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mist jet system

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Ben Solon

Sat Jan 19 2013, 12:38AM

Registered Member #3900 Joined: Thu May 19 2011, 08:28PM
Location:
Posts: 600

To be brief, I've expanded the use of my CNC to cut al, and unless I cool the milling bit, it'll heat up, wear out, fuse, cause the gantry to vibrate, and other silly things. It's a pain in the @$$ to sit there dumping cutting oil down the bit all day long, so i've been working on a liquid cooling system. it's a small machine that needs lubrication at the cutting edge more than anything else, so I've opted towards a mist jet method. Today at robotics I tried to throw something together as a prototype using the pnuematics stuff, and got it semi-working with the system shown below...

The problem I've been having have been with the point where the gas and fluid mix. When the fluid reservoir is left open to air at the top and bottom, the water simply drips irregularly through the jet causing sputtering of mist. Some water even backtracks down the tube toward the compressor a bit. When the top of the fluid reservoir is pressurized, the nozzle is blocked, and a constant stream of fluid is pushed.

Does anyone have any info on how I could mix the two properly in order to get a constant flow of mist?

Much appreciated,
Ben

Ash Small

Sat Jan 19 2013, 01:09AM

Registered Member #3414 Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245

Take a look at carburettor technology. All you need is a venturi and a 'jet' from the top of the resevoir.

You could probably adapt the carburettor from an old, small motorcycle, or similar small internal combustion engine.

I assume you are re-cycling the coolant. You then just need a filter and small pump to feed back to the 'tank', with gravity feed to the float chamber.

EDIT: Another alternative is to adapt an airbrush.

macona

Sat Jan 19 2013, 01:17AM

Registered Member #3272 Joined: Mon Oct 04 2010, 11:40PM
Location: Beaverton, OR
Posts: 101

I use Bijur Spray-Mist systems on both my CNC mill and lathe. They work great. You do NOT want a venturi system. They make a ton of airborne mist that is not good to breathe.

There are plans out there on how to make the micro drop systems like the Bijur or Trico systems. They use a pressurized container that puts pressure on the coolant which delivers it to the tip. Here is one:

Ben Solon

Sat Jan 19 2013, 01:20AM

Registered Member #3900 Joined: Thu May 19 2011, 08:28PM
Location:
Posts: 600

*Off to rip apart the old leafblower in the basement!

edit: i've come to terms with that situation. i'm doing so much modding to the machine that right now i think i'll just mount it to an x shaft box containing all the coolant and non machining components. that way i can just box around it was well to seal it up and filter the air in and out with a fan and some fabric above a drip collector. but I'll still consider each suggestion equally. i saw some of those on ebay as well, but i thought they where flood cooling.they're a bit expensive as well, but so are all the other micro droplet systems i've seen.

macona

Sun Jan 20 2013, 12:31AM

Registered Member #3272 Joined: Mon Oct 04 2010, 11:40PM
Location: Beaverton, OR
Posts: 101

There used to be a guy who sold the Bijur tanks new for $80. He is now asking $250, looks like he got wise!

You can still pick them up used for about 80 to $100. Well worth it, they are very well made. The tank is cast aluminum, has the regulator and a solenoid valve built in. There is another guy on ebay who sells the nozzles for $60. This is a great price. Build your own tank but use these nozzles, it will save a lot of hassle.

BTW, it is not that your bit is wearing and getting dull, Aluminum likes to weld itself to the cutter. Even a brand new cutter can load up in seconds if you cant get the chips out of the way fast enough. Even directed air at the cutter will help keep this from happening.

Ash Small

Sun Jan 20 2013, 06:38AM

Registered Member #3414 Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245

macona wrote ...

You do NOT want a venturi system. They make a ton of airborne mist that is not good to breathe.

That's a good point Macona, but Ben specifically stated he wanted to spray a mist. Any mist will produce airborne particles.

The system I use on my lathe consists of a pump from a washing machine, connected to a tank, with a tap to control the flow. I just aim a jet of coolant at the cutting tool. My lathe was built in the 1800's, and was originally treddle operated, before I converted it to electric power. I rigged up an old stainless steel kitchen sink underneath to catch the coolant, with plumbing from the plug hole to return coolant to the tank underneath.

ConKbot of Doom

Tue Jan 22 2013, 05:35PM

Registered Member #509 Joined: Sat Feb 10 2007, 07:02AM
Location:
Posts: 329

Around a machine shop? got any safety air nozzles with the holes in the side so bad stuff wont happen if the exit gets clogged?

stick a straw/tube in the hole on the side and tape it in place, put the tube in a cup of your liquid of choice. The suction is more than enough to draw the liquid up, no need to gravity feed. just add a needle valve.

Obviously this can be refined, but I think you get the idea.

macona

Thu Jan 31 2013, 09:42AM

Registered Member #3272 Joined: Mon Oct 04 2010, 11:40PM
Location: Beaverton, OR
Posts: 101

Ash Small wrote ...

macona wrote ...

You do NOT want a venturi system. They make a ton of airborne mist that is not good to breathe.

That's a good point Macona, but Ben specifically stated he wanted to spray a mist. Any mist will produce airborne particles.

The microdrop systems are still considered a mist system. They serve the same purpose, not to be a flood system. The microdrop systems use a lot lower pressure air so they dont atomize like a venturi system does. I used one of the generic mist system on my table saw and it would create a fog around the say. The microdrop (Bijur Spraymist) systems I have on my cnc lathe and cnc mill do not have this problem.

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