results.
Amana does recommend more aggressive DOC, and you may be able to pull off using their recommendation, but indeed they tend to provide values for more rigid machines than a SO3. (SO5/HDM is a different story, I could not comment on those). My crowd-sourced rule of thumb is to limit depth per pass to 5-10% of the endmill diameter in aluminium. Multiple people have reported that on a SO3, you are better off using low DOC, and compensate with higher WOC and feedrate. There’s a great video from @Vince.Fab on this.
3 Likes
And also, using air assist to get the chips out of the slots, I use air and alcohol when cutting aluminum.
2 Likes
Most of the Aluminium I can get over here is stress relieved tempered T6XX so I wouldn’t say that T651 is not T6, rather that it’s a specific subtype
https://www.aalco.co.uk/datasheets/Aluminium-Alloy_6082-T6~T651_148.ashx
Says:
"Temper Types
The most common tempers for 6082 aluminium are:
T6 - Solution heat treated and artificially aged
O - Soft
T4 - Solution heat treated and naturally aged to a substantially stable condition
T651 - Solution heat treated, stress relieved by stretching then artificially aged
"
So the difference seems to be that 651 is stretched inbetween heat treatment and ageing.
6082 is what we get over here instead of 6061.
2 Likes
Avoiding the chips being recut or the workpiece getting hot is key, as you’ve discovered, when Aluminium gets warm it gums up the cutter. Feed speed, air blast and lubrication all help with this. If you’re going air blast then a mister or fogbuster (or an eBay knock off) are well worth it.
In terms of cutter, the ZrN coated C3D cutter will resist aluminium sticking to it better than an uncoated cutter. I’m informed that one should avoid anything with Al in the coating as that will stick to the Al in the workpiece very quickly. I’ve had good luck with DLC coated as well, even been able to peel gummed in Al off the cutter and go again without resorting to chemicals.
4 Likes
Thank you all again, the support and community rocks!
1 Like
I cut quite a bit of aluminum. Well, actually I have kids on my robotics team that do almost all of the CNC running to cut aluminum. Almost all of it is slotting as we are cutting from sheet aluminum parts for the robot. Some of the parts are then bent on the brake after cutting.
Our standard recipe is
1/8" single flute bit (cheap 10 pack of HQMaster from Amazon)
0.01 to 0.015" depth per pass
35 ipm (sometimes bumped by 10%)
16K RPM (slowest on the Dewalt router)
Dust shoe with vacuum - moves air and keeps chips out of the slot.
I think we can do more per pass but haven’t experimented on this yet
The holes we mill are usually 0.15". Once in a while will use adaptive clearing for a small pocket. All the outlines of the parts is just slot cutting and that ends up being probably 80-90% of the cutting time.
Now when we do occasionally cut something thicker like you have we will use a cheap mister with denatured alcohol. This cools the aluminum and keeps it from getting gummy. We always have a small spritzer bottle of denatured alcohol next to the machine. If the part feels even slightly warm to the touch it gets a couple of sprays. The rapid evaporation cools it quite well such that it feels cool to the touch.
Julien mentioned using a loupe to check your bit and I heartily agree. We’ve had several times where things aren’t cutting right. Swap the bit and it starts cutting better. Inspect the old one and the very tip of the end mill is chipped.
4 Likes
DanO - Thank you! Wow lots of great info here 
Same situation here, I’m making aluminum sheetmetal stuff for our robot.
Do you find the vacuum is enough to remove chips? You use the normal setup with the vacuum sucking up the chips?
I haven’t dared try this yet, I am still a bit nervous cutting aluminum, and it’s nice being able to see the cutter. I have rigged a reversed vacuum in the boot so that it is blowing at the cutter.
Also, those speeds and feeds are just about what we came to when testing stuff (although we do 22k rpm) which is good to hear!
Why 6061 for heat sink? 6061 is a strong alloy, was once known as an aircraft skin alloy. maybe a softer alloy such as 1100 O temper would work better as a heat sink if strength is not a factor.
Softer is worse as far as machining goes. Most alloys gum up and anarchy ensues. 6061 was specifically alloyed to be as machineable as possible.
3 Likes
I have an XXL w/ HDZ and 2.2kw er 20 spindle. Used for roughing an O-flute 1/4"(LMT Onsrud) at 19k and 60 IPM at .030" DOC. I misted with some wd40 silicon spray, pretty messy, but heat is a killer. Finished with a 2-flute 1/8" and a 15deg tapered ball. Could not hear the cutter, only sound of vac. 6061AL. 2 or 3 fluter will not allow chip evacuation without flood coolant or high pressure air etc. I agree with statements that you have to feed aggressively enough to cut the material, otherwise you are plowing. Less time in cut equals less heat.
10 Likes
I got my air / mister setup. Going to try it with just air, but I can easily add water or alcohol to it.
Quick questions if I do:
- I have Isopropyl Alcohol, but Denatured Alcohol - does the type matter? I see references to both on here and elsewhere.
- Is a 50/50 mix of Alcohol and Water good?
- Likelihood of fire? Lol
- If I also have a wet/dry vac sucking up some bits with the Alcohol in the air - any risk there?
Master @Vince.Fab uses a 50/50 mix of water and alcohol and he says that’s safe:
With so little being sprayed, it will evaporate rather quickly anyway
2 Likes
I use my thumbnail to adjust the mist. Turn on the air, then start to ease up the coolant until it just starts to form tiny little droplets on your thumbnail (Or a piece of dry paper works too.)
My cheap system tends to ‘drip’, intermittent puffs of coolant every ~half second rather than a constant mist. If I position my eye so there is a dark background I can see the puffs.
I put a drop of blue loctite on the coolant screw then wiped most of it off to keep it from vibrating & moving.
2 Likes
Sorry Madelyn about taking so long to reply…
Awesome to hear you are also doing stuff for robotics! My team is FTC #10273
The end mill tends to throw chips out of the groove but they’ll settle back in if there isn’t a vacuum. With the vacuum they just get sucked away. I use a PwnCNC v2 dust shoe with a Fein Turbo I vacuum. With this dust shoe the vac connection is on the backside so there is reasonably good view of the cutter and if you take off the front part of the dust shoe there is really good view and still acceptable cleanup of chips.
It doesn’t really matter what type of alcohol. Denatured is generally cheaper which is why I use it. Isopropyl is literally sold to be rubbed on the skin so it has less toxicity than denatured (which is mixture of ethanol and methanol.) But denatured is not really that toxic either - just don’t go drinking it.
If Vince says 50/50 mix - go with what he says. I use just straight denatured as it’s quick and easy and does the job.
Yes - alcohol can burn. But you have to get quite a bit of it. I did some experiments when I was thinking about the risk of it. When I pour alcohol on the plate I can sometimes get it to start burning when I use a lighter. But it aint easy. I have sprayed it into the air both with my mister and with a sprayer bottle - I can’t get that to ignite even using a propane torch. (I was kind of hoping to make a nice fireball but no luck).
When using it with the vacuum you don’t even notice the odor in the air when walking into the room. The amount of alcohol to amount of air just dilutes it so much there isn’t any problem.
3 Likes
All, just wanted to say thank you! Got my air assist going with a 50/50 mix of water and alcohol. Cut great, lots of slotting, some pocketing, chamfering, set it for 18,000 RPM and 35 inches per minute, ended was comfortably running at 30%+ for most of the cut.
Looks better in person, the phone camera likes to “enhance” the detail
13 Likes
Think you nailed it!
This topic was automatically closed 30 days after the last reply. New replies are no longer allowed.