Air Compressor for CNC Mill?

ProjectZero · Dec 7, 2016

Hey guys,

As I mentioned in another thread we've got a 2005 Fadal VMC 3016. I was blanking on needing a compressor to go with it. According to a datasheet I found online we need 80-90PSI with a momentary SFCM of 15. We grabbed the only air compressor we had lying around the machine shop, a pancake compressor from home depot (6 gal, 2.6SFCM at 90 PSI). Besides being loud as hell and coming on pretty often, it worked just fine, despite having an SFCM that's a fifth what I'm supposed to have.

So my question is, just how low can I get away with in terms of volume in gallons and SFCM? I'd like to get a nice quiet air compressor like this Dewalt 200PSI (2.6 Gal, 3.0 SFCM) but I'm worried there's some lower limit I'm going to cross. Maybe the only reason my current air compressor is working is because the 6gal is enough to give it that momentary required sfcm for a tool change.

I've found some great older threads about mills and air compressors on this forum (like this one ) but still needed a bit more opinion! This compressor will be exclusively for the mill.

Kallam · Dec 7, 2016

Amazon.com: California Air Tools Ultra Quiet: Tools & Home Improvement

I have a 1 hp California quite air compressor model 2010a 2 gallon tank
on my 2412 sharp cnc mill. You most likely need a 2hp
Can't beat them I have had mine for about 2 years
you can hardly hear it at 60 db .

jCandlish · Dec 8, 2016

Don't forget a dryer.

Those rusty bearings were adjacent to the wet drawbar exhaust.

Brian · Dec 8, 2016

I'll second the California Air Tools unit, I have the 2hp 10 gallon version and it works great. I run an old Milltronics CNC with an air drawbar, although no air blast.... but I also use it to run my MQL coolant system and it keeps up just fine.

Guest · Dec 8, 2016

Remember you want the compressor running 50% of the time or less, if your shop is on the warm side in the summer probably better get that down to 1/3 of the time. Any more than that and it will likely have a short life.

gkoenig · Dec 8, 2016

I third the California Air Tools 10 gal unit.

BobM3 · Dec 8, 2016

It could be that the peak flow is during a spindle blow on a tool change. You only need that for a short period of time. If you have a long enough air hose then the hose might by acting as an accumulator storing compressed air.

aarongough · Dec 8, 2016

Air usage on a Fadal is pretty minimal.. There's no air purge through the spindle so the only times air is used is for actuating the spindle orientation cyliner, actuating the tool release cylinder and for the air blast through the spindle when changing tools. To supply those needs you can definitely get away with a small compressor like a pancake compressor.

However if you're machining a lot of steel you'll likely find that you'd like to have an air blast running during cutting rather than coolant, and that will use a lot more air. I have a 5HP dual stage compressor with 80 gallon tank. It's rated for 18CFM @ 150PSI and comes on for about 2 minutes every 15 minutes or so while I'm running production cutting tool steel.

Whether you'll need an air drier or not depends on your climate and the size of the compressor you end up getting. I don't run a drier, I run a water separator right at the compressor, then about 30ft of air hose to the VMC and then another water separator/filter unit on the manifold that I have for supplying air to the CNC. I've never seen any water in the separator on the CNC, only water in the separator attached to the compressor. I have also had the tool release cylinder apart a bunch of times with no sign of moisture anywhere.

ProjectZero · Dec 8, 2016

aarongough said:
Air usage on a Fadal is pretty minimal.. There's no air purge through the spindle so the only times air is used is for actuating the spindle orientation cyliner, actuating the tool release cylinder and for the air blast through the spindle when changing tools. To supply those needs you can definitely get away with a small compressor like a pancake compressor.

However if you're machining a lot of steel you'll likely find that you'd like to have an air blast running during cutting rather than coolant, and that will use a lot more air. I have a 5HP dual stage compressor with 80 gallon tank. It's rated for 18CFM @ 150PSI and comes on for about 2 minutes every 15 minutes or so while I'm running production cutting tool steel.

Whether you'll need an air drier or not depends on your climate and the size of the compressor you end up getting. I don't run a drier, I run a water separator right at the compressor, then about 30ft of air hose to the VMC and then another water separator/filter unit on the manifold that I have for supplying air to the CNC. I've never seen any water in the separator on the CNC, only water in the separator attached to the compressor. I have also had the tool release cylinder apart a bunch of times with no sign of moisture anywhere.

Thanks a ton for the info everyone. This loud pancake compressor (82db) is driving me nuts so I'm definitely going to get on that California Air Tools compressor. I'm looking at this guy. 2hp 10 gal, I can save some money by dealing with the manual drain, it shouldn't be too bad to drain it every couple times I use the mill.

The dryer was something I did not know about and you've definitely got me thinking. I live in northern california, it's a fairly temperate climate. The machine will only be running an hour or two a day, so I might pass on it for now and keep it in the back of my head for if we start ramping up our light prototyping.

Edit: I'll start with an in-line filter like this guy here.

aarongough · Dec 8, 2016

ProjectZero said:
Thanks a ton for the info everyone. This loud pancake compressor (82db) is driving me nuts so I'm definitely going to get on that California Air Tools compressor. I'm looking at this guy. 2hp 10 gal, I can save some money by dealing with the manual drain, it shouldn't be too bad to drain it every couple times I use the mill.

The dryer was something I did not know about and you've definitely got me thinking. I live in northern california, it's a fairly temperate climate. The machine will only be running an hour or two a day, so I might pass on it for now and keep it in the back of my head for if we start ramping up our light prototyping.

Huh... For that price I might consider the same compressor to take over running my mill... Beats having to build a soundproof enclosure around my current compressor...

ProjectZero · Dec 8, 2016

Yea really. Now I'm trying to see if I can't get away with one of the 60 db versions. That's half again as quiet (4 times quieter than the 82db nightmare I'm using now), but at 1hp and 2-5 gallon tanks, I'm worried I'd get too greedy and cross that threshold where it can't supply enough air to my machine.

aarongough · Dec 8, 2016

ProjectZero said:
Yea really. Now I'm trying to see if I can't get away with one of the 60 db versions. That's half again as quiet (4 times quieter than the 82db nightmare I'm using now), but at 1hp and 2-5 gallon tanks, I'm worried I'd get too greedy and cross that threshold where it can't supply enough air to my machine.

Yeah and one thing to be aware of is that the Fadals don't have air pressure sensors... Which means the machine will try to change tools even if the air pressure is low or if the air-line is not even connected!

It will change tools just fine down to 80PSI or lower, but keeping air pressure up is better.

It shouldn't damage the machine (usually) if you do try to change tools with low air pressure. The orient cylinder will likely still work (machine will alarm out if it doesn't). If the pressure is not high enough to release the tool it will pull the carousel wheel up and trigger an alarm. I've done it on my machine accidentally with no harm after forgetting to connect the airline, but not something I would like to do again if I can help it.

norb · Dec 8, 2016

Do yourself a favor and spend the money on a Kaeser screw compressor. They are very quiet and well worth the expense.

aarongough · Dec 8, 2016

norb said:
Do yourself a favor and spend the money on a Kaeser screw compressor. They are very quiet and well worth the expense.

Sure, for the low low price of $7k or more... I love the idea but buying a screw compressor just doesn't make sense for anyone on a small budget. Reciprocating compressors are reliable as hell if you buy a good one, and building an enclosure around one to quiet it down doesn't take much time.

ProjectZero · Dec 8, 2016

aarongough said:
Sure, for the low low price of $7k or more... I love the idea but buying a screw compressor just doesn't make sense for anyone on a small budget. Reciprocating compressors are reliable as hell if you buy a good one, and building an enclosure around one to quiet it down doesn't take much time.

Needless to say we're on a small budget so while I'm sure it's a great machine, that doesn't make sense for us.

I might risk the 60DB version. After all, it goes up to 120 PSI and I only need 80-90. It has the same SFCM at 90 DB and volume as the pancake compressor I'm using without incident now. If worst comes to worst I'll return it for the much-lauded 2hp 10gal version that several people have recommended.

ProjectZero · Dec 8, 2016

ProjectZero said:
Needless to say we're on a small budget so while I'm sure it's a great machine, that doesn't make sense for us.

I might risk the 60DB version. After all, it goes up to 120 PSI and I only need 80-90. It has the same SFCM at 90 DB and volume as the pancake compressor I'm using without incident now. If worst comes to worst I'll return it for the much-lauded 2hp 10gal version that several people have recommended.

Ok scratch that haha. I just ran my first test piece on the machine with a technician holding mny hand. My 6gal compressor was on entire time and he said I definitely needed to get a compressor with a bigger tank or I'd burn the thing out. He recommended 100 gallons....I'll at least get the 10gal California Air Tools. But I definitely won't be going with anything less than 10 gallons.

Bobw · Dec 8, 2016

ProjectZero said:
He recommended 100 gallons....

The cigarette paper guy?? Fadal's don't eat much air at all.

I've been running qty2 20 gallons tanks until I get around to fixing my big compressor, and that
runs 3 Fadals with ease, and I'm only coming up to 120psi. approx 7 minutes off, 2-3 on..

It wouldn't hurt to keep your eye out for blown up 20 gallon compressor, just for the tank. The
cheap chinese tool store (which sadly sells some decent tools) has a 21 gallon compressor reg 179,
(always on sale for 149-155) that would give you a backup and extra capacity. Not the quietest thing,
but the extra capacity will come in handy if you are using an air blast... That can eat up a lot of air FAST.

dkmc · Dec 8, 2016

norb said:
Do yourself a favor and spend the money on a Kaeser screw compressor. They are very quiet and well worth the expense.

And if you can possibly see thru the hype and hoopla, save yourself a lot of
money and DON'T drink the "Kaiser Koolaid".
Spend a fraction on a nice Quincy 3 to 5hp piston compressor, pressure lube type....

Kallam · Dec 8, 2016

The size if the tank doesn't matter.
If you add up the volume of the tool change air cylinder and the carousel air cylinder maybe 1/2 gallon.

Gallons don't matter the only thing that matters is out put the compressor.

I have a 3 hp compressor with a 60 gallon tank
I was loud 90db I couldn't stand the noise any more and the compressor ran alot i figured the valves may be going bad.
So i bought one of those California quite air compressors the 1 hp with a two gallon tank.
I figured if it was not big enough add a tee in the air line and add another one. 2x 1hp compressors
are $100 cheaper than one 2hp compressor.

But Just 1 compressor ran my mill just fine.

Corym · Dec 8, 2016

norb said:
Do yourself a favor and spend the money on a Kaeser screw compressor. They are very quiet and well worth the expense.

He should drop $7k+ for a compressor to power one VMC?

Uhh nope. That would be the biggest waste of money ever.

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