AIR BLAST For Steel Milling

I was milling some parts yesterday on the Hurco. Some steel parts. I
was using AlTin coated carbide mills. The parts looked ok, and the
chips looked good. Mostly blue with a few silver chips. The parts were
not getting excessively hot, but after a while I could see a dull glow
coming off the mill. That kind of bothered me so I setup and air blast.
That had the added benefit of eliminating chip recutting. The thing
is to get everything I anted the air blast had to use a modestly decent
volume of air. The parts actually looked better and mills never reached
that glow again, even with long cut times.
Is an air blast like that common for cutting steel? Remember I have
been CNC machining for more than a couple years now, but 99% of the
parts I make are aluminum. Years ago I used to come on this group and
pester you folks about cutting aluminum parts faster and faster and more
If an air blast is useful for that sort of thing, what can I do to use
the air more efficiently. I have dismissed vortex tubes out of hand. I
have made one, and I have a commercial one, and they both waste a lot
more air than any benefit they might provide. Heck, you get some
cooling affect as the air expands out of any nozzle. I was actually
thinking about things like a better nozzle design on the air blast to
get a predictable cone of air, and making a ball mount with a slip clamp
to hold the air nozzle so it can be directed to exactly surround the tip
of the mill with its cone of air.
Reply to
Bob La Londe
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I would think using the ail to blow a mist would be a lot more efficient. But understand that mist might not be good thing with carbide.
Maybe use a hypodermic needle to use less air but direct the air better.
Reply to
efficient. But understand that mist might not be good thing with carbide.
Well, something along those lines, but I think that would not be nearly enough air to be useful. Even the nozzle from an irrigating syringe might be a little small.
Reply to
Bob La Londe
Air blast is indeed used for metal cutting. It not only removes chips but can keep the cutting tool cooler. This helps prevent chip welding. A cooler chip will often break sooner too, resulting in smaller chips. Eric
Reply to
No direct experience, just a comment from the peanut gallery. I don't think this air would need to go through your dryer, just use one of those water trap/pressure regulators at your mill installed just after a low spot with a drain valve.
Reply to
Other nozzle possibilities include mig welding tips, plasma cutter nozzles, and 3D printer extruder nozzles. The latter come in a nice range of sizes. For example, an Amazon $9.99 set of 28 has 2x0.2mm, 2x0.25mm, 2x0.3mm, 2x0.35mm, 10x0.4mm, 2x0.5mm, 2x0.6 mm, 2x0.8mm, 2x1.0 mm. A $3.22 ebay set (19pcs MK8 Extruder Nozzle) has 2x0.2mm, 2x0.3mm, 7x0.4mm, 2x0.5mm, 2x0.6 mm, 2x0.8mm, 2x1.0 mm. Those sets are all in brass. Hardened steel and ruby tip 3D nozzles also are available, costing about 10 times as much.
Regarding your air dryers, does the air blast need to be dry? If not you could plumb its air out beforehand, presumably lessening the dryer load.
Reply to
James Waldby
I made a convergent nozzle to experiment with air flow amplification by reaming the nozzle conical with a tapered D reamer. The reamer is a lathe turned 20 degree steel cone milled lengthwise to the D cross-section, and ground sharp, and the tip ground to a drill bit shape.The aluminum nozzle blank was step-drilled before reaming because the reamer doesn't cut freely, it has to be forced in.
Th outside of the nozzle is a somewhat steeper taper so it doesn't impede air drawn into the exit jet. I reamed it larger until I liked the result.
Reply to
Jim Wilkins
I wonder if it would be worth it to use a venturri at the nozzle to increase air volume.
Reply to
Bob La Londe
Yes, and if you can tap the compressor tank BEFORE the regulator, it certainly will be more efficient. The high airspeed from full pressure air is not required, but throttling the pressure is a waste of energy/compressor power. It'll be a trifle noisy, though; consider earplugs.
Lots of airguns use venturis (venturae?) anyhow, you might just find a suitable nozzle off-the-shelf.
Reply to
a suitable
Actually I have a venturi vacuum pump I was thinking about repurposing.
However routing a new line all the way around the shop and thru the machine room is not a quick short term answer as discussed in other posts.
Reply to
Bob La Londe
Side Note: I setup an old Venturi vacuum pump on a magnetic base for some steel milling on my middle weight CNC mill and it worked great. Work piece came off the machine barely warm after an hour of cutting. Same with the mill. Lots of blue chips. I had a pretty good stream of air, but the compressor didn't cycle on as often as with my straight pipe air blast. Both have a ball valve for flow control. Now to look at redirecting that vacuum port to reduce likelihood of picking up chips...
Reply to
Bob La Londe
You can use these tapered drill bits to make internally and externally tapered nozzles like I described, which are more efficient if you gradually open up the bore to allow only as much air flow as you need at full air line pressure, without an energy-wasting throttling valve.
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The external taper helps draw outside air into the flow, somewhat like the venturi aspirator but simpler to make.
Reply to
Jim Wilkins

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