MQL system (compare to fog buster)

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Sep 4, 2019
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North Carolina
I mentioned in another thread recently that I have been sidetracked yet again from one project into another. This time, I diverted from my ongoing foundry build for a relatively quick project, making a minimum-quantity-lubrication system of the sort patented under the Fog Buster name. Here is what I came up with - understand that the short tubing was only temporary, for testing purposes.

A couple of key points: I used a SodaStream bottle that is past its "discard by" date as the basis, in part because I will use only a small amount of coolant over time (especially in an MQL system), and in part because I had it on hand. The ball valve, brass pickup, and loc-line-clone came from an ultra-cheap mist coolant system from Amazon. Not visible here is that the loc-line is not actually conveying the coolant and air; rather, there is a tube of around 2mm ID that carries the stream from the aluminum valve block up to a brass nozzle hidden inside the loc-line, also from the same mist coolant system. Also not particularly visible is the fact that the aluminum piece that fits over the SodaStream bottle actually fits snugly down into it, extending into the bottle by around 10mm. It may not be necessary, and certainly it does not seal the bottle, but it does provide a very positive and stable connection when combined with the screw cap. The black screw cap is 3d printed for ease of manufacture, and seems to be more than adequate for the job - though of course, it could be machined instead as long as one doesn't mind making the double-start threads. Finally, one more thing that is not readily visible is the sealing gasket between the aluminum insert and the bottle; at first I was going to use an o-ring, but before purchasing one of the requisite size, I decided to see if a 3d printed washer made from TPU-85 would do the job - and somewhat to my surprise, it works perfectly.

All in all, this was a quick and inexpensive project, and it seems to work exactly as intended. I can provide plans if anyone wants them - and if it is okay to do so. (Does anyone know if the Fog Buster patent has expired?)


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I'd sure like to see your drawings! All the "Fog Buster" plans I've seen have been the straight brass tube style of spray head, and your set up looks good. I already use air blast to clear chips, but have not integrated an MQL head. Mist is really a pain unless you can capture the air born residual mist.

i like your MQL system Awake. nice design. i hear your issues with needle valves. in your video, your initial adjustments
appeared to "drift". I.E. the density of the mist cloud seemed inconsistent.

when i was doing neon, i encountered the same problem with needle valves. the valves i used tended to have
a lot of backlash, and would not maintain a consistent flow rate. the valve stem packing ("gland nut" ??)
tended to have "memory" (the valve packing would "relax" after adjustment and cause the valve setting to drift).

precision needle valves might be available at a laboratory supply company (Boston Scientific?) or a neon sign
supply shop. might be worth a try.

Thanks, Paul. As I was editing the video and seeing it again, I was thinking there might be some delay in the response, especially at such fine adjustments - I was thinking perhaps I need to adjust, then wait a few seconds before deciding whether the adjustment is what I need. But your explanation also seems plausible. Definitely more experimenting to do ...
And here are the plans. I've attempted to produce both a metric and an inch version ... but the truth of the matter is, the design is a mixture of both! I've also included the .stl files of the bottle cap and the TPU seal. Enjoy!


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I neglected to include the .stl file for the little clips that hold the tubes together. These have worked really well! The .stl file is attached.


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one thing to consider is that the mist is not good for you to breathe, so you want positive ventilation to take the mist and the vaporized oil from the work away rather than filter the air through your lungs.
Not in any way trying to take away your efforts, but it looks similar in concept to John Bogs' original idea.

Spraymist 03.jpg
Spraymist 04.jpg
Spraymist 07.jpg
Spraymist 11.jpg
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Spraymist 35.jpg

There are 39 pics of JB's design. He only ever made rough sketches of his designs but they were good enough to follow. If anyone wants copies of the other pics, I can forward them on, or post them here (or even make a separate thread) if it doesn't upset Awake.

The Emerald Isle
Hi Dave,

No upset here! And I hope my post didn't come across as claiming any originality for the idea of an MQL system. On the contrary, the basic design is patented by FogBuster, I believe. There are also a number of different plans on the internet for various designs based on this concept, and I of course consulted several. The only thing I take any credit for (not much) is the particular (or maybe peculiar!) implementation that I came up with, using a SodaStream™ bottle with a 3d printed cap and gasket.

Just as a note - it looks like most of the design you have shown is actually for a venturi system - which will generally equate to a mist coolant system, rather than an MQL. (That may just mean that I have not fully understood the design you have shown!)
i like your MQL system Awake. nice design. i hear your issues with needle valves. in your video, your initial adjustments
appeared to "drift". I.E. the density of the mist cloud seemed inconsistent.
precision needle valves might be available at a laboratory supply company (Boston Scientific?) or a neon sign
supply shop. might be worth a try.
Hi Gents, I once had a guy needed a needle valve - I suggested he went to a Model Aircraft shop and bought one for a carburettor. He bought one for "small change2 and it worked fine! He needed to calibrate a pressure decay leak detector, so fitted it into a part and was able to adjust it to simulate a leak of one air bubble per minute. (in the air-under-water test tank). Then he used that part with the "leak" to be detected by the pressure decay tester, so it passed a part with zero bubbles in 15 minutes, and failed a part at 1 bubble per minute. Very good precision from such a cheap part.
Dave, I went back to see what I had consulted as far as plans. Best I can tell, I didn't find (or at least, didn't download) any actual plans, but rather only viewed YouTube videos of several folks who had made a DIY MQL system. (The key to finding these on YouTube, though, is to search for "DIY Fog Buster" - people tend to use the trademarked name rather than the generic description MQL = minimum quantity lubrication.) I don't see anything from John Bogs in that search, so I am guessing I did not see any of his plans. But the basic concept, developed by (or at least patented by) Fog Buster, is pretty simple: split the air feed so that one branch pressurizes the coolant canister, thus feeding pressurized coolant to the working end; use a needle valve there to regulate how much of the pressurized coolant is fed into the air stream. There's only so many ways to accomplish that ...