A Question for You Air Only Guys

I needed to get a couple jobs done. The screws need to be replaced on the
Taig so I couldn't use its regular flood oil coolant setup until I fix it.
I used my smaller machine, rubbed a little Tap Magic on the work piece and
hit it with a blast of compressed air. When surfacing off the aluminum work
piece with a 1/4" end mill (largest that spindle will hold) it got pretty
hot, but it worked great when 3D carving with a 1/16 ball mill. I ran full
pressure off my compressor (125 PSI I think) and used a simple ball valve to
regulate flow somewhat, but I let it flow pretty heavily. So... how much
air do you guys use? Pressure? CFM?
My compressor ran continuously when I was running the mill. I'll be adding
an electric shut off valve to the air line to that cabinet, so my compressor
will shut off when I am done with a cut, but I was thinking if I could
consume less air and get a decent job I would add a flow and pressure
regulator too.

Reply to
Bob La Londe
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Speaking naively, because I don't do this, either: a pressure regulator may be the least necessary part. Just putting in a valve to let you throttle back the airflow will "regulate" the flow to the extent that the compressor is maintaining pressure. A regulator will let you keep the flow steady, which means that you'll conserve air when the compressor pressure is high (by not letting the flow increase at high pressure).
But I suspect that the two biggest things that will save air will be to find the minimum flow necessary to keep things cool, followed by that electric cut-off dingus that you're proposing.
Does anyone use augmenter tubes, to get more low-pressure flow from the naturally low-flow, high pressure stream out of a nozzle?
Reply to
Tim Wescott
Augmenter tubes? Like an expansion chamber?

Reply to
Bob La Londe
I use air nozzles that entrain air and they work well for blowing chips and such. They work using the Coanda effect. Much more effective than a regular air nozzle. quieter too. Eric
Reply to
etpm
Air blast is probably the worst way to remove chips and cool things. A really good nozzle can move the chips with less air flow, but it is still inefficient. A jet of flood coolant takes very little energy compared to a big air compressor.
Jon
Reply to
Jon Elson
Jon Elson fired this volley in news:fICdnY1 _gaeW1vvSnZ2dnUVZ snipped-for-privacy@giganews.com:
Indeed.
Additionally, it provides lubrication, and "spot cooling" at the specific areas (cutting edges) where air cannot impinge because of the pressure "buffers" that corners produce.
LLoyd
Reply to
Lloyd E. Sponenburgh
I just brush on a little bit of MSC cutting oil for steel or kerosine for aluminum. There is a noticeable but not serious difference between completely dry and lightly oiled, but no additional benefit from more oil as long as I run at HSS recommended cutting speeds.
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are for dry cutting.
The older $3 Enco end mills dull quickly unless run slower. Otherwise I haven't had heat problems on mild steel, 303, drill rod and graded bolt shanks.
Sometimes the super-duper tapping fluids give a better finish. I use them very sparingly to avoid the fumes.
jsw
Reply to
Jim Wilkins
Depending on the material being cut conduction can play a major factor as well. I discovered the same affect in reverse when trying to weld aluminum thicker than 1/4 inch. I had to preheat and weld short stretches in order to get it to weld properly.
While the micro spot of impact at the edge of the cutter may not be directly impacted by air cooling flow it most certainly will not build heat as much and conduct it up the tool and into the spindle to the same degree if both the work piece and the tool are being cooled.
Anyway, This machine will remain dry one way or another for the foreseeable future. If you have some thoughts on doing that I would be more than glad to hear them. Your insights are always educational.
Bob

Reply to
Bob La Londe
"Bob La Londe" fired this volley in news:BlM9r.9099 $ snipped-for-privacy@newsfe11.iad:
Bob, The only things I can recommend are to use fairly large-diameter piping and high pressure, ending in multiple small lamilar-flow jets that will increase the velocity, let you direct the flow close to the heating zone, and provide significant expansion cooling as they work.
The added velocity will also give you better chip clearance, and drive you out of the shop with noise -- so wear ear-gear.
LLoyd
Reply to
Lloyd E. Sponenburgh
Thanks Lloyd. That particular machine is inside an MDF cabinet which helps a lot for sound deadening. You have to raise your voice to have a conversation right next to it, but 15 feet away you can have an almost normal conversation even with the shop doors closed. It could probably be better, but I put lexan doors on the front rather than more MDF. Currently the air is just a 1/4" piece of copper tube fed by a 3/8 air line with a valve in between. It worked pretty good, but consumed prodigious amounts of air. I am looking at various air volume increaser jets etc. The compressor on the other side of the room is louder than the noise from the cabinet.

Reply to
Bob La Londe
"Bob La Londe" fired this volley in news:yyN9r.4410 $ snipped-for-privacy@newsfe17.iad:
You don't need volume (well... within limits), you need a combination of high velocity and expansion from the feed line.
A high-velocity lamilar jet of air will carry a prodigious amount of ambient air along with it, but most of the goal is to get it to impinge directly in the cut zone, then do most of its expansion work there. If the velocity isn't high enough, the expansion occurs before the stream gets to the work.
LLoyd
Reply to
Lloyd E. Sponenburgh
"Bob La Londe" wrote in news:XKq9r.7200$ snipped-for-privacy@newsfe16.iad:
You can get a lot more air flow with less CFM/PSI using the right nozzle:
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Depending on the nozzle, they claim over 40% reduction in air "costs". The bad news is that they still want 10 cfm at over 100 PSI.
Doug White
Reply to
Doug White
Greetings Bob, I have air nozzles made by two different makers but they both work the same. Air comes out of an annular groove at the base of a cone. No air comes out of the center of the cone. The air does focus to a point about 4 inches from the nozzle end. And both types of nozzles entrain lots of air so they are really good for removing chips. I wonder how well a pin point air blast close to the cutter along with a more diffuse air blast from farther away would work? One thing I am seriously considering is CO2 cooling. I've been reading some about super critical CO2 cooling systems being tried on machine tools. Apparently one of the advantages when cutting soft materials is that the cold makes the chip brittle (or at least not so soft) and more likely to break. The CO2 itself also acts as a cutting fluid. Eric
Reply to
etpm
Wowwie.. 1/4" is a big leak and not particulary high velocity nor an accurately aimed jet of cooling air.
If you terminate that 1/4" line with a threaded fitting, you can experiment with various line/tubing fittings to make an adapter for a more suitable tip which will enable you to direct a fine blast more effectively.
The cutting tool is already twirling around in air, so it's essentially fanning itself. The aluminum workpiece is sinking away heat from the tiny contact area being cut.
So, I believe the most benefit that can be attained from an accurately aimed blast of air, would be chip evacuation, and not so much a cooling method.
The energy cost and wear of the air compressor would be significant with a 1/4" orifice/air blast. Getting the hole size down into the decimal range under 1/16" would probably be effective.. possibly two small blasts depending upon how the table traverses, so that a path is also kept clear ahead of the cutting tool.
You can experiment with various tip shapes without needing to get too technically involved into concentrating a pinpoint blast, which is basically the opposite of most commercially available sprayer tips for various fluids. Tiny tubing can be gotten from aerosol products that supply those extension wands for squirting the stuff into confined areas.
A tiny orifice hole with a tapered hole behind it, to accept an adjustable needle valve/screw may be all that's actually needed. How deep the straight hole is (beyond the tip of the needle point) will likely be the determining factor for the shape or concentration of the air blast.. WAG.
Testing air streams ain't so easy, but some sawdust may be helpful to see what's taking place. You may find that 40-80 psi will be very effective with small orifice sizes.
A smear of cutting lubricant may still be effective, as long as it isn't making the fine chips stick to the workpiece.
I'd suspect that recutting chips would be far more detrimental to performance than heat generated by the cutting tool.. JMG - just my guess, you'll be the best judge of that based upon what you can see.
Reply to
Wild_Bill
I was considering trying something as small as an athletic ball needle in my experiments. The 1/4" tube was a quick and dirty method and it worked for what I needed to do at the time.
Reply to
Bob La Londe
Broadcast station air booths, recording studio control rooms and such = are typically glazed using 2 layers of lexan or plexiglas with dead air = between...this arrangement blocks sound transmission remarkably well.
Reply to
PrecisionmachinisT

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