Cooling with HVLP as mist producer?

[Spartan117]

Hey guys,

i finished my "Karl_T-Fogbuster", but now i have a question:

Do your misters spatter, too?
I mean, it's doing very well and it doesn't need much coolant (i tested with water first), but it's some kind of spattering.

Is this what it is supposed to do?

I have the tank pressurized at 20psi, the air about 5-7psi. The nozzle is 0,04" (1mm). I built everything like shown on the plans from Karl.

Don't get me wrong, the mister seems to perform very well. I don't have any fog, only very small drops leave the nozzle and they have enough kinetic energy to go through the cyclone around the cutter, even at 40000rpm.

I'm just wondering if the spatter is how it should work. Otherwise maybe i could try to integrate a (hypodermic) needle into the tube, so the coolant leaves the needle right in the middle of the air. With pressurizing the cooland, there still should be the same small drops as before.

[Karl_T]

Hey guys,

i finished my "Karl_T-Fogbuster", but now i have a question:

Do your misters spatter, too?
I mean, it's doing very well and it doesn't need much coolant (i tested with water first), but it's some kind of spattering.

Is this what it is supposed to do?
...

This is the first I've heard of anyone building one on the other side of the big pond.

No, mine doesn't spatter. There must be some subtle design difference.

In general you need shear from high air velocity to break up droplets to a smaller size. Just for trial, what happens when you increase air pressure?

I copied the orifice sizes from the patent, not my design work. The patent claims orifice size to be critical.

I did break off my nozzle once. Turned the unit into a spitter. The replacment nozzle is 0.049" or 9 thou larger. It works great. Others have been using MIG welder gun tips.

I'd also look at orifice size at your combining block.

Karl

[Steve Seebold]

Did you debur the holes on the end of your spray nozzle? I looked at my FogBuster and the holes have sharp edges. A small chamfer could be what is causing your spatter.

[Spartan117]

Ha, now it works like it should.
Your comments led me on the right track, thank you

Look at the picture:




Here you can see the critical difference. On the left side is the original nozzle. Please ignore the different threads, i changed that before. This model was the only 1mm-nozzle i could get my hands on.

So, the point is the modified tip-design. The spatters were generated at the flat tip-surface (yellow arrow), because of the return-flow at the tearing edge. A drop developed and grew, until the air ripped it off as a spatter.

What i did:
I changed the tip-design (right nozzle) and now there is no more spatter at all

Thank you very much, Karl, this is exactly what i was looking for!

I hope my english is understandable enough to clarify the problem and it's solution?

But I'm still wondering how the original fogbuster works with only one regulator and the same pressure on the tank AND air...
I tried that too, but the pressure of the air seems to keep the coolant from getting to the mixing-block.

Anyone here that uses his selfmade-fogbuster with only one pressure on tank and air?

[Karl_T]

Ha, now it works like it should.
Your comments led me on the right track, thank you

...
Anyone here that uses his selfmade-fogbuster with only one pressure on tank and air?

We learned something. I average 1 email/ month on this. I'll pass on your knowledge.

My original was a copy of the henchforth patent with only one pressure. It worked by using a couple needle valves to restrict air flow. Then I tried two pressure regulators and got a HUGE improvment. That was 10 years ago now. I've not heard of any unit using one regulator working as well.

Karl

[Spartan117]

I must admit that i was VERY suprised how good it can be adjusted and how low the air-consumption is with the two regulators.

It can be used at 4psi air-pressure and it performs good anyway. The gauge of the compressor seemed to be nailed down^^

Maybe i can do some volume-tests in the tub, when my wife is away

[ddgman2001]

I have been using the Hench FogBuster since 2004. They are absolutely the best mister I have found to date.

I pressurize the tank with 40 PSI and I pressurize the nozzle with 6 to 10 PSI.

There is not much mist coming from the nozzle. Actually, if you can see the mist, that's too much.

I have the 1/2 gallon dual nozzle mister on all 3 of my machines, and that amount of coolant will last about 2 weeks when I work about 6 hours a day.

I'm trying to decide between one and two nozzles. It seems like a one nozzle setup could only cool two edges of a profile leaving the other two to gall up. Is that correct or am I missing something?

[Nava]

I just finally finished my HFFB today and I must say Im totally blown away just how well it works. I was using WD40 air blasts and a vac before this(needed an extra arm) and all I could manage was about 1mm DOC in 6060 with an 8mm endmill. Now I can manage to get a 10mm DOC and the machine seems pretty happy.

Thanks to all of you for posting how you made your own.

[AirChunk]

I like this . I gotta build one!